1‐(α‐Aminobenzyl)‐2‐naphthol: A New Chiral Auxiliary for the Synthesis of Enantiopure α‐Aminophosphonic Acids

Abstract

Abstract Ooh Betti! A new diastereoselective synthesis of α‐aminophosphonates has been developed based on the reaction of trialkyl phosphites with chiral imines derived from ( R )‐ or ( S )‐1‐(α‐aminobenzyl)‐2‐naphthol (Betti base; see scheme, X=H, CH 3 , or Br). The reaction proceeds with high diastereoselectivity. Treatment with HCl results in the formation of the desired α‐aminophosphonic acids. magnified image A new diastereoselective synthesis of α‐aminophosphonates has been developed, based on the reaction, in the presence of trifluoroacetic acid, of trialkyl phosphites with chiral imines derived from ( R )‐ or ( S )‐1‐(α‐aminobenzyl)‐2‐naphthol. The reaction proceeds at room temperature in toluene with high diastereoselectivity. The major diastereomer can be separated by crystallization from an appropriate solvent. The relative configuration of both chiral centers of the major diastereomer was determined by single‐crystal X‐ray structure analysis. The desired α‐aminophosphonic acids can be obtained in enantiopure form by treatment of the corresponding diastereomers with HCl.