Reaction Steps
To a solution of the starting material (7) (1.0 g, 2.66 mmol) and imidazole (200 mg, 2.93 mmol) in DMF (3.0 ml) at 0° C., was slowly added TBDMSCl (442 mg, 2.93 mmol) in four portions over 1 h. After 2 h, the volatiles were evaporated under reduced pressure and the residue was adsorbed on silica gel and purified by flash chromatography (EtOAc, EtOAc:MeOH 9.5:0.5). The expected product (8) was isolated as a crystalline solid (826 mg, 64%). 1H NMR (d6 DMSO) δ 0.00 (s, 1H, CH3); 0.01 (s, 1H, CH3), 0.79 (s, 9H, tBu), 1.87-1.80 (m, 1H, H-2′), 2.12 (ddd, J=13.0, 5.8 and 3.0 Hz, 1H, H-2′), 3.65 (dd, J=11.5, 2.9 Hz, 1H, H-5′), 3.74 (dd, J=11.5, 2.5 Hz, 1H, H-5′), 3.81-3.80 (m, 1H, H-4′), 4.10-4.09 (m, 1H, H-3′), 4.17 (d, 2H, J=5.1 Hz, NCH2), 5.19 (d, 1H, J=4.0 Hz, 3′-OH), 6.04 (t, J=6.6 Hz, 1H, H-1′), 6.83 (br s, 1H, NHH), 7.78 (br s, 1H, NHH), 7.90 (s, 1H, H-6), 9.86 (t, J=5.1 Hz, 1H, —H2CNH); MS (ES): m/z (%) (MH)+ 491 (40%).
