Chemoenzymatic Synthesis of Naturally Occurring Benzyl 6-O-Glycosyl-β-D-glucopyranosides

Abstract

Direct β-glucosidation between benzyl alcohol and D-glucose (5) using the immobilized β-glucosidase from almonds with the synthetic prepolymer ENTP-4000 gave a benzyl β-D-glucoside (1) in 53% yield. The coupling of the benzyl β-D-glucopyranoside congener (8) derived from 1 with phenyl 2,3,4-tri-O-acetyl-1-thio-β-D-xylopyranoside (9), ethyl 2,3,4-tri-O-acetyl-1-thio-α-L-rhamnopyranoside (13), and 2,3,4-tri-O-acetyl-α-L-arabinopyranosyl bromide (15) afforded 10, 14, and 16, respectively, as coupled products. Deprotection of 10, 14, and 16 provided the synthetic benzyl β-D-xylopyranosyl-(1→6)-β-D-glucopyranoside (2), benzyl α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside (3), and benzyl α-L-arabinopyranosyl-(1→6)-β-D-glucopyranoside (4), respectively.