合成路线1

3-Indolylcarboxylic acid (I) was converted to acid chloride (II) with oxalyl chloride in refluxing CH2Cl2, and subsequently condensed with cis 1,2-cyclohexanediamine (III) to provide racemic amide (IV). Coupling of (4-methylphenyl)acetyl chloride (VI) with D-3-(2-naphthyl)alanine (V) was carried out via previous silylation of the amino acid with bis(trimethylsilyl)acetamide in THF. The resulting amide (VII) was N-alkylated with ICH3 in the presence of NaH to provide (VIII). Then, the chiral acyl amino acid (VIII) was coupled to racemic amine (IV) using 1-ethyl-3-(3-dimethylaminopropyl)- carbodiimide-HCl (EDC) and 7-aza-1-hydroxybenzotriazole (HOAt) to furnish the corresponding amide as a diastereomeric mixture, from which the desired isomer was isolated by reverse phase chromatography.