Reaction Steps
To a solution of vanillin (330 mg, 2.2 mmol), cis-eicosapentaenoic acid (800 mg, 2.65 mmol) and catalytic amount of 4-(dimethylamino)pyridine in dichloromethane (DCM, 15 mL) was added a solution of N,N′-dicyclohexylcarbodiimide (720 mg, 3.53 mmol) in DCM (5 mL) for 5 min at ice cold temperature. The mixture was stirred at rt for 16 h and diluted with water. DCM layer was separated and the aqueous layer was extracted with DCM (3×100 mL). The combined DCM layer was washed with water, brine and dried over sodium sulfate. The solution was filtered and the residue was chromatographed over silica gel column using hexane-ethyl acetate (95:5) as an eluent to give the product as an oil (710 mg, 75%). IR (neat) νmax 3012, 2961, 2931, 2855, 1767, 1701, 1600, 1271, 1149, 1119, 1032 cm−1; 1H NMR (400 MHz, CDCl3) δ 9.94 (1H, s, —CHO), 7.49 (1H, d, J=1.6 Hz, H-2), 7.47 (1H, dd, J=8.0, 1.6 Hz, H-6), 7.20 (1H, d, J=8.0 Hz, H-5), 5.30-5.48 (10H, m, H-5′, 6′, 8′, 9′, 11′, 12′, 14′, 15′, 17′, 18′), 3.89 (3H, s, —OCH3), 2.80-2.88 (8H, m, H-7′, 10′, 13′, 16′), 2.58-2.67 (2H, m, H-2′), 2.22-2.25 (2H, m, H-19′), 2.05-2.11 (2H, m, H-4′), 1.81-189 (2H, m, H-3′), 0.97 (3H, t, J=7.4 Hz, H-20′).
