Synthesis of the Constrained L-Methionine Analog, (Z)-L-2-Amino-4-methylthio-3-butenoic Acid

The methionine analog, (Z)-L-2-amino-4-methylthio-3-butenoic acid (1) has been synthesized. The key intermediate, (Z)-(±)-methyl 2-acetamido-4-methylthio-3-butenoate (7) was converted to 1 by enantioselective ester hydrolysis using alcalase (Z)-L-2-acet- amido-4-methylthio-3-butenoic acid (8), followed by enzymatic removal of the N-acetyl group using hog kidner acylase