Dynamic kinetic resolution of phenylglycine esters via lipase-catalysed ammonolysis
摘要:
Ammonolysis of D,L-phenylglycine methyl ester catalysed by Novozym 435 at 40 degrees C in tert-butyl alcohol gave D-phenylglycine amide in 78% ee at 46% conversion, corresponding to an enantiomeric ratio (E) of 16. Lowering the temperature improved the enantioselectivity (E=52 at -20 degrees C). Combination of ammonolysis with pyridoxal-catalysed in situ racemisation of the 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 Ltd. All rights reserved.