Stereoselective Synthesis of P-Chiral Phosphorus Compounds from N-tert-Butoxycarbonyl Amino Acids

Reaction of the N-t-Boc amino acids alanine and valine with PhPCl₂ gives the P-chiral trans-1,3,2-oxazaphospholidinones exclusively. Variable-temperature NMR and examination of the glycine derivative shows that the isomers observed are due to t-Boc rotation.