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 (18 examples, from 20% to 97% yield), as single diastereoisomers and excellent enantiomeric ratio (from 63:37 to 99.5:0.5 e.r.). 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 96% yield), with excellent enantiomeric ratio (from 56.5:43.5 to 99:1 e.r.) and as single diastereoisomers. Finally, the synthetic utility of these α-amino carboxylates was illustrated through several post-functionalizations.