A new synthesis of α-arbutin via Lewis acid catalyzed selective glycosylation of tetra-O-benzyl-α-d-glucopyranosyl trichloroacetimidate with hydroquinone

α-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 β-d-glucopyranoside). Enzymatic synthesis was preferred for α-arbutin previously, and now a new chemical synthesis is reported. The reaction of tetra-O-benzyl-α-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-α-d-glucopyranoside with high stereoselectivity and yield, and then to α-arbutin quantitatively after deprotection.