Spectroscopic characterization and molecular structure of 3,14-dimethyl-2,6,13,17-tetraazapentacyclo[16.4.0.1(2,17).1(6,13).0(7,12)]tetracosane.

Constrained cyclam derivatives have been found to exhibit anti-HIV effects. The strength of binding to the CXCR4 receptor correlates with anti-HIV activity. The conformation of the macrocyclic compound is very important for co-receptor recognition. Therefore, knowledge of the conformation and crystal packing of macrocycles has become important in developing new highly effective anti-HIV drugs. Structural modifications of N-functionalized polyaza macrocyclic compounds have been achieved using various methods. A new synthesis affording single crystals of the title tetraazapentacyclo[16.4.0.1(2,17).1(6,13).0(7,12)]tetracosane macrocycle, C22H40N4, is reported. Formaldehyde reacts readily at room temperature with the tetraazatricyclo[16.4.0.0(2,17)]docosane precursor to yield a macropolycycle containing two five-membered rings. Characterization by elemental, spectroscopic and single-crystal X-ray diffraction analyses shows that the asymmetric unit contains half of a centrosymmetric molecule. The molecular structure shows a trans conformation for the two methylene bridges owing to molecular symmetry. The crystal structure is stabilized by intramolecular C-H...N hydrogen bonds. NMR and IR spectroscopic properties support the methylene-bridged macrocyclic structure.