Reaction Steps
To a solution of compound 8 (1.21 g, 3.71 mmol) in anhydrous DMF (15 mL), under nitrogen and cooled at 0° C., was added NaH (116 mg, 4.83 mmol). The reaction mixture was stirred 15 minutes at 0° C. and treated with benzyl bromide (0.66 mL, 5.57 mmol). After 12 hours at room temperature, the reaction mixture was cooled at 0° C., quenched by slow addition of water and extracted with chloroform. The combined organic layers were washed with H2O, dried over anhydrous Na2SO4, filtered and the solvents were evaporated. Purification by chromatography on silica gel (ethyl acetate-petroleum ether, v/v 1:3) afforded 91% as white crystals in 91% yield (2.01 g). mp=59-61° C.; [αD]24=−23° (c 1, CHCl3); 1H NMR (500 MHz, CDCl3): δ3.48 (dd, 1H, J2,3 9.6 Hz, J3,4 2.8 Hz, H-3), 3.63 (bs, 3H, H-5, H-6a and H-6b), 3.75 (s, 3H, OMe), 3.90 (d, 1H, J4,5<1.5 Hz, H-4), 4.01 (dd, 1H, J1,2 7.8 Hz, H-2), 4.22 (m, 2H, OCH2), 4.40, 4.45, 4.64, 4.84, 4.96 and 4.97 (6 d, 1H each, JA,B 11.7 Hz, CH2Ph), 4.83 (d, 1H, H-1), 5.19 and 5.33 (2 dd, 1H each, CH═CH2), 5.95 (m, 1H, CH═CH2), 6.78 and 7.02 (2 d, 2H each, C6H4), 7.22-7.40 (m, 15H, 3C6H5). Anal. Calcd for C37H40O7 (596.7): C 74.48, H 6.76; found: C 74.32, H 6.75.
