Syntheses of model compounds related to an antigenic epitope in pectic polysaccharides from Bupleurum falcatum L.

Stereocontrolled syntheses of model compounds related to a category of the major antigenic epitope against anti-bupleurum 2IIc/PG-1-IgG from an anti-ulcer pectic polysaccharide are described. Glycosylation of the glucuronic acid donors methyl(2,3-di-O-benzoyl-4-O-methyl-alpha -D-glucopyranosyl trichloroacetimidate)uronate and methyl (2,3-di-O-benzoyl-4-O-methyl-beta -D-glucopyranosyl)uronate-(1 -->6)-2,3,4-tri-O-benzoyl-alpha -D-galactopyranosyl trichloroacetimidate with the common acceptor 2-(trimethylsilyl)ethyl 2,3,4-tri-O-benzyl-beta -D-galactopyranoside in the presence of trimethylsilyl triflate (TMSOTf) gave the desired di- and trisaccharide derivatives. Furthermore the products were transformed into the oligo-valent clustering saccharides, N,N',N"-tri-{5-[4-O-methyl-beta -D-glucopyranosyluronic acid-(1 --> 6)-beta -D-galactopyranosyloxy]pentylcarbonylaminoethyl}-1,3,5-benzenetriamide and N,N',N"-tri-{5-[4-O-methyl-beta -D-glucopyranosyluronic acid (1 --> 6)-beta -D-galactopyranosyl-(1 --> 6)-beta -D-galactopyranosyloxy]pentylcarbonylaminoethyl}-1,3,5-benzenetriamide. (C) 2001 Elsevier Science Ltd. All rights reserved.