Diethyl Phosphite Initiated Coupling of α‑Ketoesters with Imines for Synthesis of α‑Phosphonyloxy-β-amino Acid Derivatives and Aziridine-2-carboxylates

Coupling of α-ketoesters
with imines initiated by diethyl
phosphite in the presence of alkaline metal hexamethyl­disilazides
is reported. Base-promoted addition of diethyl phosphite to α-ketoesters,
followed by [1,2]-phosphonate/phosphate rearrangement, generates α-phosphonyloxy
enolates that are subsequently intercepted by imines. The use of suitable
azomethine coupling partners allows selective construction of syn-α-hydroxy-β-amino acid derivatives or trans-aziridine-2-carboxylates in high yields with excellent
diastereoselectivities.