Asymmetric recognition of 1-arylethylamines by ( R)-phenylglycyl-( R)-phenylglycine and its mechanism

Abstract

An unprotected dipeptide, ( R)-phenylglycyl-( R)-phenylglycine, which is insoluble in water, was shown to be an excellent resolving reagent for racemic 1-arylethylamines. By simply stirring the mixture of the dipeptide and racemic 1-phenylethylamine in presence of water, asymmetric recognition occurred to give a salt of ( S)-1-phenylethylamine (95% ee) and the dipeptide. X-Ray crystallographic study of the salt elucidated the crystal structure of the diastereomeric salt, where hydrogen bonding and hydrophobic interaction between the dipeptide and amines play important roles in the construction of layers.