Asymmetric synthesis of conformationally constrained L-AP4 analogues using chiral sulfinyl auxiliary

Constrained L-AP4 analogues, (2S,1′R,2′S)- and (2S,1′S,2′R)-2-(2′-phosphonocyclopropyl) glycines as well as their phenyl analogues (2S,1′S,2′R,3′S)-2-(2′-phosphono-3′-phenylcyclopropyl) glycine (PPCG-1) and (2S,1′R,2′S,3′R)-2-(2′-phosphono-3′-phenylcyclopropyl) glycine (PPCG-2) were synthesized. The stereogenic centers in cyclopropane ring were formed under sulfinyl group control, in asymmetric cyclopropanation of enantiomerically pure α-phosphoryl vinyl sulfoxides. The sulfinimine-mediated asymmetric Strecker reaction allowed to introduce amino acid moiety.