An enantioselective synthesis of differentially protected erythro-alpha,beta-diamino acids and its application to the synthesis of an analogue of rhodopeptin B5.

Methodology for the enantioselective synthesis of differentially protected erythro-alpha,beta-diamino acids from N-tosyloxy beta-lactams is reported. The requisite N-tosyloxy beta-lactams are readily available from simple beta-keto esters. The reported approach is flexible and compatible with a variety of functional groups. The synthetic utility of the method is demonstrated through its application to the preparation of an analogue of the antifungal cyclic peptide rhodopeptin B5.