NMR conformational analysis of p-tolyl furanopyrimidine 2′-deoxyribonucleoside and crystal structure of its 3′,5′-di- O-acetyl derivative

Abstract

The conformation of a representative molecule of a new, potent class of antiviral-active modified nucleosides is determined. A bicyclic nucleoside, 3-(2′-deoxy-β- d-ribofuranosyl)-6-(4-methylphenyl)-2,3-dihydrofuro[2,3- d]pyrimidin-2-one, shows C2′- endo and C3′- endo ribose conformations in solution (63:37, 37 °C; DMSO- d 6), as determined by 1H NMR studies. The crystal structure of a 3′,5′-di- O-acetyl-protected derivative (monoclinic, P2 1, a/ b/ c = 6.666(1)/12.225(1)/24.676(2) Å, β = 90.24(1)°, Z = 4) shows exclusively C2′- endo deoxyribose puckering. The base is found in the anti position both in solution and in crystalline form.