S‑Michael Additions to Chiral Dehydroalanines as an Entry to Glycosylated Cysteines and a Sulfa-Tn Antigen Mimic

Stereoselective sulfa-Michael addition of appropriately protected thiocarbohydrates to chiral dehydroalanines has been developed as a key step in the synthesis of biologically important cysteine derivatives, such as S-(β-d-glucopyranosyl)-d-cysteine, which has not been synthesized to date, and S-(2-acetamido-2-deoxy-α-d-galactopyranosyl)-l-cysteine, which could be considered as a mimic of Tn antigen. The corresponding diamide derivative was also synthesized and analyzed from a conformational viewpoint, and its bound state with a lectin was studied.