Synthesis of a fully protected glycooctaosyl serine isolated from blood group A human ovarian mucin.

N-(9-Fluorenylmethoxycarbonyl)-O-([O-(2-acetamido-3,4,6-tri-O-acet yl-2- deoxy-alpha-D-galactopyranosyl)-(1-->3)-O-[(2,3,4-tri-O-benzyl-alpha-L- fucopyranosyl)-(1-->2)]-O-(4,6-di-O-acetyl-beta-D-galactopyranosyl)- (1-->3)-O-(3,6-di-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)- (1-->6)]-O-[(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-alpha-D- galactopyranosyl)-(1-->3)-O-[(2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl)- (1-->2)]-O-(4,6-di-O-acetyl-beta-D-galactopyranosyl)-(1-->3)]-2- acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1-->3)-L-serine allyl ester, a protected glycosylserine identified as a blood group A mucin-type determinant, was synthesized for the first time in an efficient and stereocontrolled manner. Ethyl O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy- alpha-D-galactopyranosyl-(1-->3)-O-[(2,3,4-tri-O-benzyl-alpha-L- fucopyranosyl)-(1-->2)]-O-(4,6-di-O-acetyl-beta-D-galactopyranosyl)- (1-->3)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-1-thio-beta-D-glucopyranos ide and N-(9-fluorenylmethoxycarbonyl)-O-[O-(2-acetamido-3,4,6-tri-O-acety l-2- deoxy-alpha-D-galactopyranosyl)-(1-->3)-O-[(2,3,4-tri-O-benzyl-alpha-L- fucopyranosyl)-(1-->2)]-O-(4,6-di-O-acetyl-beta-D-galactopyranosyl)- (1-->3)-2-acetamido-2-deoxy-alpha-D-galactopyranosyl]-(1-->3)-L-serine allyl ester were the key intermediates for the crucial glycosylation to afford the title compound.