Enaminosucres et sucres halogénoacétyléniques . Communication préliminaire

Enamino‐ and Halogenoacetylenic sugars Traitment of an aldehydosugar ( 1 ) with secondary amines gave in an essentially quantitative yield the expected enamines ( 4–6 ). Chloro‐ and bromo‐acetylenic sugars ( 11–14 ) were obtained in good yields by reacting with lithium methylphenylamide the corresponding gem ‐dihalo‐olefinic sugars ( 7–10 ), whereas a Z‐gem ‐fluoro‐enamine ( 17 ) was formed when the difluoro‐olefinic sugar 15 was submitted to the same reaction. The fluoro‐enamine 17 is a useful synthetic intermediate allowing the preparation of several kinds of C ‐glycosylic compounds bearing heterocycles like isoxazole, chromone or coumarin.