Dynamic kinetic resolution of phenylglycine esters via lipase-catalysed ammonolysis

Ammonolysis of D,L-phenylglycine methyl ester catalysed by Novozym 435 at 4 0 degrees C in tert-butyl alcohol gave D-phenylglycine amide in 78% ee at 4 6% conversion, corresponding to an enantiomeric ratio (E) of 16. Lowering t he temperature improved the enantioselectivity (E=52 at -20 degrees C). Com bination of ammonolysis with pyridoxal-catalysed in situ racemisation of th e unconverted ester (dynamic kinetic resolution), at -20 degrees C, gave D- phenylglycine amide with 88% ee at 85% conversion. The amide racemised much slower than the ester at this low temperature. (C) 1999 Elsevier Science L td. All rights reserved.