Asymmetric Reductions of Ketones, Imines, and Oximes Using Biocatalytic Enzymes Found in Pea Plants
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Date
2011-06
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The Ohio State University
Abstract
In chemistry today, there is an ever growing and inevitable need to mass produce optically active starting materials for areas such as pharmaceutical and natural product synthesis. It is also important to modern chemists that these reactions are carried out under “green” conditions, which implies a significant reduction in the environmental impact of hazardous chemical production, storage, transportation, and waste disposal. This project employs the use of biocatalytic enzymes to generate chiral alcohols and amines via the asymmetric reduction of ketones, imines, and oximes. Initial reductions with prochiral ketones have yielded enantiomeric excess of >98%, with selectivity for either the (R) or (S) enantiomer depending on pea type. In order to further examine the enzymatic reduction capabilities of various types of pea plants, a library of imines and oximes has been synthesized. The library consists of prochiral imines, and oximes with an assortment of substituents, including molecules with electron donating and electron withdrawing groups. Initial reductions of the aryl imines reveal that hydrolysis is a major competing reaction. Biocatalytic reductions of the oximes have thus far been very successful and produced >99% e.e. with selectivity depending on pea type. This is the first reported instance of biocatalytic oxime reductions.
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biocatalytic reductions, green chemistry