CHEMOENZYMATIC SYNTHESIS OF POLY[(2R,3S)- BENZYL BETA-3-METHYLMALATE]- BETA-METHYLASPARTASE AS A VERSATILE ENZYME IN THE PREPARATION OF THE CHIRAL PRECURSOR

beta-methylaspartase from Clostridium tetanomorphum was used under unu sual conditions to produce a mixture of natural (2S,3S) and of uncommo n (2S,3R)-3-methylaspartic acid in a 60:40 mol/mol ratio. Both diaster eoisomers were separated during the mutiple-steps synthesis of the lac tone. The new optically active (3R,4R)-3-methylmalolaclonate of benzyl was obtained with a very high diastereoisomeric excess (> 98%), as de termined by chiral gas chromatography, and polymerized by anionic ring -opening polymerization. Poly[(2R,3S)-benzyl beta-3-methylmalate] was semicrystalline (T-m = 130 degrees C) and highly isotactic according t o the C-13 NMR spectrum. Comparison was made with the poly[2S,3S]-ster eoisomer.