To a solution of (6Z,9Z,29Z,32Z)-19-((9Z,12Z)-octadeca-9,12-dienyl)octatriaconta-6,9,29,32-tetraene-19,20-diol (0.75 g, 0.98 mmol), 5-(dimethylamino)pentanoic acid (285 mg, 2.0 mmol), EDC hydrochloride (378 mg, 2.0 mmol), and 4-(N,N-dimethylamino)pyridine (5 mg) in anhydrous dichloromethane (10 mL) was added DIPEA (0.68 mL, 3.9 mmol). The reaction was stirred for 16 hours at room temperature under nitrogen. TLC (1:1 hexanes/ethyl acetate) indicated that the reaction had stalled, so additional 5-(dimethylamino)pentanoic acid (70 mg, 0.5 mmol) and fresh EDC hydrochloride (300 mg, 1.6 mmol) were added. The reaction was stirred for an additional 24 hours under nitrogen at room temperature. The solution was diluted with dichloromethane (100 mL) and washed with saturated sodium bicarbonate (50 mL), water (50 mL), and brine (50 mL). The combined aqueous layers were back extracted once with dichloromethane (50 mL). The combined dichloromethane extracts were dried on magnesium sulfate, filtered, and concentrated in vacuo to dryness. The resulting orange oil was purified by column chromatography on silica gel 60 (eluted with a gradient of 25%→50% ethyl acetate in hexanes) to afford (6Z,9Z,29Z,32Z)-20-hydroxy-20-((9Z,12Z)-octadeca-9,12-dienyl)octatriaconta-6,9,29,32-tetraen-19-yl 5-(dimethylamino)pentanoate as a pale yellow oil (560 mg, 64%). 1H NMR (400 MHz, CDCl3) δ 5.43-5.29 (m, 12H), 4.95 (dd, 1H, J=10.1, 2.7 Hz), 2.78 (t, 6H, J=6.5 Hz), 2.38 (t, 2H, J=7.5 Hz), 2.28 (t, 2H, J=7.5 Hz), 2.22 (s, 6H), 2.09-2.02 (m, 12H), 1.72-1.42 (m, 13H), 1.41-1.19 (m, 56H), 0.90 (t, 9H, J=6.7 Hz).
