2-Cyclohexyl-d6-idene-acetic Acid Ethyl Ester is the labeled analogue of 2-Cyclohexylidene-acetic Acid Ethyl Ester (C987940), a reactant used in the preparation of ethyl 1-(tert-butoxycarbonyl)-4-(1-pyrrolidinyl)-4-piperidineacetate, an intermediate of a novel antiarteriosclerotic agent.