合成路线1

The optical resolution of racemic 2-benzylsuccinic acid (XV) using the chiral amines (R)-1-phenylethylamine (VII), (R)-1-(1-naphthyl)ethylamine (XIV) or (S)-1-phenyl-2-(4-tolyl)ethylamine (XVI) is carried out by fractional crystallization of the corresponding diastereomeric salts and treatment with 2N HCl, providing the desired enantiomer 2(S)-benzylsuccinic acid (XVII). Reaction of (XVII) with SOCl2 gives the corresponding acyl chloride (XVIII), which is treated with 4-nitrophenol (XIX) and TEA in dichloromethane to yield the activated diester (XX). The regioselective reaction of (XX) with cis-perhydroisoindole (V) in dichloromethane affords the monoamide (XXI), which by reaction with HCl and methanol provides the corresponding methyl ester (XXII). This ester is hydrolyzed with NaOH to the previously described chiral succinamic acid (XIII), which is finally converted into its calcium salt.