Rhizopus arrhizus mediated SAR studies in chemoselective biotransformation of haloketones at ambient temperature

Abstract

We have demonstrated a green chemistry approach using the fungus Rhizopus arrhizus for the reductive dehalogenation and synthesis of chiral secondary carbinols and halohydrins of pharmaceutical importance in mild, inexpensive, and environmental friendly process at ambient temperature. In the present study, we have succeeded in unravelling the relationship between the position of the substituent group in the structure of substrate and bioreduction activity of the fungus Rhizopus arrhizus. The asymmetric reduction of the carbonyl group to corresponding chiral halohydrin takes place with good yield and excellent enantiomeric excess (≥92%) when the substituent halogen is on the aromatic nucleus. However, novel results concerning reductive dehalogenation are obtained when halogen is incorporated in the alkyl side chain. Thus, the fungus Rhizopus arrhizus has great potential to bring chemoenzymatic biotransformation of halo ketones. Various influential processing parameters such as microbe selection, temperature, pH, etc. were also investigated to optimize the growth of biocatalyst.