A sulfur-involved ligation for thioamide
quasi-peptides was developed
via amino acids and amino aldehydes coupling. The key to the transformation
was the chelation of copper with imines for chiral activation and
fixation. In this environment, linear polysulfur decreased the alkalinity
of single sulfur anions to prevent racemization caused by the interaction
between sulfur and sodium sulfide. Dipeptides, tripeptides, tetrapeptides,
and the linkage between the drug and amino acids were successfully
obtained