(3Z,6Z,9Z,12Z,15Z)-21,21-Dimethoxyhenicosa-3,6,9,12,15-pentaene is a by-product in the synthesis of (all-Z)-6,9,12,15,18-Heneicosapentaenoic Acid Methyl Ester (H245615), which is the methyl ester derivative of (all-Z)-6,9,12,15,18-Heneicosapentaenoic Acid (H245600); a 21-carbon, ω-3 fatty acid which is a dietary precursor to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Also administered in a high dose for pain relief.