A practical synthesis of β-D-GlcA-(1→3)-β-D-Gal-(1→3)-β-D-Gal-(1→4)-D-Xyl, a part of the common linkage region of a glycosaminoglycan

A practical synthesis of beta-D-GlcA-(1 --> 3)-beta-D-Gal-(1 --> 3)-beta-D-Gal-(1 -->4)-beta-D-Xyl-(1 --> OMe) was achieved by coupling of methyl 2,3,4-tri-O-acetyl-alpha-D-glucopyranosyluronate trichloroacetimidate with a trisaccharide acceptor. The trisaccharide acceptor was obtained by condensation of 3-O-allyl-2,4,6-tri-O-benzoyl-beta-D-galactopyranosyl-(1 --> 3)-2,4,6-tri-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate with methyl 2,3-di-O-benzoyl-beta-D-xylopyranoside, followed by deallylation. The beta-(1 --> 3)-linked disaccharide was prepared readily with p-methoxyphenyl 3-O-allyl-2,4,6-tri-O-benzoyl-beta-D-galactopyranoside as the key synthon. The alpha-(1--> 3)-linkage was formed in considerable amount with galactose mono- and disaccharide trichloroacetimidate donors with C-2 neighboring group participation. CO 2002 Elsevier Science Ltd. All rights reserved.