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Loh ZH, Hungerford NL, Ouwerkerk D, Klieve AV, Fletcher MT. Identification of Acid Hydrolysis Metabolites of the Pimelea Toxin Simplexin for Targeted UPLC-MS/MS Analysis. Toxins (Basel) 2023; 15:551. [PMID: 37755977 PMCID: PMC10535249 DOI: 10.3390/toxins15090551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 08/23/2023] [Accepted: 08/26/2023] [Indexed: 09/28/2023] Open
Abstract
Pimelea poisoning of cattle is a unique Australian toxic condition caused by the daphnane orthoester simplexin present in native Pimelea pasture plants. Rumen microorganisms have been proposed to metabolise simplexin by enzymatic reactions, likely at the orthoester and epoxide moieties of simplexin, but a metabolic pathway has not been confirmed. This study aimed to investigate this metabolic pathway through the analysis of putative simplexin metabolites. Purified simplexin was hydrolysed with aqueous hydrochloric acid and sulfuric acid to produce target metabolites for UPLC-MS/MS analysis of fermentation fluid samples, bacterial isolate samples, and other biological samples. UPLC-MS/MS analysis identified predicted hydrolysed products from both acid hydrolysis procedures with MS breakdown of these putative products sharing high-resolution accurate mass (HRAM) fragmentation ions with simplexin. However, targeted UPLC-MS/MS analysis of the biological samples failed to detect the H2SO4 degradation products, suggesting that the rumen microorganisms were unable to produce similar simplexin degradation products at detectable levels, or that metabolites, once formed, were further metabolised. Overall, in vitro acid hydrolysis was able to hydrolyse simplexin at the orthoester and epoxide functionalities, but targeted UPLC-MS/MS analysis of biological samples did not detect any of the identified simplexin hydrolysis products.
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Affiliation(s)
- Zhi Hung Loh
- Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Health and Food Sciences Precinct, Coopers Plains, QLD 4108, Australia; (Z.H.L.); (N.L.H.); (D.O.); (A.V.K.)
| | - Natasha L. Hungerford
- Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Health and Food Sciences Precinct, Coopers Plains, QLD 4108, Australia; (Z.H.L.); (N.L.H.); (D.O.); (A.V.K.)
| | - Diane Ouwerkerk
- Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Health and Food Sciences Precinct, Coopers Plains, QLD 4108, Australia; (Z.H.L.); (N.L.H.); (D.O.); (A.V.K.)
- Agri-Science Queensland, Department of Agriculture and Fisheries (DAF), Ecosciences Precinct, Dutton Park, QLD 4102, Australia
| | - Athol V. Klieve
- Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Health and Food Sciences Precinct, Coopers Plains, QLD 4108, Australia; (Z.H.L.); (N.L.H.); (D.O.); (A.V.K.)
| | - Mary T. Fletcher
- Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Health and Food Sciences Precinct, Coopers Plains, QLD 4108, Australia; (Z.H.L.); (N.L.H.); (D.O.); (A.V.K.)
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2
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Ondari ME, Klosin J, Froese RDJ, Kruper WR, MacDonald J, Arriola DJ, Bell BM, Briggs JR, Kruper WJ. Mechanistic and Synthetic Implications of the Diol-Ritter Reaction: Unexpected Yet Reversible Pathways in the Regioselective Synthesis of Vicinal-Aminoalcohols. J Org Chem 2019; 84:4715-4722. [PMID: 30428673 DOI: 10.1021/acs.joc.8b02320] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Ritter reaction of 1,2-diolmonoesters with nitriles to 1- vic-amido-2-esters proceeds through dioxonium and nitrilium cation intermediates. To provide the basis for the reaction mechanism, novel forms of these cations were isolated, characterized, and studied by spectroscopic methods and single crystal X-ray analysis. Ground and transition state energies were determined both experimentally and theoretically. Taken together, these data suggest that the reaction proceeds via rapid formation of the dioxonium cation 9, followed by rate determining yet reversible ring opening by acetonitrile to the corresponding nitrilium cation 10 (computed Δ G⧧ = 24.7 kcal at 50 °C). Rapid, irreversible hydration of the latter affords the corresponding vic-acetamido ester. Controlled addition of H2O to the dioxonium cation 9 in acetonitrile- d3 results in near-quantitative production of deuterated acetamido ester 13a. Kinetics of this conversion (9 to 13a) are biphasic, and the slow phase is ascribed to either direct cation 9 attack by acetamide to form cation 16 via O-alkylation or by reversible ether formation. Deuterium labeling studies suggest O-alkylated cation 16 does not directly isomerize to N-alkylated cation 18; instead, it reverts to vic-amidoester 13a via the nitrilium pathway. Preliminary results indicate high regioselectivity for primary amide formation in the diol-Ritter sequence.
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Affiliation(s)
- Mark E Ondari
- Corteva Agriscience, Agriculture Division of DowDupont , 1710 Building , Midland , Michigan 48674 , United States
| | - Jerzy Klosin
- Corporate R&D , The Dow Chemical Company , 1776 Building , Midland , Michigan 48674 , United States
| | - Robert D J Froese
- Corporate R&D , The Dow Chemical Company , 1776 Building , Midland , Michigan 48674 , United States
| | - William R Kruper
- Corteva Agriscience, Agriculture Division of DowDupont , 1710 Building , Midland , Michigan 48674 , United States
| | - Jason MacDonald
- Corteva Agriscience, Agriculture Division of DowDupont , 1710 Building , Midland , Michigan 48674 , United States
| | - Dan J Arriola
- Corporate R&D , The Dow Chemical Company , 1776 Building , Midland , Michigan 48674 , United States
| | - Bruce M Bell
- Corporate R&D , The Dow Chemical Company , 1776 Building , Midland , Michigan 48674 , United States
| | - John R Briggs
- Corporate R&D , The Dow Chemical Company , 1776 Building , Midland , Michigan 48674 , United States
| | - William J Kruper
- Michigan State University St. Andrews , Midland , Michigan 48674 , United States
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3
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Pierre TS, Chiellini E. Review : Biodegradability of Synthetic Polymers Used for Medical and Pharmaceutical Applications: Part 1— Principles of Hydrolysis Mechanisms. J BIOACT COMPAT POL 2016. [DOI: 10.1177/088391158600100405] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Thomas St. Pierre
- Instituto di Chimica Generale Facolta di Engegneria University of Pisa Pisa, Italy
| | - Emo Chiellini
- Instituto di Chimica Generale Facolta di Engegneria University of Pisa Pisa, Italy
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4
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Repetto SL, Costello JF, Butts CP, Lam JKW, Ratcliffe NM. The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals. Beilstein J Org Chem 2016; 12:1467-75. [PMID: 27559399 PMCID: PMC4979634 DOI: 10.3762/bjoc.12.143] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 06/23/2016] [Indexed: 11/23/2022] Open
Abstract
A novel approach to protecting jet fuel against the effects of water contamination is predicated upon the coupling of the rapid hydrolysis reactions of lipophilic cyclic geminal ethers, with the concomitant production of a hydrophilic acyclic hydroxyester with de-icing properties (Fuel Dehydrating Icing Inhibitors - FDII). To this end, a kinetic appraisal of the hydrolysis reactions of representative geminal ethers was undertaken using a convenient surrogate for the fuel-water interface (D2O/CD3CN 1:4). We present here a library of acyclic and five/six-membered cyclic geminal ethers arranged according to their hydroxonium catalytic coefficients for hydrolysis, providing for the first time a framework for the development of FDII. A combination of (1)H NMR, labelling and computational studies was used to assess the effects that may govern the observed relative rates of hydrolyses.
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Affiliation(s)
- Sonia L Repetto
- Faculty of Applied Sciences, University of the West of England, Bristol, BS16 1QY, UK
| | - James F Costello
- Faculty of Applied Sciences, University of the West of England, Bristol, BS16 1QY, UK
| | - Craig P Butts
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK
| | | | - Norman M Ratcliffe
- Faculty of Applied Sciences, University of the West of England, Bristol, BS16 1QY, UK
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5
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Cheng J, Ji R, Gao SJ, Du FS, Li ZC. Facile Synthesis of Acid-Labile Polymers with Pendent Ortho Esters. Biomacromolecules 2011; 13:173-9. [DOI: 10.1021/bm201410c] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Jing Cheng
- Beijing National Laboratory
for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics
of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic
of China
| | - Ran Ji
- Beijing National Laboratory
for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics
of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic
of China
| | - Shi-Juan Gao
- CAS Key Laboratory
of Pathogenic
Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, People's
Republic of China
| | - Fu-Sheng Du
- Beijing National Laboratory
for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics
of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic
of China
| | - Zi-Chen Li
- Beijing National Laboratory
for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics
of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic
of China
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6
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Du FS, Huang XN, Chen GT, Lin SS, Liang D, Li ZC. Aqueous Solution Properties of the Acid-Labile Thermoresponsive Poly(meth)acrylamides with Pendent Cyclic Orthoester Groups. Macromolecules 2010. [DOI: 10.1021/ma902227g] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fu-Sheng Du
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, P. R. China
| | - Xiao-Nan Huang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, P. R. China
| | - Guang-Tao Chen
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, P. R. China
| | - Shrong-Shi Lin
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, P. R. China
| | - Dehai Liang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, P. R. China
| | - Zi-Chen Li
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, P. R. China
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7
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Stabilities and Reactivities of Carbocations. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2010. [DOI: 10.1016/s0065-3160(08)44002-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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8
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Romberg B, Hennink WE, Storm G. Sheddable coatings for long-circulating nanoparticles. Pharm Res 2007; 25:55-71. [PMID: 17551809 PMCID: PMC2190344 DOI: 10.1007/s11095-007-9348-7] [Citation(s) in RCA: 393] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Accepted: 05/14/2007] [Indexed: 11/26/2022]
Abstract
Nanoparticles, such as liposomes, polymeric micelles, lipoplexes and polyplexes are frequently studied as targeted drug carrier systems. The ability of these particles to circulate in the bloodstream for a prolonged period of time is often a prerequisite for successful targeted delivery. To achieve this, hydrophilic ‘stealth’ polymers, such as poly(ethylene glycol) (PEG), are used as coating materials. Such polymers shield the particle surface and thereby reduce opsonization by blood proteins and uptake by macrophages of the mononuclear phagocyte system. Yet, after localizing in the pathological site, nanoparticles should deliver their contents in an efficient manner to achieve a sufficient therapeutic response. The polymer coating, however, may hinder drug release and target cell interaction and can therefore be an obstacle in the realization of the therapeutic response. Attempts have been made to enhance the therapeutic efficacy of sterically stabilized nanoparticles by means of shedding, i.e. a loss of the coating after arrival at the target site. Such an ‘unmasking’ process may facilitate drug release and/or target cell interaction processes. This review presents an overview of the literature regarding different shedding strategies that have been investigated for the preparation of sterically stabilized nanoparticulates. Detach mechanisms and stimuli that have been used are described.
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Affiliation(s)
- Birgit Romberg
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
| | - Wim E. Hennink
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
| | - Gert Storm
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
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9
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Huang X, Du F, Ju R, Li Z. Novel Acid-Labile, Thermoresponsive Poly(methacrylamide)s with PendentOrtho Ester Moieties. Macromol Rapid Commun 2007. [DOI: 10.1002/marc.200600798] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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10
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11
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Ring-opening polymerization of atom-bridged and bond-bridged bicyclic ethers, acetals and orthoesters. ADVANCES IN POLYMER SCIENCE 2005. [DOI: 10.1007/3-540-10958-7_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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12
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Guthrie JP, More O'Ferrall RA, O'Donoghue AC, Waghorne WE, Zrinski I. Estimation of a pKa for Protonated Dimethoxycarbene. J PHYS ORG CHEM 2003. [DOI: 10.1002/poc.663] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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13
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Guo X, Szoka FC. Steric stabilization of fusogenic liposomes by a low-pH sensitive PEG--diortho ester--lipid conjugate. Bioconjug Chem 2001; 12:291-300. [PMID: 11312691 DOI: 10.1021/bc000110v] [Citation(s) in RCA: 184] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe the synthesis and characterization of a pH-sensitive poly(ethylene glycol)-diortho ester-distearoyl glycerol conjugate (POD). POD was prepared by a one-step synthesis, and its acid sensitivity characterized by TLC. The conjugate was found to be stable at neutral pH for greater than 3 h but degraded completely within 1 h at pH 5. Liposomes composed of 10% of POD and 90% of a fusogenic lipid, dioleoyl phosphatidylethanolamine (DOPE) were readily prepared and remained stable for up to 12 h in neutral buffer as shown by photon correlation spectrometry and a liposome contents leakage assay. However, when POD/DOPE liposomes were incubated in acidic pH as mild as 5.5, they aggregated and released most of their contents within 30 min. The kinetics of content release from POD/DOPE liposomes consisted of two phases, a lag phase, and a burst phase. The lag phase is inversely correlated with pH and the logarithm of the length of lag phase showed a linear relationship with the buffer pH. When the POD/DOPE liposomes were incubated in 75% of fetal bovine serum at 37 degrees C, they remained as stable as traditional PEG-grafted liposomes for 12 h but released 84% of the encapsulated ANTS in the following 4 h. Upon intravenous administration into mice, liposomes composed of 10% POD and 90% DOPE were cleared from circulation by a one-compartment kinetics with a half-life of about 200 min. POD is an example for the design of a novel category of pH sensitive lipids composed of a headgroup, an acid-labile diortho ester linker and a hydrophobic tail. The uniquely fast degradation kinetics of POD at pH 5-6 and its ability to stabilize liposomes in serum make the conjugate suitable for applications for triggered drug release systems targeted to mildly acidic bio-environments such as endosomes, solid tumors, and inflammatory tissues.
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Affiliation(s)
- X Guo
- Departments of Pharmaceutical Chemistry and Biopharmaceutical Sciences, University of California at San Francisco, San Francisco, California 94143-0446, USA
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15
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Baldyga J, Bourne JR, Walker B. Non-isothermal micromixing in turbulent liquids: Theory and experiment. CAN J CHEM ENG 1998. [DOI: 10.1002/cjce.5450760336] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Buckley N, Oppenheimer NJ. Reactions of Charged Substrates. 7. The Methoxymethyl Carbenium Ion Problem. 2. A Semiempirical Study of the Kinetic and Thermodynamic Stabilities of Linear and Cyclic Oxo- and Thiocarbenium Ions Generated from Aldehyde Hydrates, Hemiacetals, Acetals, and Methyl Ribosides and Glucosides. J Org Chem 1996; 61:8048-8062. [PMID: 11667788 DOI: 10.1021/jo960748t] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Factors affecting the cleavage of the carbon-oxygen bond in linear and cyclic aldehyde hydrates, heimacetals, acetals, and methyl ribosides and glucosides have been investigated using semiempirical calculations (AM1 and PM3). (For some systems, low- and high-level ab initio energies are available for comparison with the semiempirical results. With one exception, the results obtained by the two methods show excellent agreement in relative energies and trends in reactivity.) The effects on reactivity and stability caused by substituting a sulfur for the alpha oxygen in the oxocarbenium ion were also studied. In general, systems that can have an antiperiplanar alignment of lone pairs on the leaving group and potential oxocarbenium ion oxygens undergo spontanteous cleavage. An examination of various conformers of the leaving group relative to the potential oxocarbenium oxygen shows, however, that lone pair repulsion and steric factors for MeOH as the leaving group are more important than the antiperiplanar effect for bond cleavage. All compounds in which the alpha-oxygen in the potential carbenium ion is replaced by sulfur undergo spontaneous cleavage regardless of the leaving group or structure of the compound. Energy profiles, DeltaH(), and DeltaH(R) values show that linear and cyclic thiocarbenium ions are much more stable than the corresponding oxocarbenium ions. Comparison of results for methyl ribosides and glucosides with results for corresponding pyridinium substrates suggests that both should hydrolyze through an A-1 mechanism. General-acid catalysis with hydronium as the acid was studied. With solution results, the computations suggest that substrates with either a good leaving group or stable oxocarbenium ion react with rate-limiting proton transfer from the acid to the leaving group but that substrates with both a good leaving group and stable carbenium ion react with concerted proton transfer and bond cleavage.
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Affiliation(s)
- Neil Buckley
- The Department of Pharmaceutical Chemistry, S-926, Box 0446, The University of California, San Francisco, California 94143-0446
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17
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Graczyk PP, Mikolajczyk M. Inapplicability of the Antiperiplanar Lone Pair Hypothesis to C-P Bond Breaking and Formation in Some S-C-P(+) Systems. J Org Chem 1996; 61:2995-3002. [PMID: 11667160 DOI: 10.1021/jo941771m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Both C(2)-P bond breaking and formation in the S-C-P(+) system do not occur according to the antiperiplanar lone pair hypothesis. Experiments using 2-phosphonio derivatives of 5-tert-butyl-1,3-dithiane and cis-4,6-dimethyl-1,3-dithiane are against the participation of higher-energy boat conformers as reactive intermediates. The results obtained support a possibility of conformational adjustment in the course of the reaction. Stereoelectronic control of the C(2)-P bond breaking and formation results from interplay of several factors. The role of the n(S)-sigma(C(2))(-)(P) and sigma(C(4,6))(-)(S)-sigma(C(2))(-)(P) hyperconjugation, as well as of the repulsive interactions between lone electron pairs pi(S) of endocyclic sulfur atoms and pi-electrons of the phenyl ring(s) connected with phosphorus, is discussed.
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Affiliation(s)
- Piotr P. Graczyk
- Center of Molecular and Macromolecular Studies, Polish Academy of Science, Department of Organic Sulfur Compounds, Lodz, Sienkiewicza 112, PL-90-363, Poland
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18
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Stoelting DT, Ludwig RT, Arnett EM. 2-aryl-1,3-dithianes and -dithiolanes: A nearly ideal series for relating the energies for bond breaking to electron transfer. HETEROATOM CHEMISTRY 1996. [DOI: 10.1002/(sici)1098-1071(199611)7:6<481::aid-hc11>3.0.co;2-m] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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19
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Arnett EM, Flowers RA, Meekhof AE, Pourjavadi A, Walek SA. Stabilities of some 2-(para-substituted-phenyl)-4,4,5,5-tetramethyl-1,3-dioxolanes relative to their conjugate dioxolenium ions, radicals and carbanions as determined by thermodynamics for hydride and electron transfer in solution. J PHYS ORG CHEM 1994. [DOI: 10.1002/poc.610071204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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20
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Ali M, Satchell DPN, Le VT. Kinetics of hydrolysis of 2-aryl-2-phenyl-1,3-dithianes in 10%(v/v) dioxane–water, containing perchloric acid. Acidity functions in this solvent and the reactivity of α-thio carbocations. ACTA ACUST UNITED AC 1993. [DOI: 10.1039/p29930000917] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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21
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Tue Huu Nguyen, Takeru H, Himmelstein KJ. Erosion characteristics of catalyzed poly(ortho ester) matrices. J Control Release 1987. [DOI: 10.1016/0168-3659(87)90032-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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22
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23
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Nguyen TH, Himmelstein KJ, Higuchi T. Erosion of poly(ortho ester) matrices in buffered aqueous solutions. J Control Release 1986. [DOI: 10.1016/0168-3659(86)90028-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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24
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25
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The Spectroscopic Detection of Tetrahedral Intermediates Derived from Carboxylic Acids and the Investigation of Their Properties. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 1985. [DOI: 10.1016/s0065-3160(08)60098-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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26
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Nguyen TH, Shih C, Himmelstein KJ, Higuchi T. Hydrolysis of some poly(ortho-ester)s in homogeneous solutions. J Pharm Sci 1984; 73:1563-8. [PMID: 6520759 DOI: 10.1002/jps.2600731119] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The hydrolysis of poly(ortho-ester)s and a monomeric model compound, 3,9-dibenzyloxy-3,9-diethyl-2,4,8,10-tetraoxaspiro[5,5]un decane, was carried out in dioxane-d8-dioxane and followed by 1H-NMR and HPLC, respectively. Experimental results suggested that the polymer degradation proceeds to a large extent via random scission. The hydrolysis was catalyzed by the acid; the catalytic rate constant increased predictably with decreasing aqueous pKa of the acid. The reaction is first order with respect to the catalyst concentration and the number of ortho-ester linkages present, and it is independent of water in the concentration range studied. Strain at the ortho-ester bond may be a factor influencing the hydrolysis rate.
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Shih C, Higuchi T, Himmelstein KJ. Drug delivery from catalysed erodible polymeric matrices of poly(ortho ester)s. Biomaterials 1984; 5:237-40. [PMID: 6487705 DOI: 10.1016/0142-9612(84)90022-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The incorporation of small amounts of acid anhydrides into hydrophobic poly(ortho ester)s can facilitate the erosion and drug release from delivery systems. Since the reaction can be controlled by the amount of anhydride employed, the reaction is confined to a small reaction zone near the surface and constant delivery rates can be achieved. The catalytic activity is negatively correlated with the pKa of the corresponding acid of the anhydride.
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Santry LJ, Poirier RA, McClelland RA, Csizmadia IG. The ring-opening of an unsymmetrical tetrahedral intermediate - 2-hydroxy-1,3-oxathiolane. Theor Chem Acc 1984. [DOI: 10.1007/bf01064209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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29
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30
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Capon B, Grieve DM. The products of hydrolysis of 2,2-dimethoxy- and 2,2-diethoxy-tetrahydropyran. Tetrahedron Lett 1982. [DOI: 10.1016/s0040-4039(00)85723-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Brent DA, Chandrasurin P, Ragouzeos A, Hurlbert BS, Burke JT. Rearrangement of chloramphenicol-3-monosuccinate. J Pharm Sci 1980; 69:906-8. [PMID: 6249906 DOI: 10.1002/jps.2600690812] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The equilibrium mixture of chloramphenicol-3-monosuccinate and its alternate form at neutral pH in aqueous solution was reexamined. The structure of the alternate form was shown by mass specxtrometry and NMR spectroscopy to be chloramphenicol-1-monosuccinate and not the cyclic hemi-ortho ester reported previously.
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