1-Cyclohexyl-2-(3-furyl)-1H-benzimidazole-5-carboxylic acid

The asymmetric unit of the title compound, C18H18N2O3, contains two molecules. The fused rings of both molecules are almost planar, with dihedral angles of 3.1 (1) and 2.8 (2)° between the fused rings. The furan rings are rotated by 43.85 (15) and −21.07 (9)° with respect to the planes of the attached bnzimidazole systems. In the crystal, molecules are linked into infinite chains by intermolecular O—H⋯N hydrogen bonds.


Comment
The title compound is an allosteric inhibitor of the RNA-dependent RNA polymerase NS5B of hepatitis C virus (HCV) (Beaulieu et al., 2004a). The inhibitor binds with low micromolar affinity (4.3 mM) to the NS5B polymerase and prevents replication of subgenomic HCV replicon in human cells (Beaulieu et al., 2004b). The title compound was synthesized following the route described by Beaulieu et al., (2004b). We report here the single-crystal X-ray structure.
Upon slow evaporation at 273 K within 2 months the crystals are formed as colourless blocks.

Refinement
Acidic H2 and H4 hydrgen atoms were located in a Fourier difference map and refined freely with distances obtained for O2-H2 = 1.00 (5) and O4-H4 = 0.76 (5). Other H atoms were positioned geometrically and refined using a riding model with C-H = 0.95-0.99 Å and with U iso (H) = 1.2 U eq (C).
The highest density value is peak with a value of 0.73 e Å -3 at coordinates 0.5281 0.1307 0.9370 that is 1.21Å from atom H6 and 1.24Å from atom C17.
1455 Friedel pairs were merged. Fig. 1. The asymmetric units of structure of title compound, with the atom-numbering scheme. The displacement ellipsoids are drawn at 50% probability level. H atoms are presented as a small spheres of arbitrary radius. Fig. 2. The crystal packing of one of the two molecules, viewed down the a axis, showing the molecules are linked along the b axis. Intermolecular hydrogen bonds are shown as dashed lines. Symmetry codes: (i) -x + 1, y + 1/2, -z + 1 and (ii) -x + 1, y -1/2, -z + 1. Second molecule behaves similarly.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.