3-Hydroxy-4-(3-hydroxyphenyl)-2-quinolone monohydrate

In the title compound, also known as viridicatol monohydrate, C15H11NO3·H2O, the dihedral angle between the benzene ring and quinoline ring system is 64.76 (5)°. An intramolecular O—H⋯O hydrogen bond occurs. The crystal structure is stabilized by classical intermolecular N—H⋯O and O—H⋯O hydrogen bonds and weak π–π interactions with a centroid–centroid distance of 3.8158 (10) Å.

In the title compound, also known as viridicatol monohydrate, C 15 H 11 NO 3 ÁH 2 O, the dihedral angle between the benzene ring and quinoline ring system is 64.76 (5) . An intramolecular O-HÁ Á ÁO hydrogen bond occurs. The crystal structure is stabilized by classical intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds and weakinteractions with a centroid-centroid distance of 3.8158 (10) Å .
The 3-hydroxylbenzyl ring subtends a torsion angle of 64.76 (5)° to the quinoline to reduce the steric effect. The structure contains a water molecule which is involved in three out of the six hydrogen bonds formed (Table 1). The whole structure is a 3-D hydrogen-bonding architecture, futther stabilized by the weak π-π interaction between two pyridinone rings with a Cg1···Cg1 (2 -x,1 -y,1 -z) separation of 3.8158 (10) Å and the dihedral angle is zero (where Cg1 is the centroid of the N1/C7-C10/C15). Both weak interactions of hydrogen bonds and π-π effect consolidate the stability of the structure.

Experimental
The fungus phomposis sp was isolated from the mangrove tree, Zhanjiang, and was stored at the Department of Applied Chemistry, Zhongshan University, Guangzhou, China. Starter cultures (from Professor Shining Zhou) were maintained on cornmeal seawater agar. Plugs of agar supporting mycelium growth were cut from solid culture medium and transferred aseptically to a 250 ml Erlenmeyer flask containing 100 ml liquid medium. The fungus was incubated at 28 °C and placed thirty days. The culture was filtered through cheesecloth. The mycelium was air-dried and then extracted in methanol. The CH 3 OH extract of the fungal mycelium was chromatographed on silica gel by using a gradient from petroleum to ethyl acetate, then from acetate to methanol, and obtained viridicatol eluted with 50% ethyl acetate-petroleum ether. Colorless block crystals were grown from a solution in methanol at room temperature over several days.
supplementary materials sup-2 Refinement H atoms bonded to C atoms were positioned geometrically and treated as riding, with C-H distances of 0.93 Å and U iso (H)=1.2U eq (C). H atoms involved in hydrogen-bonding interactions (water, pyridinone, and hydroxy) were located from difference Fourier maps, idealized and refined with a riding scheme. Fig. 1. The molecular structure of (I), with atom labels and 30% probability displacement ellipsoids for non-H atoms. The hydrogen bonds are shown as dashed lines.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 Rfactors(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.