反応手順
Compound 6a (50 mg, 0.11 mmol) was dissolved in 2 mL of 2N H2SO4 and stirred for 2 days at room temperature. The reaction mixture was neutralized with NaHCO3 and lyophilized. The compound was extracted with EtOH (2×10 mL) and concentrated to dryness. The residue was purified by column chromatography (silica gel 230-400 mesh, elution with 7:1:0.3 chloroform:methanol:NH4OH). The desired fractions were combined, concentrated, and dried in vacuo. The product was dissolved in 3 mL of EtOH and 2N H2SO4 was added dropwise. The resulting sulfate salt that precipitated out was filtered, and washed with EtOH. This product, which was hygroscopic in nature, was dissolved in water (2 mL) and lyophilized to give a white solid: yield 20 mg (29%), MS: m/z 354 (M+H)+; 1HNMR (DMSO-d6) δ 8.25 (s, 1H, H-2), 7.80 (bs, 2H, O—NH2), 5.87 (d, 1H, H-1′, J1′,2′=5.7 Hz), 4.88 (t, 1H, H-2′, J2′,3′=5.2 Hz), 4.35-4.40 (bm, 1H, H-4′), 4.23 (t, 1H, H-3′, J2′,3′=3.2 Hz), 4.10 (t, 2H, NH2O—CH2), 3.50-3.57 (m, 1H, 5′-CH2), 3.65-3.72 (m, 1H, 5′-CH2), 3.45 (bm, 2H, N(CH3)—CH2), 2.85 (s, 3H, N—CH3), 2.58 (s, 3H, 8-CH3); UV λmax, nm, pH 1, 274 (∈ 15,200), pH 7, 276 (∈ 15,500), pH 13, 277 (∈ 15,900). Anal. (C14H23N7O4.2.2H2SO4.0.1C2H5OH.0.5H2O) C, H, N.
