Reaction Steps
A solution of (R)-3-benzyloxy-dodecanoic acid 14 (86 mg, 0.281 mmol) and DCC (78 mg, 0.376 mmol) in DCM (5 mL) was stirred at room temperature for 10 min, and then disaccharide 21 (250 mg, 0.188 mmol) in DCM (2 mL) and DMAP (11 mg, 0.094 mmol) were added. The reaction mixture was stirred for another 14 h, after which the solids were removed by filtration, and the residue was 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 36 as a white solid (277 mg, 91%). Rf=0.41 (hexane/ethyl acetate, 2/1, v/v). [α]26D=−3.0° (c=1.0, CHCl3). 1H NMR (600 MHz, CDCl3): δ 7.34-7.15 (m, 19H, aromatic), 6.01 (d, 1H, JNH′,2=7.2 Hz, NH′), 5.92-6.86 (m, 1H, OCH2CH═CH2), 5.46 (t, 1H, J2′,3′=J3′,4′=9.6 Hz, H-3′), 5.34 (d, 1H, J=16.8 Hz, OCH2CH═CH2), 5.22 (d, 1H, J=10.8 Hz, OCH2CH═CH2), 5.08-4.97 (m, 7H, H-1′, H-3, H-3L, C6H4(CH2O)2P), 4.61-4.45 (m, 10H, H-1, H-4′, 3×CH2Ph, OCH2CH═CH2), 3.97 (d, 1H, J6′a,6′b=10.5 Hz, H-6′a), 3.88-3.86 (m, 1H, H-3S), 3.81 (d, 1H, J6a,6b=9.5 Hz, H-6a), 3.73-3.68 (m, 3H, H-5′, H-6b, H-6′b), 3.56-3.46 (m, 3H, H-2′, H-4, H-5), 3.28 (dd, 1H, J1,2=7.8 Hz, J2,3=10.2 Hz, H-2), 2.56 (dd, 1H, J2Sa,2Sb=15.6 Hz, J2Sa,3S=7.2 Hz, H-2Sa), 2.44 (dd, 1H, J2Sa,2Sb=15.6 Hz, J2Sb,S3=6.0 Hz, H-2Sb), 2.36 (dd, 1H, J2La,2Lb=15.0 Hz, J2La,3 L=6.0 Hz, H-2La), 2.30-2.21 (m, 3H, H-2L′, H-2L′b), 1.57-1.53 (m, 6H, H-4L, H-4S, H-3L′), 1.24 (broad, 48H, 24×CH2, lipid), 0.90 (s, 9H, SiC(CH3)3), 0.89-0.85 (m, 9H, 3×CH3, lipid), 0.13 (s, 6H, Si(CH3)2). 13C NMR (75 MHz, CDCl3): δ 173.54 (C═O), 170.64 (C═O), 170.03 (C═O), 154.49 (C═O), 138.52-127.43 (aromatic, OCH2CH═CH2), 118.84 (OCH2CH═CH2), 99.34 (C-1′), 97.02 (C-1), 76.00, 75.70, 74.33, 74.08, 73.73, 73.48, 71.46, 71.01, 68.95-67.99 (m), 66.55, −4.13 (Si(CH3)2), −5.32 (Si(CH3)2). HR MS (m/z) calculated for C89H135N4O19PSi [M+Na], 1645.9125. found, 1646.2435.
