Reaction Steps
A mixture of 6 (0.098 g, 0.14 mmol) and 7 (0.1 g, 0.092 mmol) was co-evaporated with dry toluene (3×7 mL) and dried in vacuo for 4 h. The dried compounds were dissolved in a mixture of diethyl ether and dichloromethane (7 mL, 5/1, v/v) and 4 Å MS (0.28 g) was added. The mixture was stirred under an atmosphere of argon for 30 min and then cooled (−50° C.). TMSOTf (2.5 μL, 0.014 mmol) was added and the reaction mixture was allowed to reach 0° C. gradually over a period of 1 h. The reaction was then quenched by the addition of pyridine (20 μL), diluted with dichloromethane (7 mL), and filtered through celite. The filtrate was washed with aqueous NaHCO3 (sat., 7 mL) and the organic layer was dried (MgSO4) and filtered, and the filtrate was concentrated in vacuo. The residue was purified by silica gel column chromatography (hexane/ethyl acetate, 4/1, v/v) to give 8 (0.13 g, 86%) as a clear oil. Rf=0.35 (hexane/ethyl acetate, 4/1, v/v). [α]25D=+59.4 (c 1.72, CHCl3); 1H (500 MHz, CDCl3): δ 7.35-7.14 (m, 50H, aromatic), 5.76 (d, 1H, J1″,2″=3.0 Hz, H-1″), 5.28 (t, 1H, J2′,3′=9.5 Hz, J1′,2′=8.0 Hz, H-2′), 5.18-5.16 (bd, 2H, CH2-LCbz), 4.89-4.84 (m, 2H, CHH, OBn, H-1), 4.80-4.71 (dd, 3H, 3×CHH, OBn), 4.68-4.62 (m, 5H, 3×CHH, OBn, H-1′), 4.54-4.39 (m, 8H, 3×CH2, OBn, CH2-LBn), 4.35-4.24 (m, 3H, CHH, OBn, H-3, H-5″), 4.18-4.04 (m, 5H, CH2, OBn, H-4, H-3″, H-2″), 3.99 (bs, 1H, H-4″), 3.84 (bs, 1H, H-4′), 3.80-3.74 (m, 2H, H-6a, H-5), 3.65-3.51 (m, 4H, H-6b, H-6′a, H-6″a, b), 3.44-3.30 (m, 5H, CH2-L, H-2, H-5′, H-6′), 3.23-3.17 (m, 3H, CH2-L, H-3′), 1.90 (s, 3H, COCH3), 1.51-1.46 (m, 4H, 2×CH2-L), 1.26-1.20 (m, 2H, CH2-L). 13C (75 MHz, CDCl3): δ 169.26, 139.36, 139.18, 138.70, 138.28, 138.24, 138.15, 138.12, 137.08, 128.77, 128.68, 128.63, 128.59, 128.48, 128.42, 128.37, 128.36, 128.34, 128.29, 128.05, 127.95, 127.93, 127.82, 127.80, 127.70, 127.60, 127.53, 127.41, 127.35, 127.30, 99.64 (C-1′), 97.63 (C-1), 96.22 (C-1″), 81.04, 78.64, 76.84, 76.51, 76.28, 75.54, 74.92, 74.68, 73.68, 73.58, 73.45, 73.23, 72.51, 72.40, 72.19, 71.96, 70.49, 70.16, 69.17, 68.76, 68.33, 68.22, 67.37, 62.64, 53.66, 29.13, 23.41, 21.26. HR-MALDI-TOF/MS (m/z) calcd for C96H104N4O18[M+Na]+: 1623.7246; found: 1623.7242.
