Syntheses, spectroscopic properties, crystal structures, biological activities, and DNA interactions of heterocyclic amine substituted spiro-ansa-spiro- and spiro-bino-spiro-phosphazenes

The heterocyclic amine e.g. pyrrolidine, piperidine, morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD) substituted spiro-ansa-spiro (sas) 5a–5d and spiro-bino-spiro (sbs) 6a–6d phosphazenes were prepared by the replacement reactions of the Cl-atoms in 3 and 4 with heterocyclic amines in dry THF (Scheme 1). All of the phosphazene derivatives were characterized by elemental analysis, FTIR, MS, 1D 1H, 13C and 31P NMR and DEPT and 2D HSQC techniques. The crystal structures of fully morpholine substituted sas 5c and sbs 6c phosphazenes were verified by X-ray diffraction analysis. The relationships between exocyclic OPN bond angles (α′) and δPOPN shifts, and the correlation of Δ(P–N) values and Δ(δP) or δPOPN shifts were presented. The phosphazene derivatives (3, 4, 5a–5d and 6a–6d) were subjected to antimicrobial activity against six pathojen bacteria and two yeast strains. Fully pyrrolidine substituted sbs 6a was found to be quite active against yeast strain Candida tropicalis. In addition, the nature of the interactions of these compounds with pBR322 plasmid DNA was investigated, and the results displayed that partly substituted sas 3 and sbs 4 caused to cleave the DNA.