Stereoselective Synthesis of α-Aminophosphonic Acids Using the Betti Base as Chiral Auxiliary

Abstract

A new diastereoselective synthesis of α-aminophosphonates has been developed, based on the reaction of trialkyl phosphites with a chiral imines, derived from (R)- or (S)-1-(α-aminobenzyl)-2-naphthol, in the presence of trifluoroacetic acid. The major diastereomer of obtained aminophosphonates can be separated by crystallization from an appropriate solvent. The desired α-aminophosphonic acids can be obtained in enantiopure form by treating the corresponding diastereomers with HCl.

Keywords:

• 1-(α-Aminobenzyl)-2-naphthol
• α-aminophosphonic acids
• asymmetric synthesis
• Betti base
• chiral auxiliary

Acknowledgments

This work was supported by the Civilian Research and Development Foundation (grant no. RUC2–2638-KA-05) and the Russian Foundation for Basic Research (grant no. 07-03-00617). The authors are grateful to Professor Ch. Е. McKenna and Dr. B. A. Kashemirov (University of Southern California) for collaboration.