A New Versatile and Diastereoselective Synthesis of Polysubstituted 2-Oxopiperazines from Naturally Occurring Amino Acids

A highly stereoselective approach to 1,3,4,5- and 1,3,30,4,5-polysubstituted 2-oxopiperazines is reported. The method is based on the synthetic elaboration of naturally occurring amino acids to obtain enantiomerically enriched C-5 substituted oxopiperazines, which are further functionalized at C-3 via enolate formation and reaction with electrophiles. Notably, the two nitrogens of the ring can be orthogonally protected.