Dynamic kinetic resolution of 2-phenylpropanal derivatives to yield β-chiral primary amines via bioamination

The amination of racemic α-chiral aldehydes, 2-phenylpropanal derivatives, was investigated employing ω-transaminases. By medium and substrate engineering the optical purity of the resulting β-chiral chiral amine could be enhanced to reach optical purities up to 99% ee. Using enantiocomplementary ω-transaminases allowed us to access the (R)- as well as the (S)-enantiomer in most cases. It is important to note that the stereopreference of the ω-transaminases found for α-chiral aldehydes did not correlate with the stereopreference previously observed for the amination of methyl ketones. In one case the stereopreference switched even upon exchanging a methyl substituent to a methoxy group.