3-{3,5-Bis[(2-butoxyethoxy)carbonyl]-2,6-dimethyl-1,4-dihydropyridin-4-yl}-1-[(3,4,5-trimethoxybenzoyl)methyl]pyridinium bromide

In the title salt, C37H51N2O10 +·Br−, the 1,4-dihydropyridine (1,4-DHP) ring adopts a slighly puckered boat conformation. The N and opposite C atoms deviate from the least-squares plane calculated through the four other ring atoms by 0.068 (5) and 0.224 (5) Å, respectively. The orientation of both C=O groups is similar (cis with respect to the double bonds of 1,4-DHP. The pyridinium ring has an axial orientation with respect to the1,4-DHP ring and is almost perpendicular to the least-squares plane of the 1,4-DHP ring, making a dihedral angle of 89.2 (3)°. The molecule has a compact shape due to the parallel orientation of the long-chain substituents. One of the butoxy groups was fond to be disordered (occupancy ratio 0.70:0.30). In the crystal, the bromide anion accepts a weak hydrogen bond from the N—H group of a neighboring 1,4-DHP ring.

In the title salt, C 37 H 51 N 2 O 10 + ÁBr À , the 1,4-dihydropyridine (1,4-DHP) ring adopts a slighly puckered boat conformation. The N and opposite C atoms deviate from the least-squares plane calculated through the four other ring atoms by 0.068 (5) and 0.224 (5) Å , respectively. The orientation of both C O groups is similar (cis with respect to the double bonds of 1,4-DHP. The pyridinium ring has an axial orientation with respect to the1,4-DHP ring and is almost perpendicular to the least-squares plane of the 1,4-DHP ring, making a dihedral angle of 89.2 (3) . The molecule has a compact shape due to the parallel orientation of the longchain substituents. One of the butoxy groups was fond to be disordered (occupancy ratio 0.70:0.30). In the crystal, the bromide anion accepts a weak hydrogen bond from the N-H group of a neighboring 1,4-DHP ring.
It was found that the concentration of adenosine, the natural ligand of the A 2A receptor, changes in the ischemia, hypoxia and inflammation conditions (Hasko & Pacher, 2008). The A 2A receptor is believed to play a role in cardioprotection, inflammation, stroke and certain central nervous system disorders (Niebauer & Robinson, 2006). We were looking for molecules based on 1,4-DHP able to bind A 2A adenosine receptors and possessing enhanced water solubility. Fig. 1 shows a view of the crystal structure of the title compound. For the disordered butoxy fragment only atoms with the higher occupation factor are shown. In the crystal structure, the 1,4-DHP ring adopts a slightly puckered boat conformation. Atoms N1 and C4 deviate from the least-squares plane calculated through the four other ring atoms by 0.068 (5) Å and 0.224 (5) Å, respectively. The orientation of both C=O groups is cis with respect to the double bonds of 1,4-DHP. The pyridinium ring has an axial orientation with respect to the 1,4-DHP ring and is almost perpendicular to the least-squares average plane of the 1,4-DHP ring with a dihedral angle between both planes of 89.2 (3)°. The molecule has a compact shape with all long chain substituents oriented approximately in one direction. All bonds in the substituents at the 3 and 5 position of 1,4-DHP have trans orientation except for bonds C29B-C30B and C33-C34 (gauche -). The bromine anion forms a weak hydrogen bond with N1-H1 of a neighboring 1,4-DHP ring. The distance between the bromine ion and the positively charged N2 atom is 4.185 (5) Å.

Experimental
First the DHP 3-pyridyl derivative was obtained by means of the Hantzsch method as described by Saini et al. (2008).

Refinement
The H-atoms were included in the refinement at calculated positions (N-H = 0.86 Å, C-H = 0.93 to 0.98 Å) and treated using a riding-model approximation as implemented in SHELXL97 software. Disorder was detected in the butoxy group with occupancies of 0.7 for atoms C28, C29, C30 and C31 and 0.3 for C28B, C29B, C30B and C31B. The maximum difference density is rather high (1.15 e Å -3 ) because of Fourier series truncation errors expected for a structure containing a heavy atom Br.

Figure 1
The molecular structure of the title compound showing 50% probability elipsoids. No hydrogen atoms shown for clarity.
For the disordered butoxy fragment only atoms with the higher occupation factor are shown (C28 -C31).

3-{3,5-Bis[(2-butoxyethoxy)carbonyl]-2,6-dimethyl-1,4-dihydropyridin-4-yl}-1-[(3,4,5trimethoxybenzoyl)methyl]pyridinium bromide
Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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.

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