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Regioselective Synthesis of Benzannulated [5,6]-Oxaspirolactones via Cu(II)-Catalyzed Cycloisomerization of 2-(5-Hydroxyalkynyl)benzoates. J Org Chem 2023. [PMID: 38010985 DOI: 10.1021/acs.joc.3c01751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Spiroketals and oxaspirolactones are widely found in biologically active natural products, serving as important structural motifs. In this study, we present a Cu(II)-catalyzed cascade cycloisomerization of 2-(5-hydroxyalkynyl)benzoates, enabling the regioselective synthesis of benzannulated [5,6]-oxaspirolactones containing an isochromen-1-one moiety. This strategy offers a rapid and efficient approach to access a diverse array of benzannulated [5,6]-oxaspirolactones. The methodology presented here showcases a broad substrate scope, delivering good yields and scalability up to gram scale. The structures of the oxaspirolactones were unequivocally confirmed through single-crystal X-ray analysis and by analogy using 1H and 13C{1H} NMR data.
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2
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Total Synthesis of Okaspirodiol. ChemistrySelect 2023. [DOI: 10.1002/slct.202300352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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3
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A Route to 5,5-Dithiospiroketals and to Long-Chain Monomers from the Biomass. Org Lett 2022; 24:2878-2882. [DOI: 10.1021/acs.orglett.2c00855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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4
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Ready Access to Benzannulated [5,5]-Oxaspirolactones Using Au(III)-Catalyzed Cascade Cyclizations. J Org Chem 2022; 87:3025-3041. [PMID: 35188770 DOI: 10.1021/acs.joc.1c02843] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This work showcases an unprecedented Au(III)-catalyzed cascade cyclization of 2-(4-hydroxyalkynyl)benzoates to access benzannulated [5,5]-oxaspirolactones related to biologically active natural products. This reaction proceeds through an initial 5-endo-dig mode of hydroalkoxylation of the alkynol segment to give the oxocarbenium species (via cyclic enol-ether) followed by the addition of carboxylate onto the oxocarbenium that delivers the oxaspirolactone scaffold. While testing this method's scope, we found that the steric and electronic environment of the hydroxyl group could alter the reaction pathway that delivers isochromenone through a competitive 6-endo-dig mode of attack of the carboxylate onto the tethered alkyne.
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5
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Mechanistic Study on Gold(I)-Catalyzed Unsaturated Spiroketalization Reaction. LETT ORG CHEM 2022. [DOI: 10.2174/1570178619666220105151953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Abstract:
The mechanism of metal-catalyzed spiroketalization of propargyl acetonide is explored by employing DFT with the B3LYP/6-31+G(d) method. Acetonide is used as a regioselective regulator in the formation of monounsaturated spiroketal. The energies of transition states, intermediates, reactants and products are calculated to provide new insight into the mechanism of the reaction. The energetic features, validation of the observed trends in regioselectivity are conferred in terms of electronic indices via FMO analysis. The presence of acetonide facilitates a stepwise spiroketalization as it masks the competing nucleophile, and thus hydroxyl group present, exclusively acts as a nucleophile. The vinyl gold intermediate 3 is formed from 2 via activation barrier TS1. This is the first ring formation, which is 6-exo-dig cyclization. The intermediate 3 is converted into allenyl ether 4, which isomerizes to the intermediate oxocarbenium ion 5 via activation barrier TS2. The intermediate 5 cyclizes to 6 via TS3. This is the second ring formation. The intermediate 6 on protodeauration turns into 6,6-monounsaturated spiroketal 7. It is concluded that acetonide as a protecting group serves the purpose, and thus a wide range of spiroketals can be prepared, regioselectivity.
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Abstract
A highly enantioselective synthesis of chiral heterobicyclic spiroketals is reported via a "one-pot" cyclopropanation-rearrangement (CP-RA) cascade reaction that is sequentially catalyzed by a chiral Rh(II) catalyst and tetrabutylammonium fluoride (TBAF). Exocyclic vinyl substrates form spirocyclopropanes with tert-butyldimethylsilyl-protected enoldiazoacetates in excellent yields and with excellent enantioselectivities when catalyzed by chiral dirhodium(II) carboxylates, and following desilylation with simultaneous rearrangement in the presence of TBAF, they give (S)-spiroketals in high yields with excellent chirality retention (>95% ee).
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8
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Asymmetric cycloisomerization/[3 + 2] cycloaddition for the synthesis of chiral spiroisobenzofuran-1,3′-pyrrolidine derivatives. Org Chem Front 2021. [DOI: 10.1039/d1qo01194d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
An asymmetric tandem cycloisomerization/[3 + 2] cycloaddition reaction of 2,2′-diester aziridine and 2-ethynyl benzyl alcohol with Au(i)/chiral N,N′-dioxide−Dy(iii) as a relay catalyst system was developed.
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9
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Dictating Thermodynamic Control through Tethering: Applications to Stereoselective Bis-Spiroketal Synthesis. Angew Chem Int Ed Engl 2020; 59:6622-6626. [PMID: 31991022 DOI: 10.1002/anie.201916270] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Indexed: 01/31/2023]
Abstract
Approaches to stereocontrol that invoke thermodynamic control fail when two or more potential products are energetically similar, but rational structural perturbations can be employed to break the energetic degeneracy and provide selective transformations. This manuscript illustrates that tethering is an effective approach for the stereoselective construction of bis-spiroketals with thermodynamically similar stereoisomers, providing a new approach to set remote stereocenters and prepare complex structures that have not previously been accessed stereoselectively.
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10
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Dictating Thermodynamic Control through Tethering: Applications to Stereoselective Bis‐Spiroketal Synthesis. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201916270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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11
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Re 2O 7-Catalyzed Approach to Spirocyclic Ether Formation from Acyclic Precursors: Observation of Remote Stereoinduction. Org Lett 2019; 21:5064-5067. [PMID: 31247770 PMCID: PMC7720882 DOI: 10.1021/acs.orglett.9b01660] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ketones that are flanked by an allylic alcohol and an alkene isomerize to spirocyclic ethers in the presence of Re2O7 through allylic alcohol transposition, oxocarbenium ion formation, and Prins cyclization. These processes provide significant increases in molecular complexity, with multiple stereocenters being set relative to a stereocenter in the substrate. Stereoselectivity arises from the initial reversible steps being more rapid than the final step, thereby allowing for thermodynamically controlled stereochemical equilibration prior to product formation.
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12
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Bicyclic acetals: biological relevance, scaffold analysis, and applications in diversity-oriented synthesis. Org Biomol Chem 2019; 17:1037-1052. [DOI: 10.1039/c8ob02808g] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The chemoinformatics analysis of fused, spiro, and bridged bicyclic acetals is instrumental for the DOS of natural product-inspired molecular collections.
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14
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Oxidative Catalytic Spiroketalization Leading to Diastereoselective Synthesis of Spiro[benzofuran-2,1′-isochromene]s. Adv Synth Catal 2018. [DOI: 10.1002/adsc.201701149] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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15
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16
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Ag/Brønsted Acid Co-Catalyzed Spiroketalization of β-Alkynyl Ketones toward Spiro[chromane-2,1′-isochromene] Derivatives. Org Lett 2017; 19:3831-3834. [DOI: 10.1021/acs.orglett.7b01705] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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17
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A bidirectional synthesis of spiroacetals via Rh(ii)-catalysed C-H insertion. Chem Commun (Camb) 2017; 53:4219-4221. [PMID: 28357432 DOI: 10.1039/c7cc00459a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Acyclic methylene acetals bearing two diazoester subunits have been converted to [5,5]-spiroacetals via bidirectional C-H insertion under Rh(ii) catalysis. Using a chiral Rh(ii) catalyst, the major diastereomer can be produced in high enantiomeric excess (89%).
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18
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Lewis acid catalyzed cascade annulation of alkynols with α-ketoesters: a facile access to γ-spiroketal-γ-lactones. Chem Commun (Camb) 2017; 53:6641-6644. [DOI: 10.1039/c7cc03668j] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A simple protocol for the synthesis of diverse unsaturated γ-spiroketal-γ-lactones has been developed by employing a Bi(OTf)3 catalyzed cascade annulation of alkynols with α-ketoesters via a dual (π and σ) activation process.
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19
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2,5-Oxyarylation of Furans: Synthesis of Spiroacetals via Palladium-Catalyzed Aerobic Oxidative Coupling of Boronic Acids with α-Hydroxyalkylfurans. Org Lett 2016; 18:3226-9. [DOI: 10.1021/acs.orglett.6b01472] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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20
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Heteroscorpionate Rare-Earth Catalysts for the Hydroalkoxylation/Cyclization of Alkynyl Alcohols. Organometallics 2016. [DOI: 10.1021/acs.organomet.6b00203] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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21
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Studies of the Mechanism and Origins of Enantioselectivity for the Chiral Phosphoric Acid-Catalyzed Stereoselective Spiroketalization Reactions. J Am Chem Soc 2015; 138:444-56. [DOI: 10.1021/jacs.5b12528] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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22
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23
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Asymmetric Synthesis of Spiroketals with Aminothiourea Catalysts. Angew Chem Int Ed Engl 2015; 54:15497-500. [DOI: 10.1002/anie.201508405] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Indexed: 11/11/2022]
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24
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Didecarboxylative Iron-Catalyzed Bidirectional Aldolization towards Diversity-Oriented Ketodiol Synthesis. Chemistry 2015; 21:14717-22. [PMID: 26332439 DOI: 10.1002/chem.201502788] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Indexed: 11/10/2022]
Abstract
1,3-Acetonedicarboxylic acid was selectively activated by Fe(acac)3 , providing a synthetic platform for rapid synthesis of keto-3,3'-diols. The bidirectional aldol reaction was efficient for challenging aliphatic aldehydes, providing a rapid route to potentially bioactive complex structures.
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25
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Structure and conformational analysis of spiroketals from 6-O-methyl-9(E)-hydroxyiminoerythronolide A. Beilstein J Org Chem 2015; 11:1447-57. [PMID: 26425201 PMCID: PMC4578343 DOI: 10.3762/bjoc.11.157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 07/23/2015] [Indexed: 11/23/2022] Open
Abstract
Three novel spiroketals were prepared by a one-pot transformation of 6-O-methyl-9(E)-hydroxyiminoerythronolide A. We present the formation of a [4.5]spiroketal moiety within the macrolide lactone ring, but also the unexpected formation of a 10-C=11-C double bond and spontaneous change of stereochemistry at position 8-C. As a result, a thermodynamically stable structure was obtained. The structures of two new diastereomeric, unsaturated spiroketals, their configurations and conformations, were determined by means of NMR spectroscopy and molecular modelling. The reaction kinetics and mechanistic aspects of this transformation are discussed. These rearrangements provide a facile synthesis of novel macrolide scaffolds.
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27
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Enantioselective Syntheses of Spiroketals via a Tandem Reaction of Cu(I)-Catalyzed Cycloetherification and Hydrogen-Bond-Induced [4 + 2] Cyclization. J Org Chem 2015; 80:4189-200. [DOI: 10.1021/acs.joc.5b00384] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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28
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Abstract
Tertiary organolithium reagents have great potential in natural product synthesis. Recent progress in organolithium generation has made them accessible. Their utility and stereoselectivity in synthesis is discussed.
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29
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Stereoselective synthesis of 1,6-dioxaspirolactones from spiro-cyclopropanecarboxylated sugars: total synthesis of dihydro-pyrenolide D. RSC Adv 2015. [DOI: 10.1039/c4ra16753h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A one-pot protocol for the stereoselective construction of γ-spiroketal γ-lactone frameworks from sugar derived spiro-cyclopropanecarboxylic acids involving a ring enlargement and cyclization reaction is revealed.
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30
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Spiroacetal formation through telescoped cycloaddition and carbon-hydrogen bond functionalization: total synthesis of bistramide A. Angew Chem Int Ed Engl 2014; 53:11075-8. [PMID: 25196585 PMCID: PMC4234310 DOI: 10.1002/anie.201406819] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Indexed: 11/07/2022]
Abstract
Spiroacetals can be formed through a one-pot sequence of a hetero-Diels-Alder reaction, an oxidative carbon-hydrogen bond cleavage, and an acid treatment. This convergent approach expedites access to a complex molecular subunit which is present in numerous biologically active structures. The utility of the protocol is demonstrated through its application to a brief synthesis of the actin-binding cytotoxin bistramide A.
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31
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Spiroacetal Formation through Telescoped Cycloaddition and Carbon-Hydrogen Bond Functionalization: Total Synthesis of Bistramide A. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201406819] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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An Approach toward Constructing the Trioxadispiroketal Core in the DEF-Ring of (+)-Spirastrellolide A. Org Lett 2014; 16:4550-3. [DOI: 10.1021/ol502103b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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33
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34
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Spiroaminals - Crystal Structure and Computational Investigation of Conformational Preferences and Tautomerization Reactions. European J Org Chem 2014. [DOI: 10.1002/ejoc.201402576] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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35
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36
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Synthesis of 5,6- and 6,6-Spirocyclic Compounds. SYNTHESIS OF SATURATED OXYGENATED HETEROCYCLES I 2014. [DOI: 10.1007/978-3-642-41473-2_5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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37
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38
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Spiro- and Bicycloannulation of Sulfoximine-Substituted 2-Hydroxy-dihydropyrans: Enantioselective Synthesis of Spiroketals, Spiroethers, and Oxabicycles and Structure of Dihydropyran Oxocarbenium Ions. European J Org Chem 2013. [DOI: 10.1002/ejoc.201301461] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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39
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Practical Asymmetric Catalytic Synthesis of Spiroketals and Chiral Diphosphine Ligands. Adv Synth Catal 2013. [DOI: 10.1002/adsc.201300380] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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40
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Diacetoxyiodobenzene-mediated synthesis of unnatural furospirostane sapogenins derived from diosgenin and tigogenin. Steroids 2013; 78:798-802. [PMID: 23707570 DOI: 10.1016/j.steroids.2013.05.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 04/29/2013] [Accepted: 05/16/2013] [Indexed: 10/26/2022]
Abstract
Two unnatural steroid sapogenins bearing a furospirostane side chain were prepared starting from the readily available spirostane sapogenins, tigogenin and diosgenin following a synthetic protocol that included: (i) introduction of a carbonyl group at position C-23, (ii) diacetoxyiodobenzene-induced F-ring contraction and (iii) LiAlH4 reduction of the newly emerged methoxycarbonyl moiety. The structures of the new compounds were corroborated by NMR and X-ray studies.
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41
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A carbohydrate based chiron approach to the lactone intermediate employed in the synthesis of BC-ring fragment of (+)-spirastrellolide A. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.07.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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42
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Mechanistic insights on the reactivity of furospirostanes with the 16β,22:22,25-diepoxy-23-acetoxymethyl-24-methyl side chain. Steroids 2013; 78:787-97. [PMID: 23707575 DOI: 10.1016/j.steroids.2013.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 04/16/2013] [Accepted: 05/09/2013] [Indexed: 11/27/2022]
Abstract
F-ring opening in spirostanes with the 16β,22:22,25-diepoxy-23-acetoxymethyl-24-methyl side chain produces a Δ(22)-intermediate with an allylic acetoxy group. For this reason the reactivity profile of these compounds deviates from that observed in other naturally occurring or synthetic spirostanes and furospirostanes.
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44
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A Concise and Efficient Synthesis of Spiroketals - Application to the Synthesis of SPIKET-P and a Spiroketal fromBactroceraSpecies. European J Org Chem 2013. [DOI: 10.1002/ejoc.201201199] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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45
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Enantioselective synthesis of spiroacetals via silver(I)-promoted alkylation of hemiacetals: total synthesis of cephalosporolides E and F. Org Lett 2012; 14:5844-7. [PMID: 23145960 DOI: 10.1021/ol302694s] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A silver(I)-promoted intramolecular hemiacetal alkylation has been developed that converts readily available keto-chlorodiols into functionalized spiroacetals containing 5,5-, 5,6-, and 5,7-membered ring systems. The efficiency of this process is demonstrated in a concise total synthesis of the fungal metabolites cephalosporolides E and F.
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4-[5-(3,5-Difluorophenyl)furan-2-yl]-2,3,7-triazaspiro[4.5]dec-3-en-1-one Hydrochloride. MOLBANK 2012. [DOI: 10.3390/m773] [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] Open
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49
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3-(4-Fluorophenyl)-N-[4-(4-furan-2-yl-1-oxo-2,3,7-triazaspiro[4.5]dec-3-en-2-yl)phenyl]propionamide Hydrochloride. MOLBANK 2012. [DOI: 10.3390/m771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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50
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On the proposed structures and stereocontrolled synthesis of the cephalosporolides. Beilstein J Org Chem 2012; 8:1287-92. [PMID: 23019461 PMCID: PMC3458751 DOI: 10.3762/bjoc.8.146] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 07/14/2012] [Indexed: 11/23/2022] Open
Abstract
The synthesis of four candidate stereoisomers of cephalosporolide H is described, made possible by a zinc-chelation strategy for controlling the stereochemistry of oxygenated 5,5-spiroketals. The same strategy likewise enables the first stereocontrolled synthesis of cephalosporolide E, which is typically isolated and prepared admixed with its spiroketal epimer, cephalosporolide F.
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