Stereoselective single-step synthesis and X-ray crystallographic investigation of acetylated aryl 1,2-trans glycopyranosides and aryl 1,2-cis C2-hydroxy-glycopyranosides.

Reported is an attractive and environmentally friendly method for the synthesis of the title compounds in moderate yield using inexpensive 1,2,3,4,6-penta-O-acetyl-beta-D-gluco- and galactopyranoses as sugar donors, five different phenols as acceptors and H-beta zeolite as the catalyst. The yield (23-28%) of aryl 3,4,6-tri-O-acetyl-alpha-D-glycopyranosides obtained in this single-step procedure is considerably higher than that obtained using previously reported methods. Treatment of an orthoacetate, 3,4,6-tri-O-acetyl-[1,2-O-(1-p-fluorophenoxyethylidene)]-alpha-D-glucopyranose, with p-fluorophenol under the same solvent-free reaction conditions also led to the formation of the title compounds in similar yield and composition. X-ray crystallographic analysis of phenyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranoside and p-fluorophenyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranoside showed that the molecular packing is stabilized by C-H...O, C-H...pi and C-H...F interactions, in addition to regular hydrogen bonding patterns.