Reaction Steps
A reaction mixture of (R)-3-benzyloxy-tetradecanoic acid 15 (100 mg, 0.293 mmol) and DCC (93 mg, 0.450 mmol) in DCM (5 mL) was stirred at room temperature for 10 min, and then disaccharide 21 (300 mg, 0.225 mmol) in DCM (3 mL) and DMAP (11 mg, 0.090 mmol) were added. The reaction mixture was stirred at room temperature for 14 h, after which the solids were removed by filtration, and the residue washed with DCM (2×1 mL). The combined filtrates were concentrated in vacuo, and the residue was purified by silica gel column chromatography (hexane/ethyl acetate, 4/1, v/v) to give 22 as a white solid (319 mg, 86%). Rf=0.41 (hexane/ethyl acetate, 2/1, v/v). [α]26D=−2.8° (c=1.0, CHCl3). 1H NMR (500 MHz, CDCl3): δ 7.33-7.15 (m, 19H, aromatic), 5.94-5.85 (m, 2H, NH, OCH2CH═CH2), 5.45 (t, 1H, J2′,3′=J3′,4′=9.5 Hz, H-3′), 5.34 (d, 1H, J=17.5 Hz, OCH2CH═CH2), 5.22 (d, 1H, J=10.0 Hz, OCH2CH═CH2), 5.08-4.95 (m, 7H, H-1, H-3, H-3L, C6H4(CH2O)2P), 4.61-4.44 (m, 10H, H-1, H-4′, 3×CH2Ph, OCH2CH═CH2), 3.96 (d, 1H, J6′a,6′b=10.5 Hz, H-6′a), 3.88-3.85 (m, 1H, H-3S), 3.80 (d, 1H, J6a,6b=9.5 Hz, H-6a), 3.72-3.66 (m, 3H, H-5′, H-6b, H-6′b), 3.55-3.52 (m, 2H, H-4, H-5), 3.47-3.41 (m, 1H, H-2′), 3.27 (dd, 1H, J1,2=7.5 Hz, J2,3=10.0 Hz, H-2), 2.56 (dd, 1H, J2Sa,2Sb=16.0 Hz, J2Sa,3S=7.0 Hz, H-2Sa), 2.43 (dd, 1H, J2Sa,2Sb=16.0 Hz, J2Sb,3S=7.0 Hz, H-2Sb), 2.35 (dd, 1H, J2La,2Lb=15.0 Hz, J2La,3L=6.0 Hz, H-2La), 2.30-2.20 (m, 3H, H-2L′, H-2L′b), 1.59-1.52 (m, 6H, H-4L, H-4S, H-3L′), 1.23 (broad, 52H, 26×CH2, lipid), 0.90 (s, 9H, SiC(CH3)3), 0.88-0.84 (m, 9H, 3×CH3, lipid), 0.12 (s, 6H, Si(CH3)2). 13C NMR (75 MHz, CDCl3): δ 173.40 (C═O), 170.55 (C═O), 169.94 (C═O), 154.42 (C═O), 138.46-127.35 (aromatic, OCH2CH═CH2), 118.74 (OCH2CH═CH2), 99.29 (C-1′), 96.96 (C-1), 75.89, 75.62, 74.75, 74.28, 74.02, 73.67, 73.41, 71.34, 70.89, 68.87-67.85 (m), 66.48, −4.18 (Si(CH3)2), −5.38 (Si(CH3)2). HR MS (m/z) calculated for C91H139N4O19Psi[M+Na]+, 1673.9438. found, 1674.1754.
