Stereoselective CC bond formation in carbohydrates by radical cyclization reactions-III. Strategy for the preparation of C(1)-glycosides

✍ Scribed by Alain De Mesmaeker; Pascale Hoffmann; Beat Ernst; Paul Hug; Tammo Winkler

• Publisher: Elsevier Science
• Year: 1989
• Tongue: French
• Weight: 207 KB
• Volume: 30
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)93879-1

✦ Synopsis

A new strategy for the stereoselective synthesis of cz-and 13-C(1)-glycosides based on an intramolecular radical cyclization reaction is described. Intramolecular hydrogen atom transfer was observed depending on the concentration of the reagents, the conformation and the substitution of the cyclized radical.

Intensive work has been devoted to the synthesis of C-branched sugars t~). Among the methods available for the preparation of C(1)-glycosides, the intermolecular addition of glycopyranosidic radicals to olefins has been shown to be very useful 3). We propose here a new strategy (scheme 1) for the stereoselective C-C bond formation at the anomeric position of carbohydrates based on an intramolecular radical cyclization reaction offering three major advantages in comparison with the intermolecular processes: a) more efficient C-C bond formation, b) higher stereoselectivity due to the exclusive formation of a cis ring junction, c) access to both ct-