2,2-Dimethyl-3-butenoic Acid Ethyl-d5 Ester is labelled 2,2-Dimethyl-3-butenoic Acid Ethyl Ester (D469060), the ethyl ester of 2,2-Dimethyl-3-butenoic Acid (D469055) which is an constituent in the synthesis of metabolites of Simvastatin (S485000), a synthetic derivative of a fermentation product of Aspergillus terreus.