1-Deoxy-1-(4-fluorophenyl)-β-D-ribofuranose, its hemihydrate, and 1-deoxy-1-(2,4-difluorophenyl)-β-D-ribofuranose:: structural evidence for intermolecular C-H•••F-C interactions

The structures of 1-deoxy-1-(4-fluorophenyl)-beta-D-ribofuranose in two crystal forms, (Ia) and (Ib) (C11H13FO4), 1-deoxy-1-(4-fluorophenyl)-beta-D-ribofuranose hemihydrate, (Ic) (C11H13FO4. 0.5H(2)O) and 1-deoxy-1-(2,4-difluorophenyl)-beta-D-ribofuranose, (II) (C11H12F2O4), show two-dimensional networks of intermolecular hydrogen bonds between the hydroxyl groups. Weak intermolecular C-H ... F-C and C-H ...pi(arene) interactions complete the packing in the third dimension. The ribofuranose ring has a conformation intermediate between a C1'-exo,C2'-endo twist and a C2'-endo envelope for (In) and (Ic), a conformation intermediate between a C2'-endo,C3'-exo twist and a C2'-endo envelope for (Ib) and an unsymmetrical C2'-exo,C3'-endo twist conformation for (II).