Phosphorus–Nitrogen Compounds. Part 24. Syntheses, Crystal Structures, Spectroscopic and Stereogenic Properties, Biological Activities, and DNA Interactions of Novel Spiro-ansa-spiro- and Ansa-spiro-ansa-cyclotetraphosphazenes

The reactions of octachlorocyclotetraphosphazene,
N4P4Cl8, with N2O2 donor-type
aminopodands (1a, 1b, 1g, and 1h) afforded two kinds of derivatives, namely, spiro-ansa-spiro
(sas) (2a, 2b, 2g, and 2h) and ansa-spiro-ansa (asa) (3a and 3b) phosphazenes. The partly substituted sas phosphazenes (2a and 2b) reacted
with excess pyrrolidine and morpholine in tetrahydrofuran to produce
the tetrapyrrolidino (2c and 2d) and morpholino
(2e and 2f) derivatives. The reactions of
the asa phosphazenes (3a and 3b) with excess pyrrolidine and morpholine produced gem-2-trans-6-dichloropyrrolidinophosphazenes (3c and 3d) and -morpholinophosphazenes (3e and 3f). However, the fully substituted products
were not obtained in these solvents. In addition, the expected fully
substituted compound was not obtained from the reaction of 3a with excess pyrrolidine by standard or microwave-assisted methods.
The reaction of the long-chain starting compound (1g)
with N4P4Cl8 gave sas (2g) and the interesting 2,6-ansa-spiro-bicyclo product
(bicyclo-2,6-as; 4g), while the reaction
of 1h with N4P4Cl8 yielded
only sas (2h). The structural investigations
of the compounds were verified by elemental analyses, mass spectrometry,
Fourier transform infrared, and DEPT, HSQC, HMBC, 1H, 13C, and 31P NMR techniques. The crystal structures
of 2b, 3a, 3b, 3e, and 4g were determined by X-ray crystallography. Compounds 2a–2h, 3a–3f, and 4g had two stereogenic P atoms. Compound 3b had one enantiomer according to the Flack parameter, and 3f was a racemic mixture, as shown by chiral high-performance
liquid chromatography and chiral-solvating-agent, (R)-(+)-2,2,2-trifluoro-1-(9′-anthryl)­ethanol, experiments.
Furthermore, compounds 2a, 2c, and 2d exhibited weak antibacterial activity against (G+) bacterium,
and 3c and 3d displayed moderate antifungal
activity against Candida tropicalis. Gel electrophoresis
data demonstrated that 2e, 3c, and 3e promoted the formation of DNA cleavage. The prevention
of BamHI digestion by 2a–2f and 3a–3f, except 2b and 2e, disclosed binding with GG nucleotides
in DNA.

八氯环四磷腈（octachlorocyclotetraphosphazene, N4P4Cl8）与N2O2给体型氨基穴状配体（aminopodands，1a、1b、1g及1h）发生反应，得到两类衍生物：螺-桥连-螺（spiro-ansa-spiro, sas，2a、2b、2g及2h）型与桥连-螺-桥连（ansa-spiro-ansa, asa，3a及3b）型磷腈化合物。部分取代的sas型磷腈（2a与2b）在四氢呋喃（tetrahydrofuran）中与过量吡咯烷（pyrrolidine）和吗啉（morpholine）反应，生成四吡咯烷取代（2c与2d）及四吗啉取代（2e与2f）衍生物。asa型磷腈（3a与3b）与过量吡咯烷和吗啉反应，得到gem-2-反式-6-二氯吡咯烷取代磷腈（3c与3d）及吗啉取代磷腈（3e与3f），但在上述溶剂中均未分离得到全取代产物。此外，通过常规法或微波辅助法使3a与过量吡咯烷反应，同样未获得预期的全取代化合物。长链起始配体1g与N4P4Cl8反应，得到sas型产物2g与新型2,6-桥连-螺双环产物（bicyclo-2,6-as; 4g）；而配体1h与N4P4Cl8反应仅得到sas型产物2h。通过元素分析、质谱法、傅里叶变换红外（Fourier transform infrared）光谱，以及DEPT、HSQC、HMBC、1H、13C及31P核磁共振波谱技术对所有目标化合物的结构进行了表征与验证。采用X射线晶体学（X-ray crystallography）测定了化合物2b、3a、3b、3e及4g的晶体结构。化合物2a~2h、3a~3f及4g均含有两个手性磷原子。根据弗莱克参数（Flack parameter），化合物3b为单一对映异构体；通过手性高效液相色谱（chiral high-performance liquid chromatography）与手性溶剂化试剂(R)-(+)-2,2,2-三氟-1-(9'-蒽基)乙醇（(R)-(+)-2,2,2-trifluoro-1-(9′-anthryl)ethanol）实验证实，化合物3f为外消旋混合物。此外，化合物2a、2c及2d对革兰氏阳性（G+）细菌表现出弱抗菌活性，化合物3c与3d对热带假丝酵母（Candida tropicalis）显示出中等抗真菌活性。凝胶电泳（gel electrophoresis）数据表明，化合物2e、3c及3e可促进DNA切割反应的发生。除2b与2e外，化合物2a~2f与3a~3f均可抑制BamHI限制性内切酶对DNA的消化，说明其可与DNA中的GG核苷酸结合。