Efficient synthesis of 3,6-dideoxy-beta-D-arabino-hexopyranosyl-terminatedLacdiNac glycan chains of the Trichinella spiralis parasite

The synthesis of a linear trisaccharide epitope of the Trichinella spiralis N-linked glycan, in a form amenable to glycoconjugate formation, is report ed. The trisaccharide contains the synthetically challenging LacdiNAc [beta -GalpNAc(1-->4)-beta-GlcpNAc] element, as well as a terminal 3,6-dideoxy-be ta-D-arabino-hexopyranose (tyvelose) residue. An orthogonal protection stra tegy is described, which permits the protection and manipulation of three a mino groups present in the disaccharide beta-GalNAc(1-->4)-beta-GlcNAc and the tether used to prepare neoglycoconjugates. The beta-linked dideoxyhexos e was generated in excellent yield by the introduction of the dideoxyhexose unit as a beta-D-ribo-hexopyranoside (paratose) followed by an oxidation-r eduction sequence to generate the beta-D-arabino configuration in high dias tereomeric excess. The required dideoxyhexose donor was synthesized in a se ries of high-yielding steps from glucose utilizing the p-methoxyphenyl glyc oside.