2-Octadecyleicosanoic Acid Ethyl-d5 Ester is labelled 2-Octadecyleicosanoic Acid Ethyl Ester (O235965) which is the ethyl ester of 2-Octadecyleicosanoic acid (O235960) which is used as a reagent to synthesize Lipid Oligonucleitide Conjugates, compounds that act as a “drug delivery” system to mutated/infected cells.