Asymmetric Transamination with Polyethyleneimines

Significance

A homochiral polyethylenimine 1 having S-benzyl side chains promoted asymmetric transamination of α-keto acid 3 with pyridoxamine coenzyme 2 bearing a hydrophobic N-alkyl chain in water to afford enantiomerically enriched valine (S > R) at lower chemical conversion, whereas significant racemization was observed at higher conversion. When the coenzyme was covalently anchored onto the chiral polyethylenimine (e.g., polymers 4 and 5), the racemization was suppressed although the enantioselectivities were lower than those obtained with 1 at low conversion.