Direct access to new β-d-galactofuranoconjugates: application to the synthesis of galactofuranosyl-l-cysteine and l-serine

Galactofuranose post-translational modifications, although quite rare, were detected in some biomolecules produced by parasites. While hexopyranosides were already linked to various peptides and proteins, few hexofuranosides have been artificially conjugated to amino acids. We thus report herein a robust glycosylation methodology to obtain S-alkyl, O-serine and S-cysteine-β-d-galactofuranosides starting from readily available galactofuranose donors. O-Acetyl, thioimidoyl and acetimidoyl donors were compared in terms of yields and selectivity when reacted with mercaptans, l-cysteine and l-serine. Acetimidates turned out to be the best notably for amino acids glycosylation.