6-Methylheptanoic Acid Ethyl-d5 Ester is labelled 6-Methylheptanoic Acid Ethyl Ester (M311875), the ethyl ester of 6-Methylheptanoic acid (M311870) which is used as a reagent to synthesize analogues of Eponemycin, an antibiotic that also exhibits anti-angiogenic activity by inhibiting proteasome function. 6-Methylheptanoic acid naturally occurs as a component of the scent chemical of the brushtail possum.