Chemo‐ and Stereoselective Reduction of β‐Keto‐α‐oximino Nitriles by Using Baker's Yeast

Abstract

AbstractThe baker's yeast mediated reduction of β‐keto‐α‐oximino nitriles 3 at 20 °C gave β‐hydroxy‐α‐oximino nitriles 4 in high yields with high enantiomeric purity [enantiomeric excess (ee) values >99 %]. At room temperature, the same reaction afforded the product in a slightly lower yield. The β‐hydroxy‐α‐oximino nitriles 4 were obtained as single stereoisomers according to chiral GC–MS analyses and the 1H and 19F NMR spectra of the corresponding Mosher esters. The absolute stereochemistry of alcohol 4a was determined by hydrolysis of its oximino nitrile group followed by conversion into its corresponding α‐hydroxy ester. The β‐hydroxy‐α‐oximino nitrile products were further submitted to oxime‐ and nitrile‐selective transformations. This chemo‐ and stereoselective reduction can be used to generate important chiral building blocks.