Synthesis of “Mixed Type” Oligosaccharide Mimetics Based on a Carbohydrate Scaffold

Abstract

In multivalent glycoligands including cluster glycosides, one type of sugar epitope is normally clustered. Such molecules have been valuable tools for investigation and inhibition of cell adhesion processes. They have, for example, served as in vitro antiadhesives in mannose-specific bacterial adhesion. Wild-type bacteria, however, utilize a number of different sugar epitopes for adhesion, involving bacterial lectins of different specificity. The synthesis of glycomimetics containing sugar derivatives from different sugar series is therefore of interest, with the eventual goal of providing multivalent glycoligands of a more complex type. The synthesis of novel “mixed” glycoclusters, starting from the trifunctional galactoside 10 that serves as a carbohydrate scaffold, is hence presented here. Compound 10 has three potential reactive sites, which were addressed successively. Firstly, peptide coupling with the carboxy-functionalized mannoside 11 furnished the disaccharide mimetic 13, which in turn provided the trisaccharide mimetic 19 after peptide coupling with the amino-functionalized fucoside 17. Finally, a pentasaccharide mimetic 23 was obtained after thiourea-bridging with acetylated lactosyl isothiocyanate.