Polyannulated glycopyranosides via radical-mediated tandem reactions. Stereoselective synthesis of 6 center dot 5 center dot 6 dioxatricycles via 5-exo-trig, 6-endo-dig mode .3.

被引:17
作者
Hoffmann, HMR
Herden, U
Breithor, M
Rhode, O
机构
[1] Department of Organic Chemistry, University of Hannover
关键词
D O I
10.1016/S0040-4020(97)00518-8
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
A series of C-silylated enynols, e.g. 6-methyl-1-trimethylsilyl-hept-5-en-1-yn-4-ol (rac-A) was prepared and submitted to N-iodosuccinimide mediated iodoalkoxylation of tri-O-acetylglycal. Thanks to the presence of the silyl group the resulting diastereomeric glycosides (S)A(1) and (R)A(1) were readily separated. Triethylborane/oxygen/ethyl iodide promoted iodine transfer afforded doubly annulated glycosides in a 5-eso-trigonal, 6-endo-digonal cascade. The required re-protection of the three acetoxy groups was carried out orthogonally The newly installed iodocyclohexene moiety served as site for further functionalization, which was accomplished by metal-halogen exchange followed by electrophilic capture or by reduction/epoxidation. (C) 1997 Elsevier Science Ltd.
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页码:8383 / 8400
页数:18
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