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Masiuk US, Faletrov YV, Kananovich DG, Mineyeva IV. Stereodivergent Assembly of 2,6- cis- and - trans-Tetrahydropyrans via Base-Mediated Oxa-Michael Cyclization: The Key Role of the TMEDA Additive. J Org Chem 2023; 88:355-370. [PMID: 36495268 DOI: 10.1021/acs.joc.2c02382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The stereodivergent synthesis of cis- and trans-2,6-disubstituted tetrahydropyrans (THPs) via sodium hexamethyldisilazide-promoted oxa-Michael cyclization of (E)-ζ-hydroxy α,β-unsaturated esters is presented. The cyclization affords the kinetically favored trans-THPs with high stereoselectivity (dr up to 93:7) at a low temperature (-78 °C), while the room-temperature reaction does not produce the thermodynamically preferred cis-THPs as major products and occurs with poor stereocontrol. The addition of tetramethylethylenediamine (TMEDA) significantly improves the stereochemical outcome of the room-temperature cyclization and allows attaining high cis-selectivity (dr up to 99:1). The remarkable effect of TMEDA indicates that the sodium cation plays an important role in controlling the stereoselectivity of the thermodynamically driven process, that is, complexation of the cation with the cyclization products results in diminished selectivity. DFT calculations support this conclusion, indicating a greater difference in Gibbs energies of sodium-free cis- and trans-enolates compared to the respective sodium chelate complexes. The synthetic utility of the method has been demonstrated by the formal syntheses of (+)-Neopeltolide and (-)-Diospongin B and the total synthesis of (-)-Diospongin A.
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Affiliation(s)
- Uladzimir S Masiuk
- Department of Chemistry, Belarusian State University, Leningradskaya 14, 220006 Minsk, Belarus.,School of Science, Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Yaroslav V Faletrov
- Department of Chemistry, Belarusian State University, Leningradskaya 14, 220006 Minsk, Belarus.,Research Institute for Physical Chemical Problems, Belarusian State University, Leningradskaya 14, 220006 Minsk, Belarus
| | - Dzmitry G Kananovich
- School of Science, Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Iryna V Mineyeva
- Department of Chemistry, Belarusian State University, Leningradskaya 14, 220006 Minsk, Belarus
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Kataria P, Nomula R, Kontham R. Studies directed toward the synthesis of hedycoropyrans: total synthesis of des-hydroxy (-)-hedycoropyran B ( ent-rhoiptelol B). Org Biomol Chem 2022; 20:444-463. [PMID: 34904991 DOI: 10.1039/d1ob01972d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A full account of our efforts directed towards the synthesis of the diarylheptanoid-derived natural products hedycoropyrans that led to the total synthesis of ent-rhoiptelol B is described. In this endeavor, we have attempted two distinct synthetic strategies to access hedycoropyrans A and B, which led us to establish a facile synthetic route for des-hydroxy (-)-hedycoropyran B (ent-rhoiptelol B) from simple and readily accessible building blocks of 4-allylanisole and vanillin, employing Sharpless asymmetric epoxidation, CBS reduction, and an intramolecular AgOTf-catalyzed oxa-Michael reaction of suitably functionalized hydroxy-ynone as key transformations. The investigations disclosed herein will provide insights into designing novel synthetic routes for THP-DAH-derived natural products.
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Affiliation(s)
- Priyanka Kataria
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India. .,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Rajesh Nomula
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.
| | - Ravindar Kontham
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India. .,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
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Hollmann T, Berkhan G, Wagner L, Sung KH, Kolb S, Geise H, Hahn F. Biocatalysts from Biosynthetic Pathways: Enabling Stereoselective, Enzymatic Cycloether Formation on a Gram Scale. ACS Catal 2020. [DOI: 10.1021/acscatal.9b05071] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Tim Hollmann
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Gesche Berkhan
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
- Centre for Biomolecular Drug Research, Leibniz Universität Hannover, Schneiderberg 38, 30167 Hannover, Germany
| | - Lisa Wagner
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Kwang Hoon Sung
- Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstrasse 7, 38124 Braunschweig, Germany
- Institute of Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
- Protein Facility, ILAb Co., Ltd. NP513, The Catholic University of Korea, 420-743 Bucheon, Republic of Korea
| | - Simon Kolb
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Hendrik Geise
- Centre for Biomolecular Drug Research, Leibniz Universität Hannover, Schneiderberg 38, 30167 Hannover, Germany
| | - Frank Hahn
- Professur für Organische Chemie (Lebensmittelchemie), Fakultät für Biologie, Chemie und Geowissenschaften, Department of Chemistry, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
- Centre for Biomolecular Drug Research, Leibniz Universität Hannover, Schneiderberg 38, 30167 Hannover, Germany
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Csókás D, Ho AXY, Ramabhadran RO, Bates RW. How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition. Org Biomol Chem 2019; 17:6293-6304. [PMID: 31204752 DOI: 10.1039/c9ob00750d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The intramolecular oxa-Michael addition giving tetrahydropyrans has been examined experimentally using both acidic and basic catalysis. With acidic catalysis, the diequatorial product is exclusively obtained in a kinetically controlled reaction in all cases. Under basic conditions at low temperature, the reaction is again under kinetic control, but formation of the axial-equatorial isomer is generally favoured with an (E)-Michael acceptor, although isomerisation to the diequatorial isomer is observed at higher temperatures. Computationally, it is found that the acid catalysed reaction has a late transition state and the kinetic favouring of the diequatorial isomer has a steric explanation. In contrast, under strongly basic conditions, an early transition state is found. Electrostatic effects are likely to be the main contributor to the stereoselectivity for the (E)-isomer and steric interactions for the (Z)-isomer.
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Affiliation(s)
- Dániel Csókás
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371, Singapore.
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Lee K, Lanier ML, Kwak JH, Kim H, Hong J. Advances in the synthesis of glycosidic macrolides: clavosolides A-D and cyanolide A. Nat Prod Rep 2017; 33:1393-1424. [PMID: 27714078 DOI: 10.1039/c6np00073h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Covering: 2005 to 2016Clavosolides A-D and cyanolide A are glycosidic macrolides and represent a new family of marine natural products. They possess a number of unusual structural features and have attracted considerable interest from the synthetic community. This review presents a comprehensive survey of all aspects of the clavosolides A-D and cyanolide A. Specific topics include isolation, structure determination, biological activity, and synthetic approaches.
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Affiliation(s)
- Kiyoun Lee
- Department of Chemistry, The Catholic University of Korea, Bucheon 14662, Republic of Korea.
| | - Megan L Lanier
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
| | - Jae-Hwan Kwak
- College of Pharmacy, Kyungsung University, Busan 48434, Republic of Korea.
| | - Hyoungsu Kim
- College of Pharmacy and Institute of Pharmaceutical Science and Technology, Ajou University, Suwon 16499, Republic of Korea.
| | - Jiyong Hong
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
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Ermanis K, Hsiao YT, Kaya U, Jeuken A, Clarke PA. The stereodivergent formation of 2,6- cis and 2,6- trans-tetrahydropyrans: experimental and computational investigation of the mechanism of a thioester oxy-Michael cyclization. Chem Sci 2017; 8:482-490. [PMID: 28451195 PMCID: PMC5298201 DOI: 10.1039/c6sc03478k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 08/26/2016] [Indexed: 11/24/2022] Open
Abstract
Computational and synthetic studies have elucidated the origins of stereodivergence in an oxy-Michael synthesis of 2,6-disubstituted tetrahydropyrans.
The origins of the stereodivergence in the thioester oxy-Michael cyclization for the formation of 4-hydroxy-2,6-cis- or 2,6-trans-substituted tetrahydropyran rings under different conditions was investigated both computationally and experimentally. Synthetic studies showed that the 4-hydroxyl group was essential for stereodivergence. When the 4-hydroxyl group was present, TBAF-mediated conditions gave the 2,6-trans-tetrahydropyran and trifluoroacetic acid-mediated conditions gave the 2,6-cis-tetrahydropyran. This stereodivergence vanished when the hydroxyl group was removed or protected. Computational studies revealed that: (i) the trifluoroacetic acid catalysed formation of 2,6-cis-tetrahydropyrans was mediated by a trifluoroacetate-hydroxonium bridge and proceeded via a chair-like transition state; (ii) the TBAF-mediated formation of 2,6-trans-tetrahydropyrans proceeded via a boat-like transition state, where the 4-hydroxyl group formed a crucial hydrogen bond to the cyclizing alkoxide; (iii) both reactions are under kinetic control. The utility of this stereodivergent approach for the formation of 4-hydroxy-2,6-substituted tetrahydropyran rings has been demonstrated by the total syntheses of the anti-osteoporotic natural products diospongin A and B.
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Affiliation(s)
- Kristaps Ermanis
- Department of Chemistry , University of York , Heslington , York , North Yorkshire YO10 5DD , UK .
| | - Yin-Ting Hsiao
- Department of Chemistry , University of York , Heslington , York , North Yorkshire YO10 5DD , UK .
| | - Uğur Kaya
- Department of Chemistry , University of York , Heslington , York , North Yorkshire YO10 5DD , UK .
| | - Alan Jeuken
- Department of Chemistry , University of York , Heslington , York , North Yorkshire YO10 5DD , UK .
| | - Paul A Clarke
- Department of Chemistry , University of York , Heslington , York , North Yorkshire YO10 5DD , UK .
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Cossy J, Guérinot A. Natural Products Containing Oxygen Heterocycles—Synthetic Advances Between 1990 and 2015. ADVANCES IN HETEROCYCLIC CHEMISTRY 2016. [DOI: 10.1016/bs.aihch.2016.03.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Bates RW, Li L, Palani K, Phetsang W, Loh JK. Synthesis of the Tetrahydropyran Fragment of Bistramide D. ASIAN J ORG CHEM 2014. [DOI: 10.1002/ajoc.201402052] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Fuwa H, Kawakami M, Noto K, Muto T, Suga Y, Konoki K, Yotsu-Yamashita M, Sasaki M. Concise synthesis and biological assessment of (+)-neopeltolide and a 16-member stereoisomer library of 8,9-dehydroneopeltolide: identification of pharmacophoric elements. Chemistry 2013; 19:8100-10. [PMID: 23606326 DOI: 10.1002/chem.201300664] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Indexed: 02/01/2023]
Abstract
We describe herein a concise synthesis of (+)-neopeltolide, a marine macrolide natural product that elicits a highly potent antiproliferative activity against several human cancer cell lines. Our synthesis exploited the powerful bond-forming ability and high functional group compatibility of olefin metathesis and esterification reactions to minimize manipulations of oxygen functionalities and to maximize synthetic convergency. Our findings include a chemoselective olefin cross-metathesis reaction directed by H-bonding, and a ring-closing metathesis conducted under non-high dilution conditions. Moreover, we developed a 16-member stereoisomer library of 8,9-dehydroneopeltolide to systematically explore the stereostructure-activity relationships. Assessment of the antiproliferative activity of the stereoisomers against A549 human lung adenocarcinoma, MCF-7 human breast adenocarcinoma, HT-1080 human fibrosarcoma, and P388 murine leukemia cell lines has revealed marked differences in potency between the stereoisomers. This study provides comprehensive insights into the structure-activity relationship of this important antiproliferative agent, leading to the identification of the pharmacophoric structural elements and the development of truncated analogues with nanomolar potency.
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Affiliation(s)
- Haruhiko Fuwa
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
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11
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Weise CF, Immel S, Richter F, Schneider C. The Oxy-Cope Rearrangement of Aldol Products. A Combined Experimental and Theoretical Study. European J Org Chem 2012. [DOI: 10.1002/ejoc.201101690] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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12
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Fuwa H, Ichinokawa N, Noto K, Sasaki M. Stereoselective Synthesis of 2,6-Cis-Substituted Tetrahydropyrans: Brønsted Acid-Catalyzed Intramolecular Oxa-Conjugate Cyclization of α,β-Unsaturated Ester Surrogates. J Org Chem 2011; 77:2588-607. [DOI: 10.1021/jo202179s] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Haruhiko Fuwa
- Graduate
School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577,
Japan
| | - Naoki Ichinokawa
- Graduate
School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577,
Japan
| | - Kenkichi Noto
- Graduate
School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577,
Japan
| | - Makoto Sasaki
- Graduate
School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577,
Japan
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A new strategy for the synthesis of substituted dihydropyrones and tetrahydropyrones via palladium-catalyzed coupling of thioesters. Tetrahedron 2011. [DOI: 10.1016/j.tet.2011.03.114] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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14
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Fuwa H, Noto K, Sasaki M. Biosynthesis-Inspired Intramolecular Oxa-Conjugate Cyclization of α,β-Unsaturated Thioesters: Stereoselective Synthesis of 2,6-cis-Substituted Tetrahydropyrans. Org Lett 2011; 13:1820-3. [DOI: 10.1021/ol200333p] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Haruhiko Fuwa
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Kenkichi Noto
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Makoto Sasaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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Fuwa H, Suzuki T, Kubo H, Yamori T, Sasaki M. Total synthesis and biological assessment of (-)-exiguolide and analogues. Chemistry 2011; 17:2678-88. [PMID: 21264972 DOI: 10.1002/chem.201003135] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Indexed: 11/06/2022]
Abstract
We describe herein an enantioselective total synthesis of (-)-exiguolide, the natural enantiomer. The methylene bis(tetrahydropyran) substructure was efficiently synthesized by exploiting olefin cross-metathesis for the assembly of readily available acyclic segments and intramolecular oxa-conjugate cyclization and reductive etherification for the formation of the tetrahydropyran rings. The 20-membered macrocyclic framework was constructed in an efficient manner by means of Julia-Kocienski coupling and Yamaguchi macrolactonization. Finally, the (E,Z,E)-triene side chain was introduced stereoselectively via Suzuki-Miyaura coupling to complete the total synthesis. Assessment of the growth inhibitory activity of synthetic (-)-exiguolide against a panel of human cancer cell lines elucidated for the first time that this natural product is an effective antiproliferative agent against the NCI-H460 human lung large cell carcinoma and the A549 human lung adenocarcinoma cell lines. Moreover, we have investigated structure-activity relationships of (-)-exiguolide, which elucidated that the C5-methoxycarbonylmethylidene group and the length of the side chain are important for the potent activity.
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Affiliation(s)
- Haruhiko Fuwa
- Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, Japan.
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Fuwa H, Yamaguchi H, Sasaki M. A Unified Total Synthesis of Aspergillides A and B. Org Lett 2010; 12:1848-51. [DOI: 10.1021/ol100463a] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Haruhiko Fuwa
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Hiroshi Yamaguchi
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Makoto Sasaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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Synthesis of six-membered oxygenated heterocycles through carbon–oxygen bond-forming reactions. Tetrahedron 2008. [DOI: 10.1016/j.tet.2007.11.092] [Citation(s) in RCA: 212] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Frein JD, Rovis T. Surveying approaches to the formation of carbon-carbon bonds between a pyran and an adjacent ring. Tetrahedron 2006; 62:4573-4583. [PMID: 17710219 PMCID: PMC1950123 DOI: 10.1016/j.tet.2006.02.042] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have examined several methods for the stereoselective formation of carbon-carbon bonds between contiguous rings where a stereogenic center is already present. The approaches investigated were a [1,3] oxygen to carbon rearrangement of cyclic vinyl acetals, an intermolecular enolsilane addition into an in situ generated oxocarbenium ion, an intramolecular conjugate addition of tethered alkoxy enones, and epimerization of several α-pyranyl cycloalkanones. These routes have been found to be complementary in several cases and have enabled formation of both the trans:anti and cis:anti stereoisomers in good to excellent yields and varying diastereoselectivities. We have proven C2-C2' relative stereochemistry of 1-2 via a chemical correlation.
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Affiliation(s)
- Jeffrey D. Frein
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
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Davies HML, Beckwith REJ. Catalytic Asymmetric Reactions for Organic Synthesis: The Combined C−H Activation/Siloxy-Cope Rearrangement. J Org Chem 2004; 69:9241-7. [PMID: 15609962 DOI: 10.1021/jo048429m] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Tetrakis(N-[4-dodecylbenzenesulfonyl]-(L)-prolinate) dirhodium [Rh(2)(S-DOSP)(4)]-catalyzed decomposition of vinyldiazoacetates in the presence of allyl silyl ethers results in the formation of the direct C-H insertion product and the product derived from a combined C-H activation/siloxy-Cope rearrangement. Both products are formed with very high diastereoselectivity (>94% de) and high enantioselectvity (78-93% ee). Under thermal or microwave conditions, the direct C-H insertion product undergoes a siloxy-Cope rearrangement in a stereoselective manner.
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Affiliation(s)
- Huw M L Davies
- Department of Chemistry, University at Buffalo, State University of New York, New York 14260-3000, USA.
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Schneider C, Reese O. Domino Michael Aldol and Domino Michael Mannich Reactions: Highly Stereoselective Synthesis of Functionalized Cyclohexanes This work has been supported by the Deutsche Forschungsgemeinschaft (Schn 441/1-2), the Fonds der Chemischen Industrie (doctoral fellowship to O. R.) and Degussa Hüls AG. We thank Prof. L. Tietze for constant support. Angew Chem Int Ed Engl 2000; 39:2948-2950. [PMID: 11028020 DOI: 10.1002/1521-3773(20000818)39:16<2948::aid-anie2948>3.0.co;2-p] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- C Schneider
- Institut für Organische Chemie der Universität Tammannstrasse 2, 37077 Göttingen (Germany)
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