Synthesis of α-d-GlcpNAc-(1→2)-[α-d-ManpNAc-(1→3)-]α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-α-l-Rhap, the repeating unit of O10 antigen from Acinetobacter baumannii

An efficient synthesis of α-d-GlcpNAc-(1 → 2)-[α-d-ManpNAc-(1 → 3)-]α-l-Rhap-(1 → 2)-α-l-Rhap-(1 → 3)-α-l-Rhap (1), the repeating unit of the O10 antigen from Acinetobacter baumannii was achieved via sequential assembly of the building blocks, p-methoxylphenyl 2,4-di-O-benzoyl-α-l-rhamnopyranoside (2); 2-O-allyloxycarbonyl-3,4-di-O-benzoyl-α-l-rhamnopyranosyl trichloroacetimidate (3); 4-methoxylphenyl 3-O-allyloxycarbonyl-4-O-benzoyl-α-l-rhamnopyranoside (4); 2-azido-3-O-benzoyl-2-deoxy-4,6-O-isopropylidene-α-d-mannopyranosyl trichloroacetimidate (5); 2-azido-3,4,6-tri-O-benzoyl-2-deoxy-α,β-d-glucopyrano syl trichloroacetimidate (6). The total yield of 1 from 4 was 4.7%.