(3Z,6Z,9Z,12Z,15Z)-21,21-diethoxyhenicosa-3,6,9,12,15-pentaeneis a by-product in the synthesis of (all-Z)-6,9,12,15,18-Heneicosapentaenoic Acid Ethyl Ester which is a fatty acid ester from marine oils; it is used for prophylaxis and treatment of hypertension, hypertriglyceridemia, hypercholesterolemia.