Patent ID: 8148505

Claim:
An α-selective glycosylation process between a donor compound having a sugar structure and an acceptor compound having an alcoholic hydroxyl group or thiol group comprising, (1) the step of providing a sugar structure of hexose or an aldose having a chain with six carbon atoms in the molecule which is a monosaccharide or a reducing end of an oligosaccharide having two or more monosaccharide residues or a sugar chain, which sugar structure satisfies the constitutional conditions such that the sugar structure has hydroxyl groups at positions 4 and 6 and that the hydroxyl group at position 4 is in an axial bond and a group at position 5 is in equatorial bond, wherein the sugar structure is substituted with amino at position 2, the amino being bound to a 2,2,2-trichloroethoxycarbonyl group, the sugar structure having a hydroxyl group at the 3-position that is protected with a group selected from among an acetyl group, a benzoyl group, a pivaloyl group, a benzyl group, a p-methoxybenzyl group and an allyl group, (2) a step of forming a protective group in a silyl acetal structure in a ring shape over the hydroxyl groups at positions 4 and 6 in the sugar structure, and (3) a step of promoting the glycosylation between the sugar structure and the alcoholic hydroxyl groups or thiol group of the acceptor compound, and (4) a step of preparing a sugar structure glycoside containing α-glycoside at a ratio of 80% or more in the ratio of α-/β-glycosides, wherein the acceptor compound is selected from the group consisting of serine, threonine, cystine, peptides, mono or oligogalactopyranosides, and mono or oligoglucopyranosides.