Simultaneous synthesis of enantiomerically pure (S)-amino acids and (R)-amines using alpha/omega-aminotransferase coupling reactions with two-liquid phase reaction system

Abstract

An efficient simultaneous synthesis of enantiopure (S)-amino acids and chiral (R)-amines was achieved using alpha/omega-aminotransferase (alpha/omega-AT) coupling reaction with two-liquid phase system. As, among the enzyme components in the alpha/omega-AT coupling reaction systems, only omega-AT is severely hampered by product inhibition by ketone product, the coupled reaction cannot be carried out above 60 mM substrates. To overcome this problem, a two-liquid phase reaction was chosen, where dioctylphthalate was selected as the solvent based upon biocompatibility, partition coefficient and effect on enzyme activity. Using 100 mM of substrates, the AroAT/omega-AT and the AlaAT/omega-AT coupling reactions asymmetrically synthesized (S)-phenylaianine and (S)-2-aminobutyrate with 93% (>99% ee(S)) and 95% (>99% ee(S)) of conversion yield, and resolved the racemic alpha-methylbenzylamine with 56% (95% ee(R)) and 54% (96% ee(R)) of conversion yield, respectively. Moreover, using 300 mM of 2-oxobutyrate and 300 mM of racemic alpha-methylbenzylamine as substrates, the coupling reactions yielded 276 mM of (S)-2-aminobutyrate (>99% ee) and 144 mM of (R)-alpha-methylbenzylamine (>96% ee) in 9 h. Here, most of the reactions take place in the aqueous phase, and acetophenone mainly moved to the organic phase according to its partition coefficient. (C) 2003 Published by Elsevier B.V.