A new synthesis of alpha-arbutin via Lewis acid catalyzed selective glycosylation of tetra-O-benzyl-alpha-D-glucopyranosyl trichloroacetimidate with hydroquinone.

alpha-Arbutin has huge application potentials in the cosmetic industry, as its inhibitory effect on human tyrosinase is stronger than that of its naturally occurring anomer arbutin (4-hydroxyphenyl beta-D-glucopyranoside). Enzymatic synthesis was preferred for alpha-arbutin previously, and now a new chemical synthesis is reported. The reaction of tetra-O-benzyl-alpha-D-glucopyranosyl trichloroacetimidate, as glycosyl donor, with hydroquinone was initiated by catalytic amounts of trimethylsilyl trifluoromethanesulfonate (TMSOTf), resulting in 4-hydroxyphenyl 2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranoside with high stereoselectivity and yield, and then to alpha-arbutin quantitatively after deprotection.