Synthesis of enantiopure vicinal diaminoesters and ketopiperazines from N-sulfinylimidazolidines

A short and efficient synthesis of mono- and bicyclic ketopiperazines bearing methoxycarbonyl substituents is described. The route entails selective protection and solvolysis of N-sulfinylimidazolidines to provide vicinal diaminoesters with the nitrogen atoms suitably differentiated. Then, an N-acylation/cyclization protocol renders the ketopiperazines. In addition a diastereoselective route to an analog of the natural diketopiperazine DKP 593A through a 2-piperidinylglycinate available by this method is described.