6,6′-Di-tert-butyl-4,4′-dimethoxy-2,2′-[1,3-diazinane-1,3-diylbis(methylene)]diphenol 0.19-hydrate

In the title hexahydropyrimidine derivative, C28H42N2O4·0.19H2O, the 1,3-diazinane ring has a chair conformation with a diequatorial substitution. The asymmetric unit contains one half-organic molecule and a solvent water molecule with occupany 0.095. The molecule lies on a mirror plane perpendicular to [010] which passes through the C atoms at the 2- and 5-positions of the heterocyclic system. The partially occupied water molecule is also located on this mirror plane. The dihedral angle between the planes of the aromatic rings is 17.71 (3)°. Two intramolecular O—H⋯N hydrogen bonds with graph-set motif S(6) are present. No remarkable intermolecular contacts exist in the crystal structure.

In the title hexahydropyrimidine derivative, C 28 H 42 N 2 O 4 Á-0.19H 2 O, the 1,3-diazinane ring has a chair conformation with a diequatorial substitution. The asymmetric unit contains one half-organic molecule and a solvent water molecule with occupany 0.095. The molecule lies on a mirror plane perpendicular to [010] which passes through the C atoms at the 2-and 5-positions of the heterocyclic system. The partially occupied water molecule is also located on this mirror plane. The dihedral angle between the planes of the aromatic rings is 17.71 (3) . Two intramolecular O-HÁ Á ÁN hydrogen bonds with graph-set motif S(6) are present. No remarkable intermolecular contacts exist in the crystal structure.
The most obvious difference between the title compound and the related structure (Rivera, et al. 2012a) is the presence of mirror symmetry in the solid state with molecules bisected by mirror planes (the C1 and C2 atoms of the 1,3-diazinane ring lie on the mirror plane). The partially occupied water molecule also is located on this mirror plane. Another important difference is observed in the dihedral angle between the phenyl rings, which is -17.711 (30)° for the title compound and 58.431 (38)° for related structure (Rivera, et al. 2012a). The deviation of the dihedral angle in (I) is probably due to repulsive interactions between the tert-butyl groups. Each channel is composed of two symmetry equivalent positions of the organic molecule. No remarkable intermolecular contacts exist in the presented structure.

Experimental
The title compound was obtained according to our recently reported methodology (Rivera et al., 2012b), that is, to a stirred solution of 2-tert-butyl-4-methoxy-phenol (2.0 mmol) in 96% ethanol (5 ml) heated under reflux, was added slowly a solution of 1, 3,7,9,13,15,19,21-octaazapentacyclo[19.3.1. 13,7 .1 9,13 .1 15,19 ]octacosane prepared according to a previous report (Rivera et al., 2010) (200 mg, 0.54 mmol) in 96% ethanol (5 ml). Upon completion of the addition, the reaction mixture was stirred under reflux for 60 h. Then the reflux was stopped, the solvent was removed on a rotary evaporator under vacuum and the residue obtained was chromatographed on silica gel eluting with benzene/AcOEt (gradient elution with 5% to 20% AcOEt) to afford a solid which was recrystallized in 96% ethanol to provide high quality crystals of the title compound supplementary materials sup-2 Refinement All hydrogen atoms were discernible in difference Fourier maps and could be refined to reasonable geometry. According to common practice the hydrogen atoms attached to carbons were kept in ideal positions with C-H distance 0.96 Å during the refinement. The methyl H atoms were allowed to rotate freely about the adjacent C-C bonds. The coordinates of the hydrogen atom bonded to oxygen were refined freely. All H atoms were refined with displacement coefficients U iso (H) set to 1.5U eq (C, O) for the methyl-and hydroxyl groups and to 1.2Ueq(C) for the CH-, and CH 2 -groups. Fig. 1. A view of (I) with the numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. 6,6'-Di-tert-butyl-4,4'-dimethoxy-2,2'-[1,3-diazinane-1,3-diylbis(methylene)]diphenol 0.19-hydrate
Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F 2 for refinement carried out on F and F 2 , respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement.
The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (