Preparation of (S)-β-nitro alcohols by a (R)-selective HNL via enantioselective C-C bond cleavage.

Hydroxynitrile lyase (HNL) catalysed stereoselective synthesis of β-nitro alcohols is considered as an efficient biocatalytic approach. However, there exist only one (S)-selective HNL i.e. Hevea brasiliensis (HbHNL) to synthesize (S)-β-nitro alcohols from corresponding aldehydes. Further, HbHNL synthesis is limited by long reaction time (48 h) and moderate yield. We prepared a number of (S)-β-nitro alcohols using a (R)-selective HNL from Arabidopsis thaliana (AtHNL). Optimization of the reaction conditions of AtHNL catalyzed stereoselective C-C bond cleavage of racemic 2-ntro-1-phenylethanol (NPE) produced (S)-NPE up to 99% ee and 47% conversion. We believe this is the fastest biocatalytic route known so far to synthesize a series of (S)-β-nitro alcohols. This approach widens the application of AtHNL not only to synthesize (R)- but also (S)-β-nitro alcohols starting with appropriate substrate. Without discovering a new enzyme, rather using a different approach, it synthesized a number of (S)-β-nitro alcohols by taking the advantage of the substrate selectivity of AtHNL.