(3E,5E)-3,5-Bis(4-hy-droxy-3,5-di-methoxy-benzyl-idene)oxan-4-one monohydrate.

In the title compound, C(23)H(24)O(8)·H(2)O, the six-membered ring of the oxan-4-one (tetra-hydro-pyran-4-one) ring displays an envelope conformation with the heterocyclic O atom at the flap position. The dihedral angles between the terminal benzene rings is 37.23 (10)°. Classical intermolecular O-H⋯O and weak C-H⋯O hydrogen bonds are present in the crystal structure.

In the title compound, C 23 H 24 O 8 ÁH 2 O, the six-membered ring of the oxan-4-one (tetrahydropyran-4-one) ring displays an envelope conformation with the heterocyclic O atom at the flap position. The dihedral angles between the terminal benzene rings is 37.23 (10) . Classical intermolecular O-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds are present in the crystal structure.
The molecular structure of the title compound contains the two 4-hydroxy-3,5-dimethoxyphenyl substituents on the tetrahydropyran-4-one, and the six-membered hetero-ring adopts an envelope conformation with the flap oxygen atom displaced by 0.682 (10) Å from the plane of the other five atoms ( Figure 1). Similar structures have been observed in the literature (Abaee et al., 2008;Du et al., 2006a,b).
In the crystal packing, the molecules are linked by intermolecular O-H···O hydrogen bonds into one-dimensional zigzag chain along b axis ( Figure 2, table 1), and through water molecules further connecting into a supramolecular three-dimensional complicated hydrogen bonding network ( Figure 3, table 1).

Experimental
The title compound was synthesized using a general procedure (Du et al., 2006a,b;Youssef et al., 2004). 4-Hydroxy-3,5dimethoxybenzy (0.01 mol) and tetrahydropyran-4-one (0.005 mol) were dissolved in THF and added 0.5 mL concentrated HCl as catalyst. The mixture was warmed at 298-303 K for 24 h, cold water was added to precipitate the yellow compound.
Crystals were obtained by recrystallization from THF solution.
(3E,5E)-3,5-Bis(4-hydroxy-3,5-dimethoxybenzylidene)oxan-4-one monohydrate  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 > 2sigma(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.