ABSTRACT
Enzymatic transamination is catalyzed by pyridoxal/pyridoxamine, and it involves remarkable cooperative catalysis of a Lys residue in the transaminase. Inspired by transaminases, we developed a class of axially chiral pyridoxamines 11 bearing a lateral amine arm. The pyridoxamines exhibited high catalytic activity and excellent enantioselectivity in asymmetric transamination of α-keto acids, to give various α-amino acids in 67-99% yields with 83-94% ee's. The lateral amine arm likely participates in cooperative catalysis as the Lys residue does in biological transamination and has an important impact on the transamination in terms of activity and enantioselectivity.
ABSTRACT
A series of chiral pyridoxals 8 and 9 have been developed from commercially available pyridoxine and (S)-α,α-diarylprolinols. The pyridoxals exhibited good catalytic activity in an asymmetric transamination of α-keto acids with 2,2-diphenylglycine (7f) as the amine source to give various α-amino acids in 29-85% yields with 53-80% ee's. The current asymmetric transamination has successfully mimicked a complete biological transamination process characterized by two half-transaminations, a small chiral pyridoxal molecule acting as the catalyst, and enantioselective control.
