Phosphorus-nitrogen compounds. Part 56. Comparative syntheses and spectral properties of multiheterocyclic 2-cis-4-ansa and spiro-ferrocenyl (N/O)cyclotetraphosphazenes: Antituberculosis and antimicrobial activity and DNA interaction studies

Abstract In the present study, two types of starting compounds; hexachloro(N/O)-cyclotetraphosphazenes containing mono-ferrocenyl-pendant arm, namely, mono-ferrocenyl-2-cis-4-dichloro-ansa-(2,4-ansa; 2) and mono-ferrocenyl-spiro-(spiro; 3) were prepared by the reaction of N4P4Cl8 (1) with sodium 3-(N-ferrocenylmethylamino)-1-propanoxide (L). Reactions of 2,4-ansa (2) with excess benzylamine and n-hexylamine resulted in the formation of partly substituted 2-cis-4-dichloro-ansa-cyclotetraphosphazenes (2a and 2b). In contrast, spiro (3) gave fully substituted mono-ferrocenyl-spiro-cyclotetraphosphazenes (3a and 3b) with excess benzylamine and n-hexylamine. As expected, the 2,4-ansa cyclotetraphosphazenes (2, 2a, and 2b) have two distinct stereogenic P-centers. The structures of cyclotetraphosphazenes were evaluated by elemental analysis, ESI-MS, FTIR, 1H, 13C, and 31P-NMR techniques. The antibacterial and antifungal activities against some selected bacteria and yeast strains, antituberculosis activities against Mycobacterium tuberculosis H37Rv, and DNA cleavage activities of mono-ferrocenyl-cyclotetraphosphazenes were also discussed. Compounds 2b, 3a, and 3b exhibited antifungal activity against C. albicans (MIC= 156.3 µM) higher than reference antibiotic Ketoconazole. Moreover, four compounds displayed antituberculosis activity against the M. tuberculosis H37RV. Compound 2a (20 μg/mL) is the most potent of the four compounds. Graphical abstract