Reaction Steps
To a mixture of 4a (348.4 mg, 0.4704 mmol) and glacial acetic acid (120 μL) was added 1.0 M TBAF in 2 mL THF over a period of 15 min at 5-10° C. (ice-water bath) with constant stirring. The reaction mixture was stirred at RT for 48 hours. It was then poured into water (100 mL), extracted with diethyl ether (100 mL, 2×), washed successively with saturated aqueous NaHCO3 (100 mL) and water (100 mL), and dried over anhydrous Na2SO4. After removal of solvent, the crude product was chromatographed on silica gel using dichloromethane-methanol to obtain 5a (140.8 mg, 48% yield). TLC: RF=0.65 (CH2Cl2:MeOH, 95:5 v/v); NMR (in CDCl3): δ in ppm 0.85 (3H, t, J=7.5 Hz), 0.95 (3H, t, J=7.0 Hz) 1.23 (26H, m), 1.54 (2H, m), 2.05 (2H, m), 2.38 (4H, m), 2.80 (10H, m), 3.44-3.50 (5H, m), 3.62-3.68 (2H, m), 3.85 (1H, br s, D2O exchangeable), 5.29-5.35 (12H, m); 13C NMR (in CDCl3): δ in ppm 14.3, 18.3, 22.7, 22.9, 25.7, 25.8 (2), 26.3, 29.6, 29.7 (2), 29.8 (2), 29.9 (2), 32.1, 64.4, 70.7, 72.1, 72.7, 127.2, 127.8, 128.1, 128.2, 128.3 (2), 128.4, 128.5, 128.8, 129.7 (2), 132.2, 177.9; FT-IR (cm−1) 3370 (br), 3013, 2954, 2918, 2850, 1712, 1470, 1397, 1382, 1326, 1239, 1123, 1060, 719; HRAPCI-MS m/z: measured 627.5349 ([M+H]+, calcd. 627.5352 for C41H71O4).
