Spectroscopic characterization and molecular structure of 3,14-dimethyl-2,6,13,17-tetraazapentacyclo[16.4.0.12,17.16,13.07,12]tetracosane

Abstract

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[16.4.0.12,17.16,13.07,12]tetracosane macrocycle, C22H40N4, is reported. Formaldehyde reacts readily at room temperature with the tetraazatricyclo[16.4.0.02,17]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 atransconformation 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.