Catalytic enantioselective synthesis of cyclopropyl α-amino carboxylates and phosphonates

Abstract

Herein, the catalytic asymmetric synthesis of cyclopropyl α-amino carboxylates is reported. Using a chiral rhodium complex (Rh₂((R)-BTPCP)₄), the synthesis of a large panel of non-canonical α-amino carboxylates bearing a cyclopropyl ring was obtained in high yields (17 examples, from 20% to 97% yield), as single diastereoisomers and excellent enantiomeric ratio (from 72 : 28 to 99.5 : 0.5 er). The method was extended to the synthesis of the unprecedented cyclopropyl α-amino phosphonates, by changing the catalyst (Rh₂((R)-p-PhTPCP)₄). The cyclopropanes were obtained in moderate to high yields (18 examples, from 41% to 89% yield), with excellent enantiomeric ratio (from 56.5 : 43.5 to 99 : 1 er) and as single diastereoisomers. Finally, the synthetic utility of these α-amino carboxylates was illustrated through several post-functionalizations.