Reaction Steps
Powdered 4 Å molecular sieves (50 mg) were added to a solution of glycerol 9 (730 mg, 1.02 mmol), phosphite 10 (771 mg, 1.22 mmol) and N-iodosuccinimide (NIS) (275 mg, 1.22 mmol) in dry ether (20 mL) under an atmosphere of nitrogen. The reaction was stirred at room temperature for 15 minutes, trifluoromethanesulfonic acid (110 μL, 1.24 mmol) was added and the stirring was continued for 2 h. The reaction was diluted with more ether (50 mL) and the organic layer was washed with 10% sodium thiosulfate solution (30 mL), water (2×20 mL) and dried over magnesium sulfate. The solvent was removed and the residue was purified over silica [hexane/ether 9:1 as eluent] to give 11 (900 mg, 71%, α to β 4:1) as a colourless syrup; Rf 0.6 (hexane/ether, 2:3); νmaxcm−1/(CHCl3) 1716.7; 1H NMR (500 MHz, CDCl3) δ inter alia 8.00 (d, J 7.7, 2H), 7.55 (t, J 7.7 Hz, 1H), 7.38-7.08 (m, 40H, Ar—H), 5.53-5.41 and 5.38-4.43 (m, together 1H, H-2′), 4.96 (d, 1H, J 2 Hz, H-1), 4.91 (d, 1H, J 2 Hz, H-1), 4.86 (d, 2H, J 11 Hz, PhCH2), 4.82 (d, 2H, J 11 Hz, PhCH2), 4.72 (d, 2H, J 12.5 Hz, PhCH2), 4.69 (d, 2H, J 12.5 Hz, PhCH2), 4.65-4.55 (m, 4H), 4.52-4.42 (m, 4H), 4.13-3.50 (m, 16H); 13C NMR (125 MHz, CDCl3) 8 inter alia 165.9 (CO), 138.6, 138.5, 138.5, 138.43, 138.42, 138.35 (ipso-C), 133.2 (Cq-benzoyl), 130.0, 129.8, 128.5, 128.41, 128.35, 128.33, 128.29, 128.03, 127.92, 127.87, 127.81, 127.78, 127.76, 127.73, 127.63, 127.60, 127.52, 98.4 and 97.7 (2×C-1), 80.0, 79.9, 75.1, 75.0, 74.9, 74.8, 74.7, 73.42, 73.38, 72.68, 72.65, 72.4, 72.3, 72.2, 71.4, 69.2, 69.1, 65.9, 65.5; LRMS-ESI (+ve) m/z (%) 1265 [MNa+1]+ (18), 1264 (MNa+,47), 91 (100); HRMS-ESI (+ve) (Found: m/z 1241.5595 (MH+). C78H81O14 requires m/z 1241.5626).
