A facile Cu(I)/TF-BiphamPhos-catalyzed asymmetric approach to unnatural α-amino acid derivatives containing gem-bisphosphonates.

A novel catalytic asymmetric Michael addition of azomethine ylide with β-substituted alkylidene bisphosphates was realized in the presence of a chiral copper(I)/TF-BiphamPhos complex. The present system provides a unique and facile access to enantioenriched unnatural α-amino acid derivatives containing gem-bisphosphonates (gem-BPs) in high yields with excellent diastereoselectivities and enantioselectivities. Subsequent transformations lead to the expedient preparation of biologically active unnatural α-amino acid derivatives containing BPs and bisphosphonic acids without loss of diastereo- and enantiomeric excess.