The tetrasaccharide repeating unit of Escherichia coli O9a, α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Manp-(1→3)-D-Manp, and the pentasaccharide repeating unit of E. coli O9 and Klebsiella O3, α-D-Manp-(1→2)-α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Manp-(1→3)-D-Manp, were synthesized as their methyl methyl glycosides. Thus, selective 3-O-allylation of p-methoxyphenyl a-Dmannopyranoside via a dibutyltin intermediate gave p-methoxyphenyl 3-O-allyl-a-D-mannopyranoside (2) in good yield. Benzoylation (→3), then removal of 1-O-methoxyphenyl (→4), and subsequent trichloroacetimidation afforded the 3-O-allyl-2,4,6-tri-O-benzoyl-a-D-mannopyranosyl trichloroacetimidate (5). Condensation of 5 with methyl 4,6-O-benzylidene-a-Dmannopyranoside (6) selectively afforded the (1→3)-linked disaccharide 7. Benzoylation of 7, debenzylidenation, benzoylation, and deallylation gave methyl 2,4,6-tri-O-benzoyl-a-D-mannopyranosyl-(1→3)-2,4,6-tri-O-benzoyl-a-D-mannopyranoside (11) as the disaccharide acceptor. Coupling of 11 with (1→2)-linked mannose disaccharide donor 17 or trisaccharide donor 21, followed by deacylation, furnished the target tetrasaccharide and pentasaccharide, respectively.
oligosaccharide, Mannose, Regioselective synthesis
NCBI PubMed ID: 11861011Publication DOI: 10.1016/S0008-6215(02)00011-3Journal NLM ID: 0043535Publisher: Elsevier
Correspondence: fzkong@mail.rcees.ac.cn
Institutions: Research Center for Eco-Environmental Sciences, Academia Sinica, PO Box 2871, Beijing 100085, PR China
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