Synthesis of C-glycosides via radical cyclization reactions with a vinylsilyl tether. Control of the reaction course by a change in the conformation of the pyranose ring due to steric repulsion between adjacent bulky protecting groups

Tetrahedron Letters

Volumn 40, Issue 30, 1999, Pages 5527-5531

  Yahiro, Yumi ^a   Ichikawa, Satoshi ^a   Shuto, Satoshi ^a   Matsuda, Akira ^a  

^a HOKKAIDO UNIVERSITY   (Japan)

Author keywords

Conformation; Glycosidation; Glycosides; Radical reactions; Radicals

Indexed keywords

GLYCOSIDE; SILANE DERIVATIVE; VINYL DERIVATIVE;

ARTICLE; CHEMICAL ANALYSIS; CHEMICAL REACTION; CYCLIZATION; DRUG CONFORMATION; DRUG SYNTHESIS; STEREOCHEMISTRY; STRUCTURE ANALYSIS;

EID: 0033166698     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(99)01026-6     Document Type: Article

References (20)

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10. Synthesis of C-glycosides via radical cyclizations with a (2-phenylethynyl)silyl tether has been reported: Stork, G.; Suh, H. S.; Kim, G. J. Am. Chem. Soc. 1991, 113, 7054-7055.
11. Synthesis of C-glycosides via radical cyclizations with allyl tethers has been reported: De Mesmaeker, A.; Waldner, A.; Hoffmann, P.; Winkler, T. Synlett 1994, 330-332 and references cited therein.
12. 3N (4.0 equiv.) in toluene at room temperature.
13. Each of the compounds was purified by C18 HPLC.
14. The results on 7D-S and 7D-R, and 8D suggested that 5-hydrogen abstraction proceeded mainly via the 1′S-exocyclized intermediate. The 1′-stereochemistries of (1′S)-7 and (1′R)-7 were confirmed by NOE experiments, after 7 (a diastereomeric mixture at the 1′-position) was converted into the corresponding 2,1′-O-isopropylidene derivatives where the 1′S-and 1′R-isomers were successfully separated.
15. 4,5=9.4, which suggested that all of the ring protons were in axial positions.
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17. 4-conformation by X-ray crystallographic analysis: Walford, C.; Jackson, R. F. W.; Rees, N. H.; Clegg, W.; Heath, S. L. Chem. Commun. 1997, 1855-1856.
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20. 4,5=ca. 0, which suggested that H-2, -3, -4, and -5 were in equatorial positions.