Septanose carbohydrates. VII. Preparation of mono-O-isopropylidene derivatives of methyl #beta#-D-glucoseptanoside and preparation of methyl #alpha#- L-idoseptanoside and its derivatives

摘要

Three mono-O-isopropylidene derivatives of methyl #beta#-D-glucoseptanoside have been prepared by acid-catalysed hydrolysis of methyl 2,3:4,5-di-O-isopropylidene-#beta#-D-glucoseptanoside or by acetonation of methyl #beta#-D-glucoseptanoside. Two of these derivatives have been used for the preparation of methyl 2,3-O-isopropylidene-#alpha#-L-idoseptanoside (8a) and methyl 3,4-O-isopropylidene-#alpha#-L-idoseptanoside (10a). Hydrolysis of (10a) yielded methyl #alpha#-L-idoseptanoside (12a) and acetonation of (8a) and (12a) yielded methyl 2,3:4,5-di-O-isopropylidene-#alpha#-L-idoseptanoside. Possible conformations of these compounds are discussed.