Laboratory scale-up synthesis of chiral carbinols using Rhizopus arrhizus

Rhizopus arrhizus mediated bioreduction was optimized using acetophenone as a model substrate. Various parameters such as bio-processing conditions, reaction time, substrate concentration, temperature, and solvent carrier were studied. This optimized protocol was further exploited for scaled up bioreductions of various prochiral ketones. This study demonstrates the versatility of the fungus Rhizopus arrhizus as a biocatalyst to obtain chiral carbinols in good to excellent yields and selectivities.

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(S)-1-PhenylethanolC8H9O83.4% ee[α]D23 = −45.9 (c 0.974, CHCl3)Source of chirality: Microbial reductionAbsolute configuration: (S)

(S)-1-(Benzofuran-2-yl) ethanolC10H9O291.7% ee[α]D26 = −16.6 (c 0.728, CHCl3)Source of chirality: Microbial reductionAbsolute configuration: (S)

(S)-6-Fluorochroman-4-olC9H9FO2>99% ee[α]D24 = −48.4 (c 0.320, CHCl3)Source of chirality: Microbial reductionAbsolute configuration: (S)

(S)-4-Phenyl-2-butanolC10H14O94.6% ee[α]D25 = +16.5 (c 0.569, CHCl3)Source of chirality: Microbial reductionAbsolute configuration: (S)

(R)-1-Phenyl-2-butanolC10H14O97.1% ee[α]D24 = −28.7 (c 0.436, CHCl3)Source of chirality: Microbial reductionAbsolute configuration: (R)

(S)-t-Butyl-3-hydroxybutanoateC8H16O3>99% ee[α]D26 = +28.6 (c 0.483, CHCl3)Source of chirality: Microbial reductionAbsolute configuration: (S)

(S)-α-Phenyl-2-pyridylmethanolC12H11NO78.3% ee[α]D25 = +120.9 (c 0.492, CHCl3)Source of chirality: Microbial reductionAbsolute configuration: (S)