Synthesis of LacNAcLex‐ and DimLex‐BSA Conjugates and Binding to Anti‐Polymeric Lex mAbs

Abstract

The chemical synthesis of tetra‐ and pentasaccharide fragments of the tumor‐associated carbohydrate antigen dimeric Lewis X (dimLex) lacking either both or only the non‐reducing end fucosyl residues is described following a 1 + 1 + 1 synthetic strategy. Use of a 6‐chlorohexyl aglycon gave access to hexyl glycoside soluble inhibitors as well as the 6‐aminohexyl glycoside pentasaccharide. The 6‐aminohexyl glycoside pentasaccharide and a dimLex analogue were conjugated to BSA via a squarate linker and the glycoconjugates were shown by MALDI MS to both display an average of 16 oligosaccharides per BSA molecule. These glycoconjugates were used in the attempt to identify the smallest dimLex fragment required to maintain binding to mAbs SH2 and IG5F6, which are known to bind polymeric Lex structures preferentially over the monomeric Lex antigen. Titration studies showed that the non‐reducing end fucosyl residue in dimLex is involved in the recognition of the antigen by both mAbs SH2 and IG5F6.