Phosphorus-nitrogen compounds. Part 40. The syntheses of (4-fluorobenzyl) pendant armed cyclotetraphosphazene derivatives: Spectroscopic, crystallographic and stereogenic properties, DNA interactions and antimicrobial activities
Gamze Elmas, Aytug Okumus, Zeynel Kiliç, Merve Çam, Leyl Açik, Tuncer Hökelek
Department of Chemistry, Ankara University, 06100 Ankara, Turkey.
The Cl substitution reaction of octachlorocyclotetraphosphazene, N4P4Cl8 (1), with 1.2 equimolar amounts of sodium salt of N/O donor-type bidentate ligand (2) gave four different new (4-fluorobenzyl) pendant armed cyclotetraphosphazene derivatives; namely, mono-(4-fluorobenzyl)-spiro- (spiro; 3), mono-(4-fluorobenzyl)-2-cis-4-dichloro-ansa- (2,4-ansa; 4), bis-(4-fluorobenzyl)-2-trans-6-dispiro (5) and bis-(4-fluorobenzyl)-2-trans-4-dispiro (6) cyclotetraphosphazenes of which 3 was the major product (yield 55%). Compound 3 was treated with mono and difunctional reagents to prepare the fully substituted products (3a-3j) due to its very high yield. However, tetrapyrrolidino-2-cis-4-dichloro-ansa- product (4a) was obtained from the reaction of 2,4-ansa (4) with excess pyrrolidine. The new cyclotetraphosphazenes were characterized by elemental analyses, mass spectrometry (ESI-MS), Fourier transform infrared (FTIR), 1H, 13C, and 31P NMR techniques. The structures of 3 and 3g were determined by X-ray crystallography. 2,4-Ansa compounds (4and 4a) have two stereogenic P atoms. The stereogenic property of 4 was identified by 31P NMR spectra in the addition of the chiral solvating agent, (R)-(+)-2,2,2-trifluoro-1-(9′-anthryl)-ethanol (CSA). The tetraspiro compounds (3i and 3j) look similar to a propeller, and they may have P and M atropisomers. The antimicrobial activities of the compounds were screened against some G(−)/G(+) bacteria and yeast strains. The interactions of the compounds with supercoiled plasmid pBR322 DNA and their inhibited DNA restriction were examined.
Keywords: (4-Fluorobenzyl)cyclotetraphosphazenes, Spectroscopy, Crystallography, Stereogenism, DNA cleavage, Antimicrobial activity.