A NEW CHEMOENZYMATIC ROUTE FOR THE STEREOCONTROLLED SYNTHESIS OF OPTICALLY PURE 3-(2-PYRIDYL)ALANINE

A new chemoenzymatic synthesis of optically pure 3-(2-pyridyl)alanine (IV)was established ,which comprised the stereocontrolled amination of olefinic bond in compound 3-(2pyridyl)acrylic acid(III)catalyzed by L-phenylalanine ammonialyase(PAL, EC 4.3.1.5)con-tained in Rhodotorula rubra mycelium. Compound III was prepared chemically from 1,1,1-trichloro-2hydroxy-3-(2-pyrdyl)propane(II) which was formed by addition of chloral to α-picoline(I).Theenzymatic amination of compound IIl was completed in aqueous ammonia solution(6.4 mol/L,pH10.5, 30℃)with the conversion of 60%,The preduct IV was separated ftom the unconverted III bysilica gel dry column chromatography and further purified by non-polar resin(CGA-688 )columnchromatography.The specific rotation α_D²⁴=36.25°(c 0.250, H₂O).