Reaction Steps
DDQ (49.0 mg, 0.21 mmol) was added to a solution of compound 5 (0.22 g, 0.18 mmol) in a mixture of dichloromethane and water (2.2 mL, 10/1, v/v). The reaction mixture was stirred vigorously at room temperature for 2 h in the dark and then quenched with an aqueous mixture of citric acid, ascorbic acid, and NaOH (0.1 mL, 1.2%, 1.0%, 0.92% w/v). The mixture was diluted with ethyl acetate (15 mL) and washed with aqueous NaHCO3 (sat., 5 mL). The organic layer was dried (MgSO4) and filtered, and the filtrate concentrated in vacuo. The residue was purified by silica gel column chromatography (hexane/ethyl acetate, 4/1, v/v) to give 6 (0.18 g, 94%) as a clear oil. Rf=0.30 (hexane/ethyl acetate, 4/1, v/v). [α]25D=+66.0 (c 0.87, CHCl3); 1H (500 MHz, CDCl3): δ 7.41-7.30 (m, 30H, aromatic), 5.38 (dd, 1H, J1′2′=8.0 Hz, J2′,3′=8.5 Hz, H-2′), 5.20 (bd, 2H, CH2-LCbz), 4.93 (d, 1H, CHH—OBn), 4.83-4.81 (bd, 1H, H-1), 4.70-4.66 (dd, 2H, CH2, OBn), 4.58-4.42 (m, 8H, 5×CHH, OBn, CH2-LBn), 4.34 (d, 1H, J1′,2′=8.0 Hz, H-1′), 4.11 (t, 1H, J2,3=9.5 Hz, J3,4=9.0 Hz, H-3), 3.89-3.88 (bd, 1H, H-4′), 3.73-3.60 (m, 7H, H-4, H-6a,b, H-5′, H-6′a,b, H-5), 3.47-3.43 (m, 2H, H-3′, CHH-L), 3.29-3.22 (m, 3H, 3×CHH-L), 3.16-3.13 (dd, 1H, J2,3=9.5 Hz, J1,2=3.5 Hz, H-2), 1.96 (s, 3H, COCH3), 1.61-1.54 (m, 4H, CH2-L), 1.36-1.27 (m, 2H, CH2-L). 13C (75 MHz, CDCl3): δ169.45, 138.39, 138.18, 137.88, 137.55, 128.76, 128.73, 128.64, 128.54, 128.45, 128.22, 128.18, 128.07, 128.04, 127.94, 127.91, 127.72, 127.49, 101.80 (C-1′), 98.10 (C-1), 81.47, 80.47, 76.83, 74.71, 74.21, 74.00, 73.79, 72.40, 72.29, 71.40, 69.80, 69.56, 68.68, 68.40, 68.30, 67.36, 62.59, 29.26, 23.49, 21.21. HR-MALDI-TOF/MS (m/z) calcd for C62H70N4O13[M+Na]+: 1101.4829. found: 1101.4831.
