Strecker condensation of 3-hydroxybenzaldehyde (I) with trimethylsilyl cyanide in the presence of (S)-2-phenylglycine (II) yielded the chiral aminonitrile (III) as the major diastereoisomer. Oxidative cleavage of the chiral auxiliary of (III) with lead tetraacetate, followed by acid hydrolysis of the nitrile group provided the (S)-amino acid (IV), which was esterified with MeOH and Me3SiCl. The resulting aminoester (V) was coupled with carboxylic acid (VI) using diphenylphosphoryl azide to form amide ester (VII). Finally, saponification of the methyl ester of (VIII) afforded the target carboxylic acid.

Strecker condensation of 3-cyanobenzaldehyde (I) with trimethylsilyl cyanide in the presence of (S)-2-phenylglycine (II) yielded the chiral aminonitrile (III) as the major diastereoisomer. Oxidative cleavage of the chiral auxiliary of (III) with lead tetraacetate, followed by acid hydrolysis of the nitrile groups provided the (S)-amino acid (IV), which was esterified with MeOH and Me3SiCl. The resulting aminoester (V) was coupled with carboxylic acid (VI) using diphenylphosphoryl azide to form amide ester (VII). Finally, saponification of both methyl esters of (VII) afforded the target dicarboxylate salt.