合成路线1

In a further process, the racemic trans glycidic ester (XII), prepared by Darzen's condensation between anisaldehyde (X) and methyl chloroacetate (XI), was resolved by enantioselective enzymatic hydrolysis, using several different enzymes and reaction conditions to produce the undesired (2S,3R) acid (XIII), while leaving intact the required (2R,3S)-glycidic ester (XIV) (4-7). Opening of the chiral epoxide (XIV) with 2-aminobenzenethiol (VII) proceeded with retention of the configuration, producing methyl (2S,3S)-2-hydroxy-3-(2-aminophenylsulfanyl)-3-(4-methoxyphenyl)propionate (XV) (8). Alternatively, the (S,S)-amino ester (XV) was obtained by resolution with tartaric acid of the racemic three-adduct resulting from epoxide (XII) and 2-aminobenzenethiol (VII) (9). Cyclization of amino ester (XV) in refluxing xylene in the presence of p-toluenesulfonic acid afforded the target lactam (VIII) (9). The cyclization of (XV) to lactam (VIII) was also accomplished by means of trichloroacetic acid or under basic conditions