The hydrogenation of 4-isopropylbenzoic acid (I) with H2 over PtO2 in acetic acid gives 4-isopropylcyclohexanecarboxylic acid as a mixture of cis- and trans-isomers (II). This mixture is esterified with methanol to the corresponding mixture of methyl esters (III), which is isomerized with NaH at 150 C without solvent, affording the trans-methyl ester (IV). Hydrolysis of (IV) with NaOH in methanol - water gives the free acid (V), which is finally condensed with D-phenylalanine (VI) by means of N-hydroxysuccinimide and dicyclohexylcarbodiimide in chloroform.