Reaction Steps
A suspension of trichloroacetimidate 12 (1.04 g, 1.21 mmol), acceptor 8 (740 mg, 1.82 mmol) and molecular sieves (4 Å, 500 mg) in DCM (20 mL) was stirred at room temperature for 1 h. The mixture was cooled (−60° C.) and then TMSOTf (18 μL, 0.09 mmol) was added. After stirring the reaction mixture for 15 min, it was quenched with solid NaHCO3. The solids were removed by filtration, and the filtrate was washed with saturated aqueous NaHCO3 (2×50 mL) and brine (2×40 mL). The organic phase was dried (MgSO4) and filtered. Next, the filtrate was concentrated in vacuo. The residue was purified by silica gel column chromatography (hexane/ethyl acetate, 2/1, v/v) to give 13 as a colorless solid (1.09 g, 79%). Rf=0.37 (DCM/methanol, 50/1, v/v). [α]26D 3.8 (c=1.0, CHCl3). 1H NMR (600 MHz, CD3COCD3): δ 7.84-7.20 (m, 22H, aromatic), 6.98 (d, 1H, JNH′,2′=9.0 Hz, NH′), 5.83 (m, 1H, OCH2CH═CH2), 5.41 (t, 1H, J2′,3′=J3′,4′=9.6 Hz, H-3′,), 5.29-5.21 (m, 3H, OCH2CH═CH2, C6H4(CH2O)2P), 5.13-5.03 (m, 3H, H-1′, OCH2CH═CH2, C6H4(CH2O)2P), 4.96-4.91 (m, 2H, CH2aPh, C6H4(CH2O)2P), 4.73-4.45 (m, 7H, H-1, H-4′, CH2bPh, CH2Ph, OCH2CH═CH2), 4.24-4.13 (m, 4H, H-6, CO2CH2, Fmoc, CO2CH2CH, Fmoc), 3.93-3.79 (m, 4H, H-5′, H-6a, H-6′a, H-6′b), 3.69 (m, 1H, H-2′), 3.54 (broad, 3H, H-3, H-4, H-5), 3.19 (dd, 1H, J1,2=7.8 Hz, J2,3=9.0 Hz, H-2), 0.92 (s, 9H, SiC(CH3)3), 0.17 (s, 6H, Si(CH3)2). 13C NMR (75 MHz, CD3COCD3): δ 156.39 (C═O), 155.28 (C═O), 144.96-120.56 (aromatic, OCH2CH═CH2), 118.41 (OCH2CH═CH2), 101.14 (C-1′), 97.33 (C-1), 78.54, 77.87, 75.72, 75.25-74.42 (m), 73.83, 70.35, 69.52, 69.04-68.73 (m), 67.91, 67.12, 57.03 (C-2′), 47.64 (CO2CH2, Fmoc), 25.83 (SiC(CH3)3), 18.27 (SiC(CH3)3), −3.85 (Si(CH3)2), −5.21 (Si(CH3)2). HR MS (m/z) calculated for C59H69N4O16PSi[M+Na]+, 1171.4113. found, 1171.4256.
