Glycosylimidates, 54. Synthesis of the GlcNAcβ(1→4)MurNAcβ(1→4)GlcNAcβ(1→4)MurNAc tetrasaccharide of bacterial peptidoglycan

From 2‐azido‐2‐deoxy‐ D ‐glucose have been prepared at 1‐O and/or 4‐O selectively protected glucosamine and muramic acid derivatives, which were transformed into glycosyl donors 6 and 14a, b and into glycosyl acceptors 7 and 15 . The reaction of these donors and acceptors yielded disaccharides 8 and 11–13 . Selective 1a‐ O ‐deprotection of disaccharide 12 and subsequent treatment with trichloroacetonitrile afforded disaccharide donor 17 ; selective removal of the 4b‐ O ‐protective groups in disaccharides 8 and 11 furnished disaccharide acceptor 9 . These building blocks were employed in the synthesis of β‐connected tetrasaccharide 18 which gave upon azido group reduction, acetylation of the amino groups, and complete O ‐deprotection the desired target molecule 1 characterized as its fully O ‐acetylated product 2 .