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Total Synthesis of (+)-Dactylolide. Studies on the Cascade Cyclization Reactions of Epoxides/Polyepoxides Initiated by Single Electron Transfer

Wan, Shuangyi (2008) Total Synthesis of (+)-Dactylolide. Studies on the Cascade Cyclization Reactions of Epoxides/Polyepoxides Initiated by Single Electron Transfer. Master's Thesis, University of Pittsburgh. (Unpublished)

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The total synthesis of the marine macrolactone (+)-dactylolide was achieved in a highly convergent and efficient way (Scheme I). The route involves the coupling of two functionalized fragments of the molecule, an ¦Á,¦Â-unsaturated aldehyde and a 1,3-syn-diol, to form a cyclic ¦Á,¦Â-unsaturated cyclic acetal. Both enantiopure fragments arise from asymmetric vinylogous Mukaiyama aldol reactions. The key transformations in this synthesis include a sequential Peterson olefination/Prins cyclization reaction to construct the 2,6-cis-disubstituted-4-methylenetetrahydropyran core efficiently and stereoselectively, a Mislow-Evans selenoxide-selenate [2,3] sigmatropic rearrangement to transpose allylic alcohol transposition and an intramolecular Horner-Emmons macrocyclization.A systematic study on the cascade cyclizations of epoxides/polyepoxides initiated by single electron transfer has been carried out (Scheme II). Four monoepoxides and six diepoxides were tested. The results showed that the bicyclo[3.1.0] epoxonium ion intermediates formed in the cyclization favor 5-exo-cyclization in the nonpolar solvent (1,2-dichloroethane) while in the polar solvent (CH3CN), they prefer 6-endo-selectivity. However, the bicyclo[4.1.0] epoxonium ion intermediates usually give 7-endo regiochemical selectivity in the presence of substitution-induced bias. However, without the substituent effect, 6-exo and 7-endo-cyclizations are two competitive pathways.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Wan, Shuangyishw5@pitt.eduSHW5
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairFloreancig, Paul E
Committee MemberBrummond, Kay M
Committee MemberKoide, Kazunori
Date: 17 January 2008
Date Type: Completion
Defense Date: 17 January 2006
Approval Date: 17 January 2008
Submission Date: 4 October 2007
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: cascade cyclization; epoxide; total synthesis
Other ID:, etd-10042007-173306
Date Deposited: 10 Nov 2011 20:02
Last Modified: 15 Nov 2016 13:50


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