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Dorst KM, Engström O, Angles d'Ortoli T, Mobarak H, Ebrahemi A, Fagerberg U, Whitfield DM, Widmalm G. On the influence of solvent on the stereoselectivity of glycosylation reactions. Carbohydr Res 2024; 535:109010. [PMID: 38181544 DOI: 10.1016/j.carres.2023.109010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 12/11/2023] [Accepted: 12/11/2023] [Indexed: 01/07/2024]
Abstract
Methodology development in carbohydrate chemistry entails the stereoselective formation of C-O bonds as a key step in the synthesis of oligo- and polysaccharides. The anomeric selectivity of a glycosylation reaction is affected by a multitude of parameters, such as the nature of the donor and acceptor, activator/promotor system, temperature and solvent. The influence of different solvents on the stereoselective outcome of glycosylation reactions employing thioglucopyranosides as glycosyl donors with a non-participating protecting group at position 2 has been studied. A large change in selectivity as a function of solvent was observed and a correlation between selectivity and the Kamlet-Taft solvent parameter π* was found. Furthermore, molecular modeling using density functional theory methodology was conducted to decipher the role of the solvent and possible reaction pathways were investigated.
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Affiliation(s)
- Kevin M Dorst
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91, Stockholm, Sweden
| | - Olof Engström
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91, Stockholm, Sweden
| | - Thibault Angles d'Ortoli
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91, Stockholm, Sweden
| | - Hani Mobarak
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91, Stockholm, Sweden
| | - Azad Ebrahemi
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91, Stockholm, Sweden
| | - Ulf Fagerberg
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91, Stockholm, Sweden
| | - Dennis M Whitfield
- Sussex Research Laboratories Inc., 100 Sussex Drive Suite 1120B, Ottawa, Ontario, K1A 0R6, Canada
| | - Göran Widmalm
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91, Stockholm, Sweden.
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Popadynec M, Baradaran-Heravi A, Alford B, Cameron SA, Clinch K, Mason JM, Rendle PM, Zubkova OV, Gan Z, Liu H, Rebollo O, Whitfield DM, Yan F, Roberge M, Powell DA. Reducing the Toxicity of Designer Aminoglycosides as Nonsense Mutation Readthrough Agents for Therapeutic Targets. ACS Med Chem Lett 2021; 12:1486-1492. [PMID: 34531957 DOI: 10.1021/acsmedchemlett.1c00349] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 08/04/2021] [Indexed: 11/29/2022] Open
Abstract
A significant proportion of genetic disease cases arise from truncation of proteins caused by premature termination codons. In eukaryotic cells some aminoglycosides cause readthrough of premature termination codons during protein translation. Inducing readthrough of these codons can potentially be of therapeutic value in the treatment of numerous genetic diseases. A significant drawback to the repeated use of aminoglycosides as treatments is the lack of balance between their readthrough efficacy and toxicity. The synthesis and biological testing of designer aminoglycoside compounds is documented herein. We disclose the implementation of a strategy to reduce cellular toxicity and maintain readthrough activity of a library of compounds by modification of the overall cationic charge of the aminoglycoside scaffold through ring I modifications.
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Affiliation(s)
- Michael Popadynec
- Ferrier Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Alireza Baradaran-Heravi
- Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - Benjamin Alford
- Ferrier Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Scott A. Cameron
- Ferrier Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Keith Clinch
- Ferrier Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Jennifer M. Mason
- Ferrier Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Phillip M. Rendle
- Ferrier Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Olga V. Zubkova
- Ferrier Research Institute, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Zhonghong Gan
- Sussex Research Laboratories, Inc., 100 Sussex Drive, Suite 1120B, Ottawa, Ontario K1A 0R6, Canada
| | - Hui Liu
- Sussex Research Laboratories, Inc., 100 Sussex Drive, Suite 1120B, Ottawa, Ontario K1A 0R6, Canada
| | - Oscar Rebollo
- Sussex Research Laboratories, Inc., 100 Sussex Drive, Suite 1120B, Ottawa, Ontario K1A 0R6, Canada
| | - Dennis M. Whitfield
- Sussex Research Laboratories, Inc., 100 Sussex Drive, Suite 1120B, Ottawa, Ontario K1A 0R6, Canada
| | - Fengyang Yan
- Sussex Research Laboratories, Inc., 100 Sussex Drive, Suite 1120B, Ottawa, Ontario K1A 0R6, Canada
| | - Michel Roberge
- Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
| | - David A. Powell
- Inception Sciences Canada, 210-887 Great Northern Way, Vancouver, British Columbia, V5T 4T5, Canada
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Affiliation(s)
| | - Jiatong Guo
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
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Hassan MI, Lundgren BR, Chaumun M, Whitfield DM, Clark B, Schoenhofen IC, Boddy CN. Total Biosynthesis of Legionaminic Acid, a Bacterial Sialic Acid Analogue. Angew Chem Int Ed Engl 2016; 55:12018-21. [PMID: 27538580 DOI: 10.1002/anie.201606006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Indexed: 02/03/2023]
Abstract
Legionaminic acid, Leg5,7Ac2 , a nonulosonic acid like 5-acetamido neuraminic acid (Neu5Ac, sialic acid), is found in cell surface glycoconjugates of bacteria including the pathogens Campylobacter jejuni, Acinetobacter baumanii and Legionella pneumophila. The presence of Leg5,7Ac2 has been correlated with virulence in humans by mechanisms that likely involve subversion of the host's immune system or interactions with host cell surfaces due to its similarity to Neu5Ac. Investigation into its role in bacterial physiology and pathogenicity is limited as there are no effective sources of it. Herein, we construct a de novo Leg5,7Ac2 biosynthetic pathway by combining multiple metabolic modules from three different microbial sources (Saccharomyces cerevisiae, C. jejuni, and L. pneumophila). Over-expression of this de novo pathway in Escherichia coli that has been engineered to lack two native catabolic pathways, enables significant quantities of Leg5,7Ac2 (≈120 mg L(-1) of culture broth) to be produced. Pure Leg5,7Ac2 could be isolated and converted into CMP-activated sugar for biochemical applications and a phenyl thioglycoside for chemical synthesis applications. This first total biosynthesis provides an essential source of Leg5,7Ac2 enabling study of its role in prokaryotic and eukaryotic glycobiology.
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Affiliation(s)
- Mohamed I Hassan
- Department of Chemistry and Biomolecular Sciences, Centre for Chemical and Synthetic Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | - Benjamin R Lundgren
- Department of Chemistry and Biomolecular Sciences, Centre for Chemical and Synthetic Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | - Michael Chaumun
- Department of Chemistry and Biomolecular Sciences, Centre for Chemical and Synthetic Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | | | - Brady Clark
- Sussex Research Laboratories Inc., Ottawa, ON, K1A 0R6, Canada
| | - Ian C Schoenhofen
- Human Health Therapeutics Portfolio, National Research Council Canada, Ottawa, ON, K1A 0R6, Canada.
| | - Christopher N Boddy
- Department of Chemistry and Biomolecular Sciences, Centre for Chemical and Synthetic Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada.
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Qi T, Yang HQ, Whitfield DM, Yu K, Hu CW. Insights into the Mechanistic Role of Diphenylphosphine Selenide, Diphenylphosphine, and Primary Amines in the Formation of CdSe Monomers. J Phys Chem A 2016; 120:918-31. [PMID: 26745558 DOI: 10.1021/acs.jpca.5b10675] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The formation mechanism of CdSe monomers from the reaction of cadmium oleate (Cd(OA)2) and SePPh2H in the presence of HPPh2 and RNH2 was studied systematically at the M06//B3LYP/6-31++G(d,p),SDD level in 1-octadecene solution. Herein, SePPh2H, HPPh2, and RNH2 act as hydrogen/proton donors with a decreased capacity, leading to the release of oleic acid (RCOOH). The longer the radius of the coordinated atom is, the larger the size of the cyclic transition state is, which lowers the activation strain and the Gibbs free energy of activation for the release of RCOOH. From the resulting RCOOCdSe-PPh2, for the formation of Ph2P-CdSe-PPh2 (G), SePPh2H acts as a catalyst, in which the turnover frequency determining transition state (TDTS) is characteristic of the Se-P bond cleavage. For the formation of RHN-CdSe-PPh2 (H), SePPh2H also serves as a catalyst, in which the TDTS is representative of the N-H bond cleavage. For the formation of Ph2PSe-CdSe-NHR (I), HPPh2 behaves as a catalyst, in which the TDTS is typical of the Se-P and N-H bond cleavage. The rate constants increase as kI < kH < kG, which is in good agreement with our previous experimental observations reported. The present study brings insight into the use of additives such as HPPh2 and RNH2 to synthesize colloidal quantum dots.
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Affiliation(s)
- Ting Qi
- College of Chemical Engineering, ‡Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, and §College of Physics, Sichuan University , Chengdu, Sichuan 610064, People's Republic of China
| | - Hua-Qing Yang
- College of Chemical Engineering, ‡Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, and §College of Physics, Sichuan University , Chengdu, Sichuan 610064, People's Republic of China
| | - Dennis M Whitfield
- College of Chemical Engineering, ‡Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, and §College of Physics, Sichuan University , Chengdu, Sichuan 610064, People's Republic of China
| | - Kui Yu
- College of Chemical Engineering, ‡Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, and §College of Physics, Sichuan University , Chengdu, Sichuan 610064, People's Republic of China
| | - Chang-Wei Hu
- College of Chemical Engineering, ‡Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, and §College of Physics, Sichuan University , Chengdu, Sichuan 610064, People's Republic of China
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Gulati S, Schoenhofen IC, Whitfield DM, Cox AD, Li J, St. Michael F, Vinogradov EV, Stupak J, Zheng B, Ohnishi M, Unemo M, Lewis LA, Taylor RE, Landig CS, Diaz S, Reed GW, Varki A, Rice PA, Ram S. Utilizing CMP-Sialic Acid Analogs to Unravel Neisseria gonorrhoeae Lipooligosaccharide-Mediated Complement Resistance and Design Novel Therapeutics. PLoS Pathog 2015; 11:e1005290. [PMID: 26630657 PMCID: PMC4668040 DOI: 10.1371/journal.ppat.1005290] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 10/30/2015] [Indexed: 01/15/2023] Open
Abstract
Neisseria gonorrhoeae deploys a novel immune evasion strategy wherein the lacto-N-neotetraose (LNnT) structure of lipooligosaccharide (LOS) is capped by the bacterial sialyltransferase, using host cytidine-5’-monophosphate (CMP)-activated forms of the nine-carbon nonulosonate (NulO) sugar N-acetyl-neuraminic acid (Neu5Ac), a sialic acid (Sia) abundant in humans. This allows evasion of complement-mediated killing by recruiting factor H (FH), an inhibitor of the alternative complement pathway, and by limiting classical pathway activation (“serum-resistance”). We utilized CMP salts of six additional natural or synthetic NulOs, Neu5Gc, Neu5Gc8Me, Neu5Ac9Ac, Neu5Ac9Az, legionaminic acid (Leg5Ac7Ac) and pseudaminic acid (Pse5Ac7Ac), to define structural requirements of Sia-mediated serum-resistance. While all NulOs except Pse5Ac7Ac were incorporated into the LNnT-LOS, only Neu5Gc incorporation yielded high-level serum-resistance and FH binding that was comparable to Neu5Ac, whereas Neu5Ac9Az and Leg5Ac7Ac incorporation left bacteria fully serum-sensitive and did not enhance FH binding. Neu5Ac9Ac and Neu5Gc8Me rendered bacteria resistant only to low serum concentrations. While serum-resistance mediated by Neu5Ac was associated with classical pathway inhibition (decreased IgG binding and C4 deposition), Leg5Ac7Ac and Neu5Ac9Az incorporation did not inhibit the classical pathway. Remarkably, CMP-Neu5Ac9Az and CMP-Leg5Ac7Ac each prevented serum-resistance despite a 100-fold molar excess of CMP-Neu5Ac in growth media. The concomitant presence of Leg5Ac7Ac and Neu5Ac on LOS resulted in uninhibited classical pathway activation. Surprisingly, despite near-maximal FH binding in this instance, the alternative pathway was not regulated and factor Bb remained associated with bacteria. Intravaginal administration of CMP-Leg5Ac7Ac to BALB/c mice infected with gonorrhea (including a multidrug-resistant isolate) reduced clearance times and infection burden. Bacteria recovered from CMP-Leg5Ac7Ac-treated mice were sensitive to human complement ex vivo, simulating in vitro findings. These data reveal critical roles for the Sia exocyclic side-chain in gonococcal serum-resistance. Such CMP-NulO analogs may provide a novel therapeutic strategy against the global threat of multidrug-resistant gonorrhea. Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection gonorrhea, has developed widespread resistance to almost every conventional antibiotic currently in clinical use. Novel therapeutics are urgently needed against this pathogen. Gonococci have the capacity to scavenge CMP-N-acetyl-neuraminic acid (CMP-Neu5Ac, a CMP-activated 9-carbon sugar that is a member of the ‘sialic acid family’) from the host to ‘cap’ its lipooligosaccharide with Neu5Ac, which renders gonococci resistant to complement, a key arm of innate immune defenses. Here, we show that gonococci also utilize derivatives (or analogs) of CMP-Neu5Ac, which not only fail to render the bacteria resistant to complement, but also prevent complement inhibition mediated by the ‘physiologic’ human sialic acid donor, CMP-Neu5Ac. When administered intravaginally to mice, a representative analog significantly shortened the duration and burden of gonococcal infection. Thus, CMP-sialic acid analogs may represent promising preventive or therapeutic agents against multidrug-resistant gonorrhea that poses a global threat to public health.
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Affiliation(s)
- Sunita Gulati
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Ian C. Schoenhofen
- Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario, Canada
- * E-mail: (ICS); (SR)
| | - Dennis M. Whitfield
- Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Andrew D. Cox
- Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario, Canada
| | | | - Frank St. Michael
- Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Evgeny V. Vinogradov
- Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Jacek Stupak
- Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario, Canada
| | - Bo Zheng
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | | | - Magnus Unemo
- WHO Collaborating Centre for Gonorrhoea and Other STIs, Department of Laboratory Medicine, Microbiology, Örebro University Hospital, Örebro, Sweden
| | - Lisa A. Lewis
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Rachel E. Taylor
- Biomedical Sciences Graduate Program, Departments of Medicine and Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, California, United States of America
| | - Corinna S. Landig
- Biomedical Sciences Graduate Program, Departments of Medicine and Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, California, United States of America
| | - Sandra Diaz
- Biomedical Sciences Graduate Program, Departments of Medicine and Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, California, United States of America
| | - George W. Reed
- Preventive and Behavioral Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Ajit Varki
- Biomedical Sciences Graduate Program, Departments of Medicine and Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, California, United States of America
| | - Peter A. Rice
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Sanjay Ram
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail: (ICS); (SR)
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Whitfield DM. In a glycosylation reaction how does a hydroxylic nucleophile find the activated anomeric carbon? Carbohydr Res 2014; 403:69-89. [PMID: 24962244 DOI: 10.1016/j.carres.2014.05.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Revised: 05/26/2014] [Accepted: 05/27/2014] [Indexed: 12/23/2022]
Abstract
The mechanism by which nucleophilic hydroxyls are attracted to activated glycopyranosyl donors is not known. Besides the intrinsic attraction of oxygen centred negative dipoles towards the developing electron deficiency at the anomeric carbon only a few suggestions have been given in the literature. By studying the effect on Density Functional Theory (DFT) modelled glycosylation reactions on the presence of polar additives as tested with acetonitrile two possible effects have been identified. One was noted in a previous publication (Carbohydr. Res.2012, 356, 180-190) and two further examples discovered here that suggest that a lone pair of a nucleophile approaching a donor with a β-leaving group from the α-face can act as the antiperiplanar lone pair that assists leaving group departure. This interaction starts at just under a nucleophile C-1 separation of 3Å and has an incipient bond angle of O-5-C-1-Nuc(O or N) of very close to 90° which can be at C-1 with the p-type orbital at C-1-O-5 of the incipient oxacarbenium ion, that is, the LUMO of the activated donor. The 2nd interaction is less well studied and is suggested to be a similar bonding interaction which moves β-face nucleophiles to O-Nuc-C-1-leaving groups angles close to 180°.
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Affiliation(s)
- Dennis M Whitfield
- National Research Council, Human Health Therapeutics, 100 Sussex Drive, Ottawa, ON K1A 0R6, Canada.
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Yu K, Liu X, Chen QY, Yang H, Yang M, Wang X, Wang X, Cao H, Whitfield DM, Hu C, Tao Y. Mechanistic Study of the Role of Primary Amines in Precursor Conversions to Semiconductor Nanocrystals at Low Temperature. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201403714] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Yu K, Liu X, Chen QY, Yang H, Yang M, Wang X, Wang X, Cao H, Whitfield DM, Hu C, Tao Y. Mechanistic Study of the Role of Primary Amines in Precursor Conversions to Semiconductor Nanocrystals at Low Temperature. Angew Chem Int Ed Engl 2014; 53:6898-904. [DOI: 10.1002/anie.201403714] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Indexed: 11/08/2022]
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Yu K, Ng P, Ouyang J, Zaman MB, Abulrob A, Baral TN, Fatehi D, Jakubek ZJ, Kingston D, Wu X, Liu X, Hebert C, Leek DM, Whitfield DM. Low-temperature approach to highly emissive copper indium sulfide colloidal nanocrystals and their bioimaging applications. ACS Appl Mater Interfaces 2013; 5:2870-2880. [PMID: 23486927 DOI: 10.1021/am302951k] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report our newly developed low-temperature synthesis of colloidal photoluminescent (PL) CuInS2 nanocrystals (NCs) and their in vitro and in vivo imaging applications. With diphenylphosphine sulphide (SDPP) as a S precursor made from elemental S and diphenylphosphine, this is a noninjection based approach in 1-dodecanethiol (DDT) with excellent synthetic reproducibility and large-scale capability. For a typical synthesis with copper iodide (CuI) as a Cu source and indium acetate (In(OAc)3) as an In source, the growth temperature was as low as 160 °C and the feed molar ratios were 1Cu-to-1In-to-4S. Amazingly, the resulting CuInS2 NCs in toluene exhibit quantum yield (QY) of ~23% with photoemission peaking at ~760 nm and full width at half maximum (FWHM) of ~140 nm. With a mean size of ~3.4 nm (measured from the vertices to the bases of the pyramids), they are pyramidal in shape with a crystal structure of tetragonal chalcopyrite. In situ (31)P NMR (monitored from 30 °C to 100 °C) and in situ absorption at 80 °C suggested that the Cu precursor should be less reactive toward SDPP than the In precursor. For our in vitro and in vivo imaging applications, CuInS2/ZnS core-shell QDs were synthesized; afterwards, dihydrolipoic acid (DHLA) or 11-mercaptoundecanoic acid (MUA) were used for ligand exchange and then bio-conjugation was performed. Two single-domain antibodies (sdAbs) were used. One was 2A3 for in vitro imaging of BxPC3 pancreatic cancer cells. The other was EG2 for in vivo imaging of a Glioblastoma U87MG brain tumour model. The bioimaging data illustrate that the CuInS2 NCs from our SDPP-based low-temperature noninjection approach are good quality.
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Affiliation(s)
- Kui Yu
- Emerging Technologies, National Research Council of Canada, Ottawa, Ontario, K1A 0R6, Canada.
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Whitfield DM. Plausible transition states for glycosylation reactions. Carbohydr Res 2012; 356:180-90. [DOI: 10.1016/j.carres.2012.03.040] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Revised: 03/27/2012] [Accepted: 03/30/2012] [Indexed: 11/29/2022]
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Kumar R, Whitfield DM. Could Diastereoselectivity in the Presence of O-2 Chiral Nonparticipating Groups Be an Indicator of Glycopyranosyl Oxacarbenium Ions in Glycosylation Reactions? J Org Chem 2012; 77:3724-39. [DOI: 10.1021/jo202563f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Rishi Kumar
- National Research Council, Institute for Biological Sciences, 100 Sussex Drive, Ottawa, Ontario,
Canada K1A 0R6
| | - Dennis M. Whitfield
- National Research Council, Institute for Biological Sciences, 100 Sussex Drive, Ottawa, Ontario,
Canada K1A 0R6
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Dicaire CJ, Yu SH, Whitfield DM, Sprott GD. Isopranoid- and dipalmitoyl-aminophospholipid adjuvants impact differently on longevity of CTL immune responses. J Liposome Res 2010; 20:304-14. [PMID: 20148707 DOI: 10.3109/08982100903544151] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The success of lipid membranes as cytotoxic T-cell (CTL) adjuvants requires targeted uptake by antigen-presenting cells (APCs) and delivery of the antigen cargo to the cytosol for processing. To target the phosphatidylserine (PS) receptor of APCs, we prepared antigen-loaded liposomes containing dipalmitoylphosphatidylserine and archaeal lipid liposomes (archaeosomes), containing an equivalent amount of archaetidylserine, and compared their ability to promote short and long-term CTL activity in animals. CTL responses were enhanced by the incorporation of PS into phosphatidylcholine/cholesterol liposomes and, to a lesser extent, into phosphatidylglycerol/cholesterol liposomes, that correlated to the amount of surface amino groups reactive with trinitrobenzoyl sulfonate. Archaeosomes contrasted to the liposome adjuvants by exhibiting higher amounts of surface amino groups and inducing superior shorter and, especially, longer-term CTL responses. The incorporation of dipalmitoyl lipids into archaeosomes induced instability and prevented long-term, but not short-term, CTL responses in mice. The importance of glycero-lipid cores (isopranoid versus dipalmitoyl) to the longevity of the CTL response achieved was shown further by incorporating dipalmitoyl phosphatidylethanolamine (DPPE) or equivalent amounts of synthetic archaetidylethanolamine (AE) into archaeosome adjuvants. Both DPPE and AE at equivalent (5 mol%) concentrations enhanced the rapidity of CTL responses in mice, indicating the importance of the head group in the short term. In the longer term, 5% of DPPE (but not 5% of AE) was detrimental. In addition to head-group effects critical to the potency of short-term CTL responses, the longer term CTL adjuvant properties of archaeosomes may be ascribed to stability imparted by the archaeal isopranoid core lipids.
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Affiliation(s)
- Chantal J Dicaire
- National Research Council, Institute for Biological Sciences, Ottawa, Ontario, Canada
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Schoenhofen IC, Vinogradov E, Whitfield DM, Brisson JR, Logan SM. The CMP-legionaminic acid pathway in Campylobacter: biosynthesis involving novel GDP-linked precursors. Glycobiology 2009; 19:715-25. [PMID: 19282391 DOI: 10.1093/glycob/cwp039] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The sialic acid-like sugar 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto-nonulosonic acid, or legion-aminic acid, is found as a virulence-associated cell-surface glycoconjugate in the Gram-negative bacteria Legionella pneumophila and Campylobacter coli. L. pneumophila serogroup 1 strains, causative agents of Legionnaire's disease, contain an alpha2,4-linked homopolymer of legionaminic acid within their lipopolysaccharide O-chains, whereas the gastrointestinal pathogen C. coli modifies its flagellin with this monosaccharide via O-linkage. In this work, we have purified and biochemically characterized 11 candidate biosynthetic enzymes from Campylobacter jejuni, thereby fully reconstituting the biosynthesis of legionaminic acid and its CMP-activated form, starting from fructose-6-P. This pathway involves unique GDP-linked intermediates, likely providing a cellular mechanism for differentiating between this and similar UDP-linked pathways, such as UDP-2,4-diacetamido-bacillosamine biosynthesis involved in N-linked protein glycosylation. Importantly, these findings provide a facile method for efficient large-scale synthesis of legionaminic acid, and since legionaminic acid and sialic acid share the same D-glycero-D-galacto absolute configuration, this sugar may now be evaluated for its potential as a sialic acid mimic.
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Affiliation(s)
- Ian C Schoenhofen
- Institute for Biological Sciences, National Research Council, Ottawa, Ontario, K1A 0R6 Canada.
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16
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McNally DJ, Schoenhofen IC, Houliston RS, Khieu NH, Whitfield DM, Logan SM, Jarrell HC, Brisson JR. CMP-pseudaminic acid is a natural potent inhibitor of PseB, the first enzyme of the pseudaminic acid pathway in Campylobacter jejuni and Helicobacter pylori. ChemMedChem 2008; 3:55-9. [PMID: 17893902 DOI: 10.1002/cmdc.200700170] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- David J McNally
- National Research Council of Canada-Institute for Biological Sciences, Ottawa ON, K1A 0R6, Canada.
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17
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Sprott GD, Dicaire CJ, Côté JP, Whitfield DM. Adjuvant potential of archaeal synthetic glycolipid mimetics critically depends on the glyco head group structure. Glycobiology 2008; 18:559-65. [DOI: 10.1093/glycob/cwn038] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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18
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Ionescu AR, Whitfield DM, Zgierski MZ. O-2 Substituted pyranosyl oxacarbenium ions are C-2–O-2 2-fold rotors with a strong syn preference. Carbohydr Res 2007; 342:2793-800. [DOI: 10.1016/j.carres.2007.09.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 09/14/2007] [Accepted: 09/20/2007] [Indexed: 10/22/2022]
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19
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Whitfield DM, Nukada T. DFT studies of the role of C-2–O-2 bond rotation in neighboring-group glycosylation reactions. Carbohydr Res 2007; 342:1291-304. [DOI: 10.1016/j.carres.2007.03.030] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 03/26/2007] [Accepted: 03/30/2007] [Indexed: 11/15/2022]
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20
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Whitfield DM. DFT studies of the ionization of alpha and beta glycopyranosyl donors. Carbohydr Res 2007; 342:1726-40. [PMID: 17555731 DOI: 10.1016/j.carres.2007.05.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 04/26/2007] [Accepted: 05/06/2007] [Indexed: 11/28/2022]
Abstract
Current attempts at mimicking the transition states (TSs) of glycosyl processing enzymes (GPEs) that proceed through TSs with a high degree of oxacarbenium ion formation suffer from a paucity of data about the conformations of such oxacarbenium ions. Because TSs are maxima, the current models based on minimized structures may need some refinement. As part of studies directed at optimizing chemical glycosylation the ionization of 3,4,6-tri-O-acetyl-alpha/beta-D-glucopyranosyl chlorides and triflates, 2,3,4,6-tetra-O-methyl-alpha/beta-D-glucopyranosyl fluorides, chlorides and triflates, 2,3,4,6-tetra-O-methyl-alpha/beta-D-mannopyranosyl fluorides, 2,3-di-O-methyl 4,6-O-benzylidene alpha/beta-D-mannopyranosyl triflates and 2,3-di-O-methyl 4,6-O-benzylidene alpha/beta-D-glucopyranosyl triflates was studied by a prototypic density functional theory (DFT) procedure. In all cases, the alpha-anomers ionized smoothly to 4H3 half chair conformations or adjacent envelopes. By contrast, all beta-anomers exhibited an abrupt conformational change before ionization was complete. The nature of the conformations sampled depends on both the leaving group and the protecting group. The methods presented can be readily adapted to the study of any GPE or chemical glycosylation and provide a method for initial evaluation of plausible TSs, which in turn can be used in mimetic design.
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Affiliation(s)
- Dennis M Whitfield
- Institute for Biological Sciences, NRC Canada, 100 Sussex Drive, Ottawa, ON, Canada K1A 0R6.
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21
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McNally DJ, Schoenhofen IC, Mulrooney EF, Whitfield DM, Vinogradov E, Lam JS, Logan SM, Brisson JR. Identification of labile UDP-ketosugars in Helicobacter pylori, Campylobacter jejuni and Pseudomonas aeruginosa: key metabolites used to make glycan virulence factors. Chembiochem 2007; 7:1865-8. [PMID: 17031886 DOI: 10.1002/cbic.200600298] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- David J McNally
- National Research Council of Canada-Institute for Biological Sciences, Ottawa ON, K1A 0R6, Canada.
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22
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Whitfield DM, Carver JP, Krepinsky JJ. Syntheses of Model Oligosaccharides of Biological Significance. VI. Glycosylation at C-3 of Galactose: A Synthesis of Trideuterio-Methyl 3-O-(-Acetamido-2-Deoxy-β-D-Glucopyranosyl)-β-D-Galactopyranoside. J Carbohydr Chem 2006. [DOI: 10.1080/07328308508070187] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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23
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Whitfield DM, Shah RN, Carver JP, Krepinsky JJ. Insoluble Promoters of O-Glycosylation Reaction: Thallium, Cobalt, and Cadmium Zeolites 4A and 13X. SYNTHETIC COMMUN 2006. [DOI: 10.1080/00397918508063866] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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24
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Ionescu AR, Whitfield DM, Zgierski MZ, Nukada T. Investigations into the role of oxacarbenium ions in glycosylation reactions by ab initio molecular dynamics. Carbohydr Res 2006; 341:2912-20. [PMID: 17069777 DOI: 10.1016/j.carres.2006.09.027] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 09/14/2006] [Accepted: 09/21/2006] [Indexed: 10/24/2022]
Abstract
We present a constrained ab initio molecular dynamics method that allows the modeling of the conformational interconversions of glycopyranosyl oxacarbenium ions. The model was successfully tested by estimating the barriers to ring inversion for two 4-substituted tetrahydropyranosyl oxacarbenium ions. The model was further extended to predict the pathways that connect the (4)H(3) half-chair conformation of 2,3,4,6-tetra-O-methyl-d-glucopyranosyl cation to its inverted (5)S(1) conformation and the (4)H(3) half-chair conformation of 2,3,4,6-tetra-O-methyl-d-mannopyranosyl cation to its inverted (3)E conformation. The modeled interconversion pathways reconcile a large body of experimental work on the acid-catalyzed hydrolysis of glycosides and the mechanisms of a number of glucosidases and mannosidases.
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Affiliation(s)
- Andrei R Ionescu
- Steacie Institute for Molecular Sciences, NRC Canada, 100 Sussex Drive, Ottawa, Ont., Canada
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25
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McNally DJ, Schoenhofen IC, Mulrooney EF, Whitfield DM, Vinogradov E, Lam JS, Logan SM, Brisson JR. Cover Picture: Identification of Labile UDP-Ketosugars in Helicobacter pylori, Campylobacter jejuni and Pseudomonas aeruginosa: Key Metabolites used to make Glycan Virulence Factors (ChemBioChem 12/2006). Chembiochem 2006. [DOI: 10.1002/cbic.200690036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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26
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Gerbst AG, Ustuzhanina NE, Grachev AA, Khatuntseva EA, Tsvetkov DE, Whitfield DM, Berces A, Nifantiev NE. SYNTHESIS, NMR, AND CONFORMATIONAL STUDIES OF FUCOIDAN FRAGMENTS. III. EFFECT OF BENZOYL GROUP AT O-3 ON STEREOSELECTIVITY OF GLYCOSYLATION BY 3-O- AND 3,4-DI-O-BENZOYLATED 2-O-BENZYLFUCOSYL BROMIDES. J Carbohydr Chem 2006. [DOI: 10.1081/car-100108659] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Alexey G. Gerbst
- a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Leninsky prospect 47, Moscow B-334, 119991, Russia
| | - Nadezhda E. Ustuzhanina
- a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Leninsky prospect 47, Moscow B-334, 119991, Russia
| | - Alexey A. Grachev
- b Russian Academy of Sciences , Higher Chemical College , Moscow, Russian Federation
| | - Elena A. Khatuntseva
- a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Leninsky prospect 47, Moscow B-334, 119991, Russia
| | - Dmitry E. Tsvetkov
- a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Leninsky prospect 47, Moscow B-334, 119991, Russia
| | - Dennis M. Whitfield
- c National Research Council of Canada , 100 Sussex Drive, Ottawa, ON, K1A, OR6, Canada
| | - Attila Berces
- c National Research Council of Canada , 100 Sussex Drive, Ottawa, ON, K1A, OR6, Canada
| | - Nikolay E. Nifantiev
- a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences , Leninsky prospect 47, Moscow B-334, 119991, Russia
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McNally DJ, Jarrell HC, Khieu NH, Li J, Vinogradov E, Whitfield DM, Szymanski CM, Brisson JR. The HS:19 serostrain of Campylobacter jejuni has a hyaluronic acid-type capsular polysaccharide with a nonstoichiometric sorbose branch and O-methyl phosphoramidate group. FEBS J 2006; 273:3975-89. [PMID: 16879613 DOI: 10.1111/j.1742-4658.2006.05401.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A recent study that examined multiple strains of Campylobacter jejuni reported that HS:19, a serostrain that has been associated with the onset of Guillain-Barré syndrome, had unidentified labile, capsular polysaccharide (CPS) structures. In this study, we expand on this observation by using current glyco-analytical technologies to characterize these unknown groups. Capillary electrophoresis electrospray ionization MS and NMR analysis with a cryogenically cooled probe (cold probe) of CPS purified using a gentle enzymatic method revealed a hyaluronic acid-type [-4)-beta-D-GlcA6NGro-(1-3)-beta-D-GlcNAc-(1-]n repeating unit, where NGro is 2-aminoglycerol. A labile alpha-sorbofuranose branch located at C2 of GlcA was determined to have the L configuration using a novel pyranose oxidase assay and is the first report of this sugar in a bacterial glycan. A labile O-methyl phosphoramidate group, CH3OP(O)(NH2)(OR) (MeOPN), was found at C4 of GlcNAc. Structural heterogeneity of the CPS was due to nonstoichiometric glycosylation with sorbose at C2 of GlcA and the nonstoichiometric, variably methylated phosphoramidate group. Examination of whole bacterial cells using high-resolution magic angle spinning NMR revealed that the MeOPN group is a prominent feature on the cell surface for this serostrain. These results are reminiscent of those in the 11168 and HS:1 strains and suggest that decoration of CPS with nonstoichiometric elements such as keto sugars and the phosphoramidate is a common mechanism used by this bacterium to produce a structurally complex surface glycan from a limited number of genes. The findings of this work with the HS:19 serostrain now present a means to explore the role of CPS as a virulence factor in C. jejuni.
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Affiliation(s)
- David J McNally
- Institute for Biological Sciences, National Research Council of Canada, Ottawa Ontario, Canada
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28
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lonescu A, Wang L, Zgierski MZ, Nukada T, Whitfield DM. Two Unexpected Effects Found with 2,3,4,6-Tetra-O-methyl-D-Gluco- and Mannopyranosyl Oxacarbenium Ions. ACTA ACUST UNITED AC 2006. [DOI: 10.1021/bk-2006-0930.ch017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
Affiliation(s)
- Andrei lonescu
- Steacie Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| | - LiJie Wang
- Steacie Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| | - Marek Z. Zgierski
- Steacie Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| | - Tomoo Nukada
- The Institute for Physical and Chemcial Research (RIKEN), Wako-shi, 351-01 Saitama, Japan
| | - Dennis M. Whitfield
- Institute for Biological Sciences, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
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Nukada T, Bérces A, Wang L, Zgierski MZ, Whitfield DM. The two-conformer hypothesis: 2,3,4,6-tetra-O-methyl-mannopyranosyl and -glucopyranosyl oxacarbenium ions. Carbohydr Res 2005; 340:841-52. [PMID: 15780250 DOI: 10.1016/j.carres.2004.12.021] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Accepted: 12/10/2004] [Indexed: 11/21/2022]
Abstract
Computational chemistry can give information about the probable conformations of reactive intermediates that are difficult to determine experimentally. Based on density functional theory (DFT) calculations of tetra-O-methyl-D-mannopyranosyl and -glucopyranosyl oxacarbenium ions, two families of conformations, which we call B0 and B1, were found. For the manno configuration, a 4H3 and 3E almost isoenergetic pair were found, whereas for the gluco-configuration a 4H3 and 5S1 pair favouring 4H3 were calculated. These results corroborate earlier results and suggest that this two or more conformer hypothesis is general. Nucleophilic attack on these pairs of cations was modelled with methanol and led to four cases to consider namely alpha- or beta-attack on B0 or B1. The resulting complexes (G0, G1 and F0, F1) demonstrate facial selectivity. The relative energies of these complexes are dominated by intramolecular hydrogen bonding and the conformational consequences to the pyranose ring of changes in the C-5-O-5-C-1-C-2 torsion angle. Constrained variation of the nucleophilic oxygen (methanol) to C-1 distance shows that these ion dipole complexes are the only minima with this constraint.
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Affiliation(s)
- Tomoo Nukada
- The Institute for Physical and Chemical Research (RIKEN), Wako-shi, 351-01 Saitama, Japan
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Ionescu AR, Bérces A, Zgierski MZ, Whitfield DM, Nukada T. Conformational Pathways of Saturated Six-Membered Rings. A Static and Dynamical Density Functional Study. J Phys Chem A 2005; 109:8096-105. [PMID: 16834195 DOI: 10.1021/jp052197t] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The conformation of the six-membered ring of pyranosyl sugars has pronounced effects on the physical and chemical properties of carbohydrates. We present a method to determine key features of the potential energy surfaces, such as transition states associated with the inversion pathways of the model compounds cyclohexane, tetrahydropyran, p-dioxane, m-dioxane, s-trioxane, and 2-oxanol. Finally, we make the first determination of the pathways for inversion of penta-O-methyl-alpha-D-glucopyranose and penta-O-methyl-beta-D-glucopyranose. For both anomers, a transition state with five coplanar atoms with appreciable (O)E character was found. The method is based on constrained Car-Parrinello ab initio molecular dynamics, as implemented in the projector augmented-wave (PAW) method. The constraints are derived from the normal modes of six-membered rings and are described in terms of the canonical conformations (1)C(4) chair, (1,4)B boat, and (O)S(2) skew-boat. The PAW derived trajectories are in agreement with previous suggestions in the literature that pseudorotation is an important feature of such conformational interconversions. The dynamic nature as well as the internal coordinate-based constraints provide a method which can reliably accommodate pseudorotation. To determine semiquantitative energies, we recalculate key conformations using standard quantum mechanical calculations while keeping the ring dihedral angles frozen at their values found in the dynamics. In all cases where experimental barriers are known, our results are in excellent agreement.
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Affiliation(s)
- Andrei R Ionescu
- Steacie Institute for Molecular Sciences, National Research Council of Canada, Theory and Computation Program, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
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31
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Ke W, Whitfield DM, Brisson JR, Enright G, Jarrell HC, Wu WG. Development of specific inhibitors for heparin-binding proteins based on the cobra cardiotoxin structure: an effective synthetic strategy for rationally modified heparin-like disaccharides and a trisaccharide. Carbohydr Res 2005; 340:355-72. [PMID: 15680590 DOI: 10.1016/j.carres.2004.11.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2004] [Accepted: 11/30/2004] [Indexed: 11/23/2022]
Abstract
Recently, a new heparin disaccharide-binding site on the convex side of cobra cardiotoxin (CTX) was identified by NMR spectroscopy and molecular modeling. To further characterize this site two heparin-like disaccharides were synthesized for binding studies with CTX, and a trisaccharide was synthesized for testing the sequence of the disaccharide binding to CTX. Thus six differentially protected monosaccharide building blocks (three l-iduronic acids and three d-glucosamines) were prepared. These include a l-iduronic acid elongation building block namely methyl 2-O-acetyl-4-O-levulinoyl-3-O-pivaloyl-alpha-l-idopyranosyluronate trichloroacetimidate for which a single-crystal X-ray structure was determined to have M(r)=576.79, a=9.3098(11)A alpha=90 degrees , b=10.3967(12)A beta=90 degrees , c=28.026(3)A gamma=90 degrees , V=2712.7(6)A(3), P2(1)2(1)2(1), Z=4, mu=0.71073A, and R=0.0378 for 7586 observed reflections. It shows that the molecular structure of the donor is in the (1)C(4) conformation with significant 1,3-diaxial interactions between O-1 and O-3 as well as O-2 and O-4. The disaccharides and trisaccharide vary in the degree and position of O- and N-sulfation. The pivaloyl group was used as permanent protecting group of hydroxyl. The levulinoyl group was used as the temporary protecting group to protect the hydroxyl for elongation.
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Affiliation(s)
- Weijun Ke
- Institute for Biological Sciences, National Research Council, Ottawa, ON, Canada K1A 0R6
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Ke W, Whitfield DM. A selective Sc(OTf)3-catalyzed trialkylsilyl ether to acetyl ester exchange reaction with β-l-idopyranoside and 3,4-O-isopropylidene-β-d-galactopyranoside derivatives. Carbohydr Res 2004; 339:2841-50. [PMID: 15582610 DOI: 10.1016/j.carres.2004.10.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2004] [Accepted: 10/11/2004] [Indexed: 11/27/2022]
Abstract
The selective silylation of monosaccharide building blocks is useful for preparing complex oligosaccharides. We now report that the diol, methyl (dimethylthexylsilyl 3-O-pivaloyl-beta-L-idopyranosyl)uronate, can be selectively silylated at the O-2 position by trialkylsilyl triflates. After protection of O-4, the O-2 silyl group can be selectively replaced by acetate by taking advantage of a trialkylsilyl-acetate exchange reaction catalyzed by Sc(OTf)3 in the presence of acetic anhydride. The high O-2 selectivity is shown for triethylsilyl (TES), tert-butyldimethylsilyl (TBS), and triisopropylsilyl (TIPS). The selective cleavage reaction only worked well for TES and TBS derivatives. A selection of silyl triflates and silyl chlorides were used as silylating reagents with ethyl 3,4-O-isopropylidene-1-thio-beta-D-galactopyranoside. In most cases, silylation afforded 2,6-di-O-silylated products in high yields. Studies on the cleavage reaction showed that only the primary silylated protecting groups were replaced by acetyl groups. This reaction worked with a variety of silyl protecting groups but not the tert-butyldiphenylsilyl (TBDPS) protecting group. Unfortunately, the 1-thioethyl group was also sensitive to the Sc(OTf)3, leading in these conditions to alpha/beta mixtures of the 1-acetates, which compromised the synthetic utility of this reaction for these compounds. The sequence presented here is a useful synthetic route to differentially protected L-iduronic acid building blocks.
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Affiliation(s)
- Weijun Ke
- Institute for Biological Sciences, National Research Council, Ottawa, Canada ON K1A 0R6
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Bérces A, Whitfield DM, Nukada T, do Santos Z. I, Obuchowska A, Krepinsky JJ. Is acyl migration to the aglycon avoidable in 2-acyl assisted glycosylation reactions? CAN J CHEM 2004. [DOI: 10.1139/v04-059] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This report unequivocally separates orthoester formation from acyl transfer for the first time and indicates possible routes to eliminate 2-O-acyl transfer during glycosylation reactions. Experimental evidence is shown that acyl transfer from 2-O-acyl-3,4,6-tri-O-benzyl-D-galactopyranose-derived glycosyl donors decreases in the order formyl > acetyl > pivaloyl. The 2-O-benzoyl derivatives are more variable, in some cases transferring easily, and in others not at all. Density functional theory (DFT) calculations of the structure and energetics of dioxolenium ion and related intermediates suggest that a proton transfer pathway from the nucleophile to O-2 provides an explanation for the observed trends. These DFT calculations of the proton transfer pathway support a mechanism in which a relay molecule is involved. Further DFT calculations used a constraint based on linear combinations of six bond lengths to establish the sequence of bond breaking and bond forming. The calculated anomeric carbon to former carbonyl oxygen bond that breaks during acyl transfer is the longest in the formyl case and shortest in those that exhibit little or no acyl transfer. Rotation about the aromatic to carbonyl PhC(=O) bond is different from the alkyl series. Analysis of this proposed TS led to the postulate that 2,6-substitution may hinder rotation even more. Thus, the 2,6-dimethylbenzoyl analogue was synthesized and it does not transfer directly or by rearrangement of its readily formed orthoester. DFT calculations suggested that 2,6-dimethoxybenzoyl should also not transfer easily. Experimentally, this proved to be the case and this new 2-O-acyl protecting group cleaves at 50 °C with a 1 mol/L solution of LiOH in methanol. Thus, a calculated transition state has led to a prototype of a protecting group that solves a major problem in oligosaccharide synthesis.Key words: glycosylation, carbohydrates, quantum chemistry, reaction mechanism, neighboring-group effects.
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34
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Yan F, Mehta S, Eichler E, Wakarchuk WW, Gilbert M, Schur MJ, Whitfield DM. Simplifying oligosaccharide synthesis: efficient synthesis of lactosamine and siaylated lactosamine oligosaccharide donors. J Org Chem 2003; 68:2426-31. [PMID: 12636412 DOI: 10.1021/jo026569v] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A practical sequence is described for converting d-glucosamine into peracetylated Gal(beta-1,4)GlcNTroc(beta1-S)Ph and Neu5Ac(alpha-2,3)Gal(beta-1,4)GlcNTroc(beta1-S)Ph building blocks using a synthetic strategy based on chemoenzymatic oligosaccharide synthesis. The known trichloroethoxycarbonyl, N-Troc, protecting group was selected as a suitable protecting group for both enzymatic and chemical reaction conditions. These oligosaccharide building blocks proved effective donors for the beta-selective glycosylation of the unreactive OH-3 of a polymeric PEG-bound acceptor and for the axial OH-2 of a mannose acceptor in good yields. The resulting complex oligosaccharides are useful for vaccine and pharmaceutical applications.
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Affiliation(s)
- Fengyang Yan
- Institute for Biological Sciences, National Research Council of Canada, 100 Sussex Drive, Room 3024, Ottawa, Ontario, K1A 0R6, Canada
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Douglas SP, Whitfield DM, Krepinsky JJ. Polymer-Supported Solution Synthesis of Oligosaccharides Using a Novel Versatile Linker for the Synthesis of D-Mannopentaose, a Structural Unit of D-Mannans of Pathogenic Yeasts. J Am Chem Soc 2002. [DOI: 10.1021/ja00112a035] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Whitfield DM, Tang TH. Binding properties of carbohydrate O-sulfate esters based on ab initio 6-31 +G** calculations on methyl and ethyl sulfate anions. J Am Chem Soc 2002. [DOI: 10.1021/ja00074a033] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Fyles TM, McGavin CA, Whitfield DM. Synthesis of lipophilic 18-crown-6 diacids for the membrane transport of alkaline-earth cations. J Org Chem 2002. [DOI: 10.1021/jo00179a004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Nukada T, Bérces A, Whitfield DM. Can the stereochemical outcome of glycosylation reactions be controlled by the conformational preferences of the glycosyl donor? Carbohydr Res 2002; 337:765-74. [PMID: 11950473 DOI: 10.1016/s0008-6215(02)00043-5] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Previous static and dynamical density functional theory studies of the 2,6-di-O-acetyl-3,4-O-isopropylidene-D-galactopyranosyl cations and their methanol adducts has led to an hypothesis that these cations exist in two families of conformers characterized as (2)S(O) and B(2,5), respectively. These families differ by ring inversion, each with its own reactivity. New calculations on the 2,6-di-O-acetyl-3,4-di-O-methyl-D-galactopyranosyl cation confirmed these trends. Removing the isopropylidene group allows more flexibility, but two families of conformers can be discerned with the monocyclic oxocarbenium ions in the E(3) conformation and the bicyclic dioxolenium ions in the (4)H(5) conformation. Attack on the beta-face of these monocyclic cations is favored by hydrogen bonding and the anomeric effect. The experimentally observed high beta-stereoselectivity of mannopyranosyl donors and high alpha-stereoselectivity of glucopyranosyl donors with the 4,6-O-benzylidene protecting groups can be rationalized assuming that the trans-fused 1,3-dioxane ring allows population of only one family of conformers. The combination of hydrogen bonding and conformational changes of the pyranose ring in response to the C-5[bond]O-5[bond]C-1[bond]C-2 torsion angle changes are identified as key factors in stereoselectivity. Based on these observations a strategy to design face discriminated glycosyl donors that exist predominantly in only one family of conformers is proposed.
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Affiliation(s)
- Tomoo Nukada
- The Institute for Physical and Chemical Research (RIKEN), Wako-shi, 351-01 Saitama, Japan
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Yan F, Gilbert M, Wakarchuk WW, Brisson JR, Whitfield DM. Chemoenzymatic iterative synthesis of difficult linkages of oligosaccharides on soluble polymeric supports. Org Lett 2001; 3:3265-8. [PMID: 11594810 DOI: 10.1021/ol016466j] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
[reaction: see text]. A trisaccharide donor containing a cis-Galpalpha(1-->4)Galp linkage was prepared using a synthetic strategy based on chemoenzymatic oligosaccharide synthesis on a soluble polymeric support. Significantly, only retaining glycosyltransferases gave complete reactions, whereas inverting enzymes showed little or no activity with poly(ethylene glycol) (MPEG)-bound lactose as an acceptor. The MPEG-attached trisaccharide was shown to bind to Verotoxin-1 by transfer NOE studies through the Galpalpha(1-->4)Galp portion of the molecule.
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Affiliation(s)
- F Yan
- Institute for Biological Sciences, National Research Council of Canada, 100 Sussex Drive, Room 3024, Ottawa, Ontario K1A 0R6, Canada
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Bérces A, Enright G, Nukada T, Whitfield DM. The conformational origin of the barrier to the formation of neighboring group assistance in glycosylation reactions: a dynamical density functional theory study. J Am Chem Soc 2001; 123:5460-4. [PMID: 11389627 DOI: 10.1021/ja001194l] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Static and dynamical Density Functional Theory studies of 2,6-di-O-acetyl-3,4-O-isopropylidene-D-galactopyranosyl cation have shown that this cation can exist in two conformers characterized as (2)S(O) and B(2,5), respectively. The (2)S(O) conformer has the O-2 acyl group equatorial with the carbonyl syn to H-2 and is populated by monocyclic oxocarbenium ions. These conformational features are present in the structurally related glycosyl donor ethyl 2,6-di-O-benzoyl-3,4-O-isopropylidene-beta-D-galactothiopyranoside as determined by X-ray diffraction studies. The B(2,5) conformer has O-2 axial and allows the carbonyl to rotate and close the five-membered ring to form a bicyclic dioxolenium ion. Constraints based on natural internal coordinates were implemented to study this conformational transition. In this way the barrier to interconversion has been determined to be 34 kJ mol(-)(1) with a transition state characterized as (O)S(2) and a pathway involving pseudorotation. Thus, for the first time the structures and energetics of the key ions postulated to be involved in neighboring group assisted glycosylation reactions have been determined.
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Affiliation(s)
- A Bérces
- Steacie Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Dr., Ottawa, Ontario K1A 0R6, Canada
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Abstract
beta-Glucans are polysaccharides that act as nonspecific immune system stimulants. However, many beta-Glucans are sparingly soluble in water. This work describes an oxidative procedure, which solubilizes the beta-Glucan from Saccharomyces cerevisiae and maintains its immunostimulatory properties. Furthermore, the carboxylates at the site of oxidation allow for the conjugation of small molecule immunostimulants. Both the parent oxidized beta-glucan and its conjugates with O-beta-alanyl-5-[6-(N,N'-dimethylamino)purin-9-yl]pentanol stimulate cytotoxic T-lymphocytes (CTLs), B cells and macrophages. In addition, they both stimulate natural killer (NK) cells, a property which the small molecule purine does not possess.
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Affiliation(s)
- G G Cross
- National Research Council, 100 Sussex Drive, Ottawa, Ontario, Canada K1A 0R6
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Yan F, Wakarchuk WW, Gilbert M, Richards JC, Whitfield DM. Polymer-supported and chemoenzymatic synthesis of the Neisseria meningitidis pentasaccharide: a methodological comparison. Carbohydr Res 2000; 328:3-16. [PMID: 11005572 DOI: 10.1016/s0008-6215(00)00086-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neisseria meningitidis trisaccharide [GlcNAc[(1-->3)Galbeta(1-->4)Glc-R], tetrasaccharide [Galbeta(1-->4)GlcNAcbeta(1--> 3)Galbeta(1-->4)Glc-R], and a pentasaccharide [Neu5Acalpha(2-->3)Galbeta(1-->4)GlcNAcbeta(1-->3)G albeta(1-->4)Glc-SPh] were prepared via conventional chemical synthesis, polymer-supported synthesis, and chemoenzymatic methods, starting from D-lactose. The polymer polyethyleneglycol monomethylether (MPEG) and the linker dioxyxylene (DOX) were used with a lactose-bound acceptor to improve the purification process. Several enzymes (LgtA, GalE-LgtB fusion, and CMP-Neu5Ac synthetase/sialyltransferase fusion) were used for syntheses of these oligosaccharides. Excellent stereo- and regioselectivities as well as high yield (> 90% from Gal(1-->4)Glc-SPh) of the pentasaccharide were obtained. Both of the convenient processes are suitable for efficient preparation of target oligosaccharides.
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Affiliation(s)
- F Yan
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ont
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Mehta S, Whitfield DM. Polymer-Supported Synthesis of a Branched Trisaccharide of the Type IA Group B Streptococcus Capsular Polysaccharide: 3-Iodo-4-methoxybenzyl as a New O-Protecting Group. Tetrahedron 2000. [DOI: 10.1016/s0040-4020(00)00612-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
[formula: see text] Numerous glycoconjugates contain the disaccharide Neu5Ac alpha (2-->3)DGalp. An efficient way to incorporate this disaccharide into synthetic glycoconjugates is to develop a disaccharide building block. This communication reports a chemoenzymatic route to such a building block which requires as few as four steps. Some examples using more chemical steps are also presented, which increase the flexibility. These disaccharide donors were used to prepare synthetic trisaccharides.
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Affiliation(s)
- S Mehta
- National Research Council, Ottawa, Ontario, Canada
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Affiliation(s)
- Tomoo Nukada
- The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351, Japan, and National Research Council, Ottawa, Ontario K1A 0R6, Canada
| | - Attila Berces
- The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351, Japan, and National Research Council, Ottawa, Ontario K1A 0R6, Canada
| | - Dennis M. Whitfield
- The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351, Japan, and National Research Council, Ottawa, Ontario K1A 0R6, Canada
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Abstract
As part of our program to design, develop and prepare protective vaccines against the bacterial pathogens Group B Streptococcus, we report the synthesis of a disialylated hexasaccharide. This hexasaccharide represents a portion of the serotype-specific capsular polysaccharide of Type VIII that has the tetrasaccharide repeat unit [beta-L-Rhap-(1-->4)-beta-D-Glcp-(1-->4)-[alpha-Neu5Ac-(2--> 3)]-beta-D- Galp-(1-->4)]n. A tetrasaccharide corresponding to this repeat unit has been synthesized by us [E. Eichler, H.J. Jennings, D.M. Whitfield, J. Carbohydr. Chem., 16 (1997) 385-411]. Since the protective epitopes are believed to involve several repeat units, methods to extend this tetrasaccharide were examined. This objective requires a glycosylation of the unreactive OH-4 of the beta-L-Rhap, which was accomplished by coupling a D-Galp glycosyl trichloroacetimidate donor with a beta-L-Rhap-(1-->4)-D-Glcp acceptor. Subsequent coupling of this trisaccharide as a donor to an alpha-Neu5Ac-(2-->3)-D-Galp disaccharide acceptor gave a pentasaccharide. The pentasaccharide was deprotected and enzymatically sialylated using an alpha-(2-->3)-sialyltransferase from Campylobacter jejuni to give the title hexasaccahride alpha-Neu5Ac-(2-->3)- beta-D-Galp-(1-->4)-beta-L-Rhap-(1-->4)-beta-D-Glcp-(1-->4)-[alpha -Neu5Ac- (2-->3)]-beta-D-Galp-(1-->O)-(CH2)3N3.
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Affiliation(s)
- E Eichler
- National Research Council, Ottawa, Ontario, Canada
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Affiliation(s)
- Tomoo Nukada
- Contribution from The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351, Japan, and National Research Council, Ottawa, Ontario, K1A 0R6, Canada
| | - Attila Berces
- Contribution from The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351, Japan, and National Research Council, Ottawa, Ontario, K1A 0R6, Canada
| | - Marek Z. Zgierski
- Contribution from The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351, Japan, and National Research Council, Ottawa, Ontario, K1A 0R6, Canada
| | - Dennis M. Whitfield
- Contribution from The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351, Japan, and National Research Council, Ottawa, Ontario, K1A 0R6, Canada
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Abstract
It was anticipated that stannylation of carbohydrates could be achieved using tin on a polymer-support. Such immobilization simplifies the purification of the carbohydrate because the toxic tin reagent can be removed by filtration. In this case an alkene linker (3-buten-1-ol) was added to chloromethylated 2% cross-linked polystyrene by etherification. Photochemical hydrostannylation with dibutyltinchlorohydride gave a polymer bound trialkyl tin chloride. The Sn-Cl could be hydrolysed with NaOH to yield a resin with terminal Sn-O bonds. Highly regioselective acylation of methyl alpha-D-mannopyranoside (alphaMeMan) to its 3-O-benzoyl derivative was achieved. Traces of the mono 6-O-benzoate and the 3,6-di-O-benzoate were also obtained. Methyl alpha-D-glucopyranoside was also selectively acylated to its 2-O-benzoate but this reaction gave a more complex mixture. The isolated yields (10-30% based on sugar) were disappointingly low. The yields were improved to about 60% with 5% cross-linked resin.
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Eichler E, Jennings HJ, Whitfield DM. Synthesis of a Single Repeat Unit of Type VIII Group BStreptococcusCapsular Polysaccharide1. J Carbohydr Chem 1997. [DOI: 10.1080/07328309708007324] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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