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.
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.
Vitamin B6 serves as universal co‐enzymes in biological systems. However, its catalytic power has not been applied into the area of asymmetric catalysis. Based on the core structure of vitamin B6, we have developed several types of pyridoxal and pyridoxamine catalysts with different structural skeletons and different electronic properties. With these pyridoxals and pyridoxamines as catalysts, we have realized biomimetic asymmetric transamination of α‐keto acids and biomimetic asymmetric Mannich reaction of glycinate, respectively, to give various chiral α‐amino acids and α,β‐diamino acids in good yields with excellent diastero‐ and/or enantioselectivities. Both of the reactions have perfectly mimicked the corresponding biological transformations.
The inside cover picture shows the development of chiral pyridoxal and pyridoxamine catalysts by mimicking vitamin B6‐dependent enzymes. These chiral pyridoxals and pyridoxamines displayed extraordinary catalytic performances in asymmetric biomimetic transamination and Mannich reaction, to give various chiral α‐amino acids and α,β‐diamino acid esters in good yields with excellent diastero‐ and/or enantioselectivities. The research has provided some useful information for further applications of the catalytic power of vitamin B6 in the area of asymmetric cayalysis. More details are discussed in the article by Zhao et al. on page 103–112.
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