Reaction Steps
Compound 8 (5.0 g, 9.6 mmol) was treated with 27% methanolic ammonia solution overnight. After evaporation of the solvent the crude was coevaporated thrice with dry pyridine and dissolved in the same. To this pre-cooled solution was added DMAP (1.17 g, 9.6 mmol) and then dropwise was added phenyl chlorothionoformate (1.6 mL, 11.53 mmol) and reaction stirred overnight. Reaction was quenched with saturated solution of NaHCO3 and extracted with dichloromethane. The organic layer was dried over MgSO4, concentrated and chromatographed over silica gel (10-30% ethyl acetate in cyclohexane, v/v) to give 10 as yellowish foam (4.1 g, 6.72 mmol, 70%). Rf=0.60 (30% ethyl acetate in cyclohexane, v/v). 1H NMR (600 MHz) δ: 8.58 (1H, s, N—H), 7.48 (1H, s, H6), 7.19 (15H, m), 6.44 (1H, d, JH1′,H2′=6.1 Hz, H1′), 5.97 (1H, app t, J=5.8 Hz, H2′), 5.83 (1H, m, H7′), 5.09 (2H, m, H8′-H8″), 4.77 (1H, d, Jgem=11.2 Hz, CH2Bn), 4.55 (3H, m, CH2Bn, H3′), 3.71 (1H, d, JH5′,H5″=10.3 Hz, H5″), 3.48 (1H, d, JH5′,H5″10.3 Hz, H5′), 2.66 (1H, dd, JH6,H6=14.6 Hz, JH6,H7=8.1 Hz, H6″), 2.35 (1H, dd, JH6,H6=14.6 Hz, JH6,H7=8.1 Hz, H6′), 1.51 (3H, CH3, thymine); 13C NMR (125.7 MHz) δ: 194.4 (>C═S), 163.4 (C4), 150.3 (C2), 137.1, 137.2 (aromatic), 135.6 (C6), 132.4 (C7′), 121.6, 126.7, 127.3, 127.6, 127.8, 128.0, 128.1, 128.4, 128.6, 129.3, 129.5 (aromatic), 118.8 (C8′), 111.5 (C5′), 87.1 (C4′), 85.1 (C2′), 82.9 (C1′), 77.8 (C3′), 74.9 (C—CH2Bn), 73.7 (C5′), 73.7 (C—CH2Bn), 37.3 (C6′), 11.9 (CH3, thymine); MALDI-TOF m/z [M+H]+ found 615.16 calcd 615.21.
