SIMPLE SYNTHESIS OF BETA-D-GLUCOSYL ESTERS

Acylation of 2,3,4,6-tetra-0-benzyl-alpha-D-glucopyranose (1) with benzoyl chloride and triethylamine was found to give 1-O-benzoyl-2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranose (2) and 1-O-benzoyl-2,3,4,6-tetra-O-benzyl-beta-D-glucopyranose (3) in a ratio of 2:9 while acylation of 1 with benzoyl chloride and pyridine gave 2 and 3 in the ratio 6: 1. Slow addition of benzoyl chloride to 1 and triethylamine changed the ratio from 2:9 to 1 : 11. Similar acylation of 1 with either 2- or 4-chlorobenzoyl, acetyl or butanoyl chloride gave the corresponding 1-O-acyl-derivatives 4, 5, 6 or 7 with high predominance of the beta-anomer. The rate of addition had to be decreased for the aliphatic acyl chlorides to provide good stereoselectivity. 3, 5, 6 and 7 was hydrogenolyzed to give 1-O-benzoyl, 1-O-4-chlorobenzoyl, 1-O-acetyl and 1-O-butanoyl-beta-D-glucopyranoses 8, 9, 10 and 11, respectively.