Synthesis of N-Protected (beta)-Aminocyclopropanedicarboxylates and Their Ring Transformation to N-Benzhydryl-3-alkoxycarbonyl-4,4dialkylpyrrolidin-2-ones

An easy and short synthesis of new N-protected (beta)aminocyclopropanedicarboxylates, a rather unexplored class of highly activated conformationally constrained (beta)-amino acid derivatives, is described. Michael-induced ring closure (MIRC) of diphenylmethylidenamine to 2-bromoalkylidenemalonates leads to 3,3dialkyl-2-(diphenylmethylidenamino)cyclopropane-1,1-dicarboxylates, the reactivity of which with hydrides was investigated, yielding 3(alkoxycarbonyl)pyrrolidin-2-ones.