Chemoenzymatic one-pot synthesis of enantiopure L-arylalanines from arylaldehydes

Various enantiopure L-arylalanines can be prepared from the corresponding arylaldehydes in one-pot fashion by a combination of chemical and enzymatic reactions. The reagents used were (triphenyl-lambda(5)-phosphanylidene) ethyl acetate (Wittig reaction), porcine liver esterase (PLE), phenylalanine ammonia lyase (PAL) from parsley and ammonia. As examples the following aryl groups were used: phenyl, 4-chlorophenyl, 3-fluorophenyl and thiophen-2-yl. The pure L-enantiomers of phenyl-, 4-chlorophenyl-, 3-fluorophenyl- and thiophen-2-ylalanines were obtained after ion-exchange chromatography in 88, 78, 72 and 91% yields, respectively, calculated from the arylaldehydes. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).