Synthesis of Pentasaccharide Fragments Related to the O‐Specific Polysaccharide of Shigella flexneri Serotype 1a

Abstract

AbstractThe synthesis of the pentasaccharide 5‐aminopentylglycosides α‐L‐Rhap‐(1→3)‐[α‐D‐Glcp‐(1→4)]‐β‐D‐GlcpNAc‐(1→2)‐α‐L‐Rhap‐(1→2)‐α‐L‐Rhap‐1‐O‐(CH2)5NH2 (29) andα‐L‐Rhap‐(1→3)‐α‐L‐Rhap‐(1→3)‐[α‐D‐Glcp‐(1→4)]‐β‐D‐GlcpNAc‐(1→2)‐α‐L‐Rhap‐1‐O‐(CH2)5NH2 (28), related to the O‐specific polysaccharide of Shigella flexneri serotype 1a by coupling of the suitably protected trisaccharides α‐D‐Glcp‐(1→4)‐β‐D‐Glcp(1→2)‐α‐L‐Rhap‐1‐O‐(CH2)5NH2 (23) and α‐L‐Rhap‐(1→3)‐[α‐D‐Glcp‐(1→4)]‐β‐D‐Glcp‐1‐SPh (26) with the corresponding rhamnosyl glycosides α‐L‐Rhap‐(1→3)‐α‐L‐Rhap‐1‐SEt (17) and α‐L‐Rhap‐(1→3)‐α‐L‐Rhap‐1‐O‐(CH2)5NH2 (13), is described. Building blocks 23 and 26 were prepared by intramolecular glycosylation of an unsymmetrically tethered cellobiosamine derivative. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)