Improved synthesis of trans-4-alkylcyclohexane carboxylic acids

Several stereomerically pure amino acid derivatives containing the N-terminal trans-4-alkylcyclohexanoyl fragment were obtained. Hydrogenation of 4-alkylbenzoic acids in the presence of a special Ru–Ni/C catalytic system and isomerization of the resulting mixture of trans- and cis-isomers of 4-alkylcyclohexanecarboxylic acids were used as the key steps. The stereomeric configuration of all compounds was confirmed by 1H NMR spectroscopy. The compounds obtained possess a broad biological activity potential and are useful intermediates in the synthesis of stereomerically pure modified peptides.