Anju Chadha

Biocatalytic reduction of alkyl 2-oxopropanoates were carried out by utilizing the whole cells of Candida parapsilosis ATCC 7330 to form the optically enriched alkyl 2-hydroxypropanoates with good enantiomeric excess (ee) (≤91%) and isolated yields (≤68%). Enantiomerically enriched (S)-ethyl 3-bromo-2-hydroxypropanoate thus synthesized by biocatalytic reduction of ethyl 3-bromo-2-oxopropanoate is presented in this study for the first time in water under ambient reaction conditions in a reaction time of 4 h which is considerably less than earlier reported procedures.

This review highlights the importance of the biocatalyst, Candida parapsilosis for oxidation and reduction reactions of organic compounds and establishes its versatility to generate a variety of chiral synthons. Appropriately designed reactions using C. parapsilosis effect efficient catalysis of organic transformations such as deracemization, enantioselective reduction of prochiral ketones, imines, and kinetic resolution of racemic alcohols via selective oxidation. This review includes the details of these biotransformations, catalyzed by whole cells (wild type and recombinant strains), purified enzymes (oxidoreductases) and immobilized whole cells of C. parapsilosis. The review presents a bioorganic perspective as it discusses the chemo, regio and stereoselectivity of the biocatalyst along with the structure of the substrates and optical purity of the products. Fermentation scale biocatalysis using whole cells of C. parapsilosis for several biotransformations to synthesize important chiral synthons/industrial chemicals is included. A comparison of C. parapsilosis with other whole cell biocatalysts for biocatalytic deracemization and asymmetric reduction of carbonyl and imine groups in the synthesis of a variety of enantiopure products is presented which will provide a basis for the choice of a biocatalyst for a desired organic transformation. Thus, a wholesome perspective on the present status of C. parapsilosis mediated organic transformations and design of new reactions which can be considered for large scale operations is provided. Taken together, C. parapsilosis can now be considered a ‘reagent’ for the organic transformations discussed here.