Facile synthesis of 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4,6-tetra-O-acetyl-d-glycopyranosyl)-α-d-glucopyrano]-[2′,1′,4,5]- 2-oxazolines, key intermediates for the synthesis of oligosaccharides

A simple synthesis of disaccharide oxazolines has been developed. Condensation of methyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-d-glucopyranoside with 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide, followed by removal of the 4,6-O-benzylidene group from the resulting disaccharide derivative, gave crystalline methyl 2-acetamido-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-glucopyranoside which, on acetolysis with acetic anhydride-acetic acid-sulfuric acid, provided 2-methyl-[4,6-di-O-acetyl-1,2-dideoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-glucopyranol]- [2′,1′,4,5]-2-oxazoline (7). Synthesis of the related α-d-mannopyranosyl compound was similarly accomplished. The glycosylating capability of 7 was employed for the synthesis of 6-(benzyloxycarbonylamino)hexyl 2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-β-d-glucopyranoside (18). An alternative synthesis of compound 18 is also described.