Asymmetric synthesis of lipitor chiral intermediate using a robust carbonyl reductase at high substrate to catalyst ratio

An NADPH-dependent carbonyl reductase (RpCR) from Rhodococcus pyridinivorans was discovered by genome mining for the asymmetric reduction of ethyl 4-chloro-3-oxo-butanoate (COBE). RpCR has been soluble expressed in Escherichia coli BL21(DE3). The highest activity is determined at pH 5.0 and 50 degrees C toward COBE. The apparent K-m and k(cat)/K-m are 0.39 mM and 1747 s(-1) mM(-1), endowing RpCR with high catalytic efficiency in reduction of COBE. Employing merely 0.1 g recombinant RpCR-GDH in a toluene aqueous biphasic system, as much as 7.0 g COBE could be asymmetrically reduced into ethyl (S)-4-chloro-3-hydroxybutanoate [(S)-CHBE] (>99% ee)without addition of external cofactor, achieving molar isolation yield of 91%, substrate to biocatalyst ratio of 70 and space-time yield of 1480 g L-1 d(-1). Our results indicate the robust RpCR could be potentially applied in the preparation of optically pure (S)-CHBE. (C) 2015 Elsevier B.V. All rights reserved.