1
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Dulcisenes C-E, polyoxygenated cyclohexenes, from Uvaria dulcis dunal and their cytotoxic activity. PHYTOCHEMISTRY 2022; 202:113298. [PMID: 35780925 DOI: 10.1016/j.phytochem.2022.113298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 06/15/2022] [Accepted: 06/27/2022] [Indexed: 06/15/2023]
Abstract
Dulcisenes C-E, undescribed polyoxygenated cyclohexenes and twenty-one known compounds were isolated from the dichloromethane extract of the leaves of Uvaria dulcis Dunal. The structures of these undescribed compounds were determined by spectroscopic data analyses, including 1D and 2D NMR, IR, and MS techniques; their absolute configurations were analyzed by NOESY and ECD spectra. Cytotoxicity of sixteen more abundant isolates was evaluated. Cherrevenone and 2',3'-dihydroxy-4',6'-dimethoxychalcone exhibited cytotoxic activity against some cancer cell lines with IC50 values in the range of 3.3-11.8 μM.
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2
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Alcohol-Incorporating Diels-Alder Dimerization of In Situ Formed ortho-Quinamine via Co-Nitrenoid Insertion. Org Lett 2022; 24:5845-5850. [PMID: 35916774 DOI: 10.1021/acs.orglett.2c02392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We disclose herein a Cp*Co(III)(LX)-catalyzed dearomative Diels-Alder dimerization of 2,6-disubstituted phenyl azidoformates. Upon the postulated cobalt-nitrenoid insertion into the neighboring ortho-carbon, the key intermediate of ortho-quinamine was generated for the subsequent dimeric cycloaddition process. A series of experimental and computational studies suggested that the quinolinol ligand of the cobalt catalyst plays a crucial role in the alcoholic solvent incorporation into the o-quinamine moiety, thereby enabling the Diels-Alder dimerization to furnish the bridged tricyclic bisamidation products.
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3
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1,2-Rearrangement from o-Quinols to Multisubstituted Catechols via Retro Diels-Alder Reaction of o-Quinol Dimers. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2022. [DOI: 10.1246/bcsj.20220025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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4
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Synthesis of pleiogenone A and 2,3-dihydropleiogenone A: Identification of the pleiogenone pharmacophore. Tetrahedron Lett 2021. [DOI: 10.1016/j.tetlet.2021.153393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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5
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Bispericyclic Diels–Alder Dimerization of
ortho
‐Quinols in Natural Product (Bio)Synthesis: Bioinspired Chemical 6‐Step Synthesis of (+)‐Maytenone. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202103410] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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6
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Bispericyclic Diels-Alder Dimerization of ortho-Quinols in Natural Product (Bio)Synthesis: Bioinspired Chemical 6-Step Synthesis of (+)-Maytenone. Angew Chem Int Ed Engl 2021; 60:14967-14974. [PMID: 33851775 DOI: 10.1002/anie.202103410] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Indexed: 12/15/2022]
Abstract
Many natural products of plant or microbial origins are derived from enzymatic dearomative oxygenation of 2-alkylphenolic precursors into 6-alkyl-6-hydroxycyclohexa-2,4-dienones. These so-called ortho-quinols cyclodimerize via a remarkably selective bispericyclic Diels-Alder reaction. Whether or not the intervention of catalytic or dirigent proteins is involved during this final step of the biosynthesis of these natural products, this cyclodimerization of ortho-quinols can be chemically reproduced in the laboratory with the same strict level of site-specific regioselectivity and stereoselectivity. This unique yet unified process, which finds its rationale in the inherent chemical reactivity of those ortho-quinols, is illustrated herein by an efficient and bioinspired first chemical synthesis of one of the most structurally complex and synthetically challenging examples of such natural cyclodimers, the bisditerpenoid (+)-maytenone.
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7
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Miyabeacin: A new cyclodimer presents a potential role for willow in cancer therapy. Sci Rep 2020; 10:6477. [PMID: 32296088 PMCID: PMC7160102 DOI: 10.1038/s41598-020-63349-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 03/27/2020] [Indexed: 02/08/2023] Open
Abstract
Willow (Salix spp.) is well known as a source of medicinal compounds, the most famous being salicin, the progenitor of aspirin. Here we describe the isolation, structure determination, and anti-cancer activity of a cyclodimeric salicinoid (miyabeacin) from S. miyabeana and S. dasyclados. We also show that the capability to produce such dimers is a heritable trait and how variation in structures of natural miyabeacin analogues is derived via cross-over Diels-Alder reactions from pools of ortho-quinol precursors. These transient ortho-quinols have a role in the, as yet uncharacterised, biosynthetic pathways around salicortin, the major salicinoid of many willow genotypes.
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8
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Sidechain Diversification of Grandifloracin Allows Identification of Analogues with Enhanced Anti-Austerity Activity against Human PANC-1 Pancreatic Cancer Cells. ChemMedChem 2020; 15:125-135. [PMID: 31821731 PMCID: PMC7003952 DOI: 10.1002/cmdc.201900549] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 11/11/2019] [Indexed: 12/25/2022]
Abstract
The natural product (+)-grandifloracin is a potent "anti-austerity" agent, able to suppress the ability of various pancreatic cancer cell lines to tolerate conditions of nutrient deprivation. Such anti-austerity agents represent a promising approach to cancer chemotherapy. Here we report the synthesis and biological evaluation of racemic analogues of grandifloracin bearing diverse sidechains, of which two show enhanced potency in comparison with the natural product. Additionally, several unexpected by-products containing modifications of the grandifloracin core were isolated, identified and similarly evaluated for biological activity.
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9
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Enantioselective Synthesis of Arene
cis
‐Dihydrodiols from 2‐Pyrones. Angew Chem Int Ed Engl 2019; 58:14562-14567. [DOI: 10.1002/anie.201908284] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Indexed: 01/13/2023]
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10
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11
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Site‐selective Oxidative Dearomatization of Phenols and Naphthols into
ortho
‐Quinols or Epoxy
ortho
‐Quinols using Oxone as the Source of Dimethyldioxirane. Adv Synth Catal 2019. [DOI: 10.1002/adsc.201900660] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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12
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Benefits of Unconventional Methods in the Total Synthesis of Natural Products. ACS OMEGA 2018; 3:17326-17340. [PMID: 30613812 PMCID: PMC6312638 DOI: 10.1021/acsomega.8b02994] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 11/27/2018] [Indexed: 06/09/2023]
Abstract
This article provides a survey of four "unconventional" methods employed in the synthesis of natural products in the Hudlicky group. The utility of flash vacuum pyrolysis is highlighted by examples of many natural products attained via vinylcyclopropane-cyclopentene rearrangement and its heterocyclic variants. Preparative organic electrochemistry was used in oxidations and reductions with levels of selectivity unattainable by conventional methods. Yeast reduction of ketoesters was featured in the total synthesis of pyrrolizidine alkaloids. Finally, the use of toluene dioxygenase-mediated dihydroxylations in enantioselective synthesis of natural products concludes this presentation. Recently, synthesized targets in the period 2010-2019 are listed in the accompanying table. The results of research from the Hudlicky group are placed in appropriate context with the work of others, and a detailed guide to the current literature is provided.
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13
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Chemical Constituents of Thai Citrus hystrix and Their Antiausterity Activity against the PANC-1 Human Pancreatic Cancer Cell Line. JOURNAL OF NATURAL PRODUCTS 2018; 81:1877-1883. [PMID: 30070833 DOI: 10.1021/acs.jnatprod.8b00405] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Human pancreatic cancer cells have an extreme tolerance to nutrition starvation, enabling them to survive in a hypovascular tumor microenvironment. Searching for agents that preferentially inhibit cancer cell viability under nutrition starvation conditions is a novel antiausterity strategy in anticancer drug discovery. In the present study, a hexane extract of the peels of Citrus hystrix fruits showed preferential cytotoxicity against PANC-1 human pancreatic cancer cells using a nutrient-deprived medium. Phytochemical investigation of this bioactive extract led to the isolation of 10 coumarins (1-10) including a new furanocoumarin (1). The isolated compounds were tested for their preferential cytotoxic activity against three different human pancreatic cancer cell lines [PANC-1, MIA PaCa-2, and PSN-1]. Among these, bergamottin (7) was identified as the most active constituent. In real-time live imaging, 7 was found to induce cell shrinkage, membrane blebbing, and disintegration of organelles in PANC-1 cells. Bergamottin (7) was also found to inhibit PANC-1 cell migration and colony formation. Mechanistically, 7 inhibited key survival proteins in the Akt/mTOR signaling pathway. Bergamottin (7) and related compounds are potential antiausterity candidates for drug development against pancreatic cancer.
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14
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Synthesis of 1,3-Cycloalkadienes from Cycloalkenes: Unprecedented Reactivity of Oxoammonium Salts. Angew Chem Int Ed Engl 2018; 55:13189-13194. [PMID: 27650040 DOI: 10.1002/anie.201607752] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Indexed: 01/14/2023]
Abstract
Few methods allow for the direct conversion of cycloalkenes into cycloalkadienes with high chemo- and regioselectivity. Herein, we report a convenient one-pot process for this transformation that involves the unprecedented N-preferential group transfer of N-oxoammonium salts to cycloalkenes, followed by Cope elimination, to afford cycloalkadienes at room temperature and pressure.
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15
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Production of enantiopure β-amino-γ-hydroxyesters from benzoic acid by a selective formal aminohydroxylation. Tetrahedron Lett 2017. [DOI: 10.1016/j.tetlet.2017.04.048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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16
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Highly oxygenated antiausterity agents from the leaves of Uvaria dac. Bioorg Med Chem Lett 2017; 27:1967-1971. [DOI: 10.1016/j.bmcl.2017.03.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 02/24/2017] [Accepted: 03/09/2017] [Indexed: 02/02/2023]
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17
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A Formal Approach to Xylosmin and Flacourtosides E and F: Chemoenzymatic Total Synthesis of the Hydroxylated Cyclohexenone Carboxylic Acid Moiety of Xylosmin. Org Lett 2017; 19:1156-1159. [DOI: 10.1021/acs.orglett.7b00194] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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18
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The Synthesis of Certain Phomentrioloxin A Analogues and Their Evaluation as Herbicidal Agents. J Org Chem 2016; 82:211-233. [DOI: 10.1021/acs.joc.6b02372] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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19
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Synthesis of 1,3-Cycloalkadienes from Cycloalkenes: Unprecedented Reactivity of Oxoammonium Salts. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201607752] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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20
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21
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Chemoenzymatic Synthesis of Pleiogenone A: An Antiproliferative Trihydroxyalkylcyclohexenone Isolated from Pleiogynium timorense. Chemistry 2016; 22:6180-4. [PMID: 26956129 DOI: 10.1002/chem.201601061] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Indexed: 02/01/2023]
Abstract
The first total synthesis of polyhydroxylated cyclohexenone 1, isolated from Pleiogynium timorense and named pleiogenone A, is reported that also serves as a proof of structure and absolute configuration. Enzymatic dihydroxylation of benzoic acid with R. eutrophus B9 provided enantiomerically pure diene diol 6. Elaboration of the carboxylate moiety to the alkyl side chain was followed by singlet oxygen cycloaddition to furnish an endoperoxide whose reduction with thiourea led to cyclitol 19. Several protective operations were required before oxidation and the final extension of the side chain by a Wittig reaction. After final deprotection of the acetonide functionality the desired pleiogenone A (1) was obtained in 14 operations from benzoic acid.
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22
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Total syntheses of five uvacalols: structural validation of uvacalol A, uvacalol B and uvacalol C and disproval of the structures of uvacalol E and uvacalol G. Org Biomol Chem 2015; 13:3900-10. [PMID: 25655990 DOI: 10.1039/c4ob02663b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Uvacalols are novel carbasugars belonging to the family of C7-cyclitols, and are isolated from the roots of the medicinal plant, Uvaria calamistrata. In this study, we report the first syntheses of five uvacalols starting from a cheap and easily available chiral pool starting material, D-mannitol, in their optically pure form. D-Mannitol was converted to the alkene 2 through a series of regioselective and chemoselective transformations by following our previously reported strategies. Alkene 2 was converted to the enal 5 through a series of protective group manipulations. Enal 5 was converted to the diene 6 by the addition of vinyl magnesium bromide. Ring closing metathesis of the diene 6 using Grubbs’ second generation catalyst installed the core cyclohexenyl unit. Through several iterative and selective manipulations of various hydroxyl groups, uvacalol A, uvacalol B, uvacalol C, uvacalol E and uvacalol G were synthesized. A comparison of the (1)H NMR and (13)C NMR data of these synthesized molecules with the reported data, revealed that the reported structures of uvacalols A–C are correct and those of uvacalols E and G are wrong.
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23
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Tricarbonyliron(0) complexes of bio-derived η4 cyclohexadiene ligands: An approach to analogues of oseltamivir. J Organomet Chem 2015. [DOI: 10.1016/j.jorganchem.2015.09.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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24
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25
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Abstract
A highly efficient regio- and stereoselective total synthesis of (±)-grandifloracin via a tandem dearomative epoxidation/spontaneous Diels-Alder cyclodimerization from salicylic acid in only four steps is reported. The synthetic route allows for late-stage diversification of the core structure to give ready access to analogues of this promising agent against pancreatic cancer.
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26
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First Total Synthesis of Piperenol B and Configuration Revision of the Enantiomers Piperenol B and Uvarirufol A. European J Org Chem 2015. [DOI: 10.1002/ejoc.201403582] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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27
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An approach towards expanding the scope of masked o-benzoquinone dimers to generate diverse compound libraries. RSC Adv 2015. [DOI: 10.1039/c5ra03627e] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In this report, a simple and rapid approach for the synthesis of masked o-benzoquinone (MOB) heterodimers is presented.
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28
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Stereospecific synthesis of highly substituted novel carbasugar as carbonic anhydrase inhibitors: decahydronaphthalene-1,2,3,4,5,6,7-heptol. Tetrahedron 2014. [DOI: 10.1016/j.tet.2014.05.101] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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29
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The enone motif of (+)-grandifloracin is not essential for ‘anti-austerity’ antiproliferative activity. Bioorg Med Chem Lett 2014; 24:2815-9. [DOI: 10.1016/j.bmcl.2014.04.111] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 04/25/2014] [Accepted: 04/27/2014] [Indexed: 02/06/2023]
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30
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Abstract
Monocyclic allylic cis-1,2-diols reacted with sulfuryl chloride at 0 °C in a regio- and stereo-selective manner to give 2-chloro-1-sulfochloridates, which were hydrolysed to yield the corresponding trans-1,2-chlorohydrins. At -78 °C, with very slow addition of sulfuryl chloride, cyclic sulfates were formed in good yields, proved to be very reactive with nucleophiles and rapidly decomposed on attempted storage. Reaction of a cyclic sulfate with sodium azide yielded a trans-azidohydrin without evidence of allylic rearrangement occurring. An enantiopure bicyclic cis-1,2-diol reacted with sulfuryl chloride to give, exclusively, a trans-1,2-dichloride enantiomer with retention of configuration at the benzylic centre and inversion at the non-benzylic centre; a mechanism is presented to rationalise the observation.
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31
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Applications of biocatalytic arene ipso,ortho cis-dihydroxylation in synthesis. Chem Commun (Camb) 2014; 50:2821-30. [PMID: 24514270 DOI: 10.1039/c3cc49694e] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The dearomatising dihydroxylation of aromatic molecules mediated by arene dioxygenase enzymes can provide cyclohexadiene-diols that are versatile starting materials for organic synthesis. Whereas oxidation of a substituted arene to give its ortho,meta-dihydrodiol has been demonstrated for numerous substrates and dioxygenases, formation of ipso,ortho-dihydrodiols has historically been underutilised in comparison. This feature article presents a chronological account of reported uses of such diols.
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32
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Processing of o-Halobenzoates by Toluene Dioxygenase. The Role of the Alkoxy Functionality in the Regioselectivity of the Enzymatic Dihydroxylation Reaction. Org Process Res Dev 2014. [DOI: 10.1021/op400343c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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33
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Benzoate dioxygenase fromRalstonia eutrophaB9 – unusual regiochemistry of dihydroxylation permits rapid access to novel chirons. Org Chem Front 2014. [DOI: 10.1039/c3qo00057e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Oxidation of benzoic acid by a microorganism expressing benzoate dioxygenase leads to the formation of an unusualipso,orthoarenecis-diol in sufficient quantities to be useful for synthesis.
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34
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35
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Chemoenzymatic total synthesis of the phytotoxic geranylcyclohexentriol (-)-phomentrioloxin. JOURNAL OF NATURAL PRODUCTS 2013; 76:1514-8. [PMID: 23895674 DOI: 10.1021/np4002866] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The enantiomeric form, 1R, of the structure (1S) assigned to the phytotoxic natural product phomentrioloxin has been synthesized in seven steps from the homochiral cis-1,2-dihydrocatechol 3. These studies reveal that the true structure of phomentrioloxin is represented by 1R and not by 1S.
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36
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Reactions of nitrogen nucleophiles with enantiopure cyclohexenyl electrophiles: a stereo- and regio- selective study. J PHYS ORG CHEM 2013. [DOI: 10.1002/poc.3183] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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37
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New aminocyclitols with quaternary stereocentres via acylnitroso cycloaddition with an ipso,ortho arene dihydrodiol. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.04.033] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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38
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Chiral Anion Phase-Transfer Catalysis Applied to the Direct Enantioselective Fluorinative Dearomatization of Phenols. J Am Chem Soc 2013; 135:1268-71. [DOI: 10.1021/ja311798q] [Citation(s) in RCA: 198] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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39
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Regiodirecting effects in difunctionalised tricarbonyl[(1,2,3,4,5-η)-cyclohexadienyl]iron(1+) salts: building blocks for alkaloids. Tetrahedron Lett 2013. [DOI: 10.1016/j.tetlet.2012.09.086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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40
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Stereochemical requirements of oxidative cyclizations in extended iterative organoiron-mediated routes to alkaloids. J Org Chem 2012; 77:9684-92. [PMID: 23066933 DOI: 10.1021/jo301617f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxidative cyclization by reaction of benzylic and phenolic OH groups on tricarbonyl(η(4)-cyclohexa-1,3-diene)iron(0) complexes has been achieved with the hypervalent iodine oxidant PIFA which was shown to be compatible with the tricarbonyliron complex. The reaction proceeds with substrates with the nucleophilic substituent on the opposite face of the ligand to the iron. IBX gives efficient oxidation of the benzyl alcohol to the aldehyde in the presence of the Fe(CO)(3) group. Reduction of 1-arylcyclohexadienyliron(1+) complexes with sodium borohydride to access the endo series also gave a novel rearranged 2-aryl reduction product with a 5-endo OMe group. The cis relative stereochemistry of the oxidative cyclization product, the exo delivery of hydride to the 1-arylcyclohexadienyliron(1+) complex, and the 2-aryl-5-endo-methoxy relative stereochemistry of the rearranged product were proved by X-ray crystallography.
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41
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Valuable New Cyclohexadiene Building Blocks from Cationic η5-Iron-Carbonyl Complexes Derived from a Microbial Arene Oxidation Product. Chemistry 2012; 18:13480-93. [DOI: 10.1002/chem.201202411] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Indexed: 11/08/2022]
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42
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Influencing the Balance between ipso and ω Nucleophile Addition to (1-Arylcyclohexadienyl)iron Intermediates in Alkaloid Synthesis. European J Org Chem 2012. [DOI: 10.1002/ejoc.201200687] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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43
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Antiausterity agents from Uvaria dac and their preferential cytotoxic activity against human pancreatic cancer cell lines in a nutrient-deprived condition. JOURNAL OF NATURAL PRODUCTS 2012; 75:1177-1183. [PMID: 22676269 DOI: 10.1021/np300295h] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Human pancreatic cancer cell lines are known for their inherent tolerance to nutrition starvation, which enables them to survive under a hypovascular (austerity) tumor microenvironment. The search for agents that preferentially retard the survival of cancer cells under low nutrition conditions (antiausterity agent) is a novel approach to anticancer drug discovery. In this study, it was found that a dichloromethane extract of the stem of Uvaria dac preferentially inhibited PANC-1 human pancreatic cancer cells survival under nutrition-deprived conditions at a concentration of 10 μg/mL. Workup of this bioactive extract led to the discovery of (+)-grandifloracin (8) as a potent antiausterity agent as evaluated in a panel of four human pancreatic cancer cell lines, PANC-1 (PC(50), 14.5 μM), PSN-1 (PC(50), 32.6 μM), MIA PaCa-2 (PC(50), 17.5 μM), and KLM-1 (32.7 μM). (+)-Grandifloracin (8) has been isolated from a natural source for the first time. Its absolute stereochemistry was established by single-crystal X-ray crystallography and circular dichroism spectroscopic analysis. In addition to this, seven other new highly oxygenated cyclohexene derivatives, named uvaridacanes A (1) and B (2), uvaridacols A-D (3, 4, 6, 7), and uvaridapoxide A (5), were also isolated and structurally characterized.
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Photooxygenation of a Microbial Arene Oxidation Product and Regioselective Kornblum-DeLaMare Rearrangement: Total Synthesis of Zeylenols and Zeylenones. Chemistry 2012; 18:4766-74. [DOI: 10.1002/chem.201104035] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Indexed: 11/11/2022]
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A cobalt complex of a microbial arene oxidation product. Chem Cent J 2011; 5:80. [PMID: 22152033 PMCID: PMC3268747 DOI: 10.1186/1752-153x-5-80] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/07/2011] [Indexed: 11/10/2022] Open
Abstract
We report the first synthesis of a cobalt Cp diene complex wherein the diene is derived by microbial dearomatising dihydroxylation of an aromatic ring. The complex has been characterised crystallographically and its structure is compared to that of an uncomplexed diene precursor.
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