Reaction Steps
6-Amino-2-benzyloxy-3-methyl-5-β-D-ribofuranosylpyrazine (21 mg, 0.060 mmol) was dissolved in MeOH (3 mL) at RT and the solution cooled to 0° C. PdOH--C was added and the suspension stirred under H2 (g) for 1 h at 0° C. The catalyst was quickly removed by filtration and the product containing solution recovered in a precooled flask. The resulting colorless solution was cooled in N2 (1). Evaporation of the solvent at low temperature under high vacuum yielded 6-amino-3-methyl-5-(β-D-ribofuranosyl)-pyrazin-2-one (18 mg, quant.) as amorphous white solid. Dissolution of the crude product at RT in H2O followed by addition of CH3CN and cooling yielded a few mg of crystalline material. The rest of the material was recovered as amorphous solid after evaporation of the solvent. M.p. 165° C. (dec.); FAB-MS (glycerin): 258 (M+ +1); IR (KBr): 3420 (br.), 3930, 1625 (br.), 1540, 1475, 1375, 1160 (sh), 1075 (br.), 960, 795; 1H-NMR (DMSO): 2.07 (s, 3H, Me-C(3)), 3.40-3.58 (m, 2H, Ha-C(5') and Hb-C(5')), 3.75-3.78 (quadruplettoide m, 1H, H--C(4')), 3.95 (s, very br., 1H, H--C(3')), 4.16-4.17 (quadruplettoide m, 1H, H--C(2')), 4.60 (d, J=6.7, 1H, H--C(1')), 4.75-4.79 (m, 2H, HO--C(2') and HO--C(3')), 5.11-5.13 (triplettoide m, br., 1H, HO--C(5')), 5.79 (s, br. 2H, NH2), 11.1 (s, very br., 1H, NH); 1H-NMR (D2O): 2.19 (s, 3H, Me-C(3)), 3.79 (dd, J=3.4, 12.5, 1H, Ha-C(5')), 3.84 (dd, J=3.0, 12.5, 1H, Hb-C(5')), 4.07 (ddd, J=3.0, 3.4, 3.7, 1H, H--C(4')), 4.25 (dd, J=3.7, 5.8, 1H, H--C(3')), 4.37 (dd, J=5.8, 7.7, 1H, H--C(2')), 4.79 (d, J=7.7, 1H, H--C(1')); 13C-NMR (D2O): 19.91 (q, Me-C(3)), 64.06 (t, C(5')), 73.59, 75.42, 82.94 and 87.69 (d, C(1'), C(2'), C(3') and C(4')), 116.97, 141.05, 145.86 and 160.09 (s, C(2), C(3), C(5) and C(6)); Anal. calc. for C10H15N3O5 (257.25): C 46.69, H 5.88, N 16.33; found: C 46.31, H 5.82, N 15.82.
