Phosphorus-nitrogen compounds. Part 40. The syntheses of (4-fluorobenzyl) pendant armed cyclotetraphosphazene derivatives: Spectroscopic, crystallographic and stereogenic properties, DNA interactions and antimicrobial activities

Abstract

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 (4 and 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.