Orthogonally Protected Sugar Diamino Acids as Building Blocks for Linear and Branched Oligosaccharide Mimetics

Abstract

Sugar amino acids (SAAs), which are carbohydrate derivatives with both an amino group and a carboxyl group connected to the carbohydrate frame, have found wide application as building blocks for oligosaccharide and peptide mimetics, as secondary-structure inducing elements, and as pharmacophore-presenting scaffolds for the generation of combinatorial libraries. Used as monomers with a rigid pyran ring, functional pharmacophoric groups attached to the hydroxy, amino, and carboxyl groups can be presented in a distinct spatial arrangement as was demonstrated in seminal studies by Hirschmann et al. Linear and cyclic oligomers of SAAs have been synthesized, taking advantage of well-established peptide chemistry, and in certain cases they adopt defined secondary structures. Sugar amino acids with an additional amino group, that is, sugar diamino acids, would be an attractive extension of this concept, giving access to novel branched oligomeric structures. However, their synthesis has not been reported until now. Here we introduce the protected derivatives 1 and 2 of 2,6-diamino-2,6-dideoxy-b-d-glucopyranosyl carboxylic acid,