Synthesis Of A Novel Cationic Triazatetrabenzcorrole Derivative And Its Application In Hg²⁺ Detection; Synthesis Of Dithienylethene Derivative

The G-rich DNA sequences can form the G-quadruplex structure via the Hoogsteen hydrogen bond between guanines. These G-rich DNA sequences were widely exist in telomeres, immunoglobulin gene switch region and gene promoters, which are genomic regions. The given DNA sequences can form G-quadruplex in vitro, which suggests G-quadruplex may possess vital biological functions. Research showed that some small organic molecules may block telomerase activities by stabiling the G-quadruplex structure. Therefore, these G-quadruplex ligands can be used as candidates of anti-cancer drugs.There are many type of G-quadruplex stabilizer, including porphyrin, phthalocyanine and corrole, which are tetrapyrrolic macrocycle compounds. In this thesis, two cationic triazatetrabenzcorrole derivatives 4 and 8 were designed and synthesized, which were used as G-quadruplex stabilizer. Triazatetrabenzcorroles are phthalocyanine-like compounds that have lost a bridging nitrogen atom. We use 'HNMR,'H-'H COSY,31PNMR, HRMS and infrared spectra to characterize their structure.When we use CD spectroscopy to test the ability of compound 4 to stabilize G-quadruplex, we find that it can not induce telomeric sequence to form G-quadruplex structure, and the original objective is therefore not reached. Compound 4, however, as we discovered it, can be induced to aggregate by polyanions or single stranded DNA, which results in fluorescence quenching. So we design a functional nucleic acid sensor to detect Hg2+ cation based on such feature of compound 4. In the test, we adopt a sulfo-modified DNA strand, T4G4-S3(TPsTPSTPSTGGGG), which forms parallel G-quadruplex in the existence of Hg2+. The whole detection system contains compound 4 and T4G4-S3. Given the absence of Hg2+, T4G4-S3 appear as single stranded form, capable of inducing compound 4 to aggregate, causing fluorescence quenching, In contrast, as Hg2+ was added, T4G4-S3 transform into G-quadruplex structure, which is incapable of inducing aggregation, and fluorescence of compound 4 is not quenching. Comparing the fluorescence elevation of these two tests, we are able to quantitatively detect the Hg2+, and the detection limit is 10 nM.Photochromism is the reversible transformation of a compound between two forms by the irradiation of light at a certain wavelength, where the two forms have different colors, absorption spectra and chemical properties. Using rational design and molecular modeling methods, we have designed and synthesized a photochromic dithienylethene derivative 14. This compound can form planus closed-ring structure under the UV irradiation while it form non-planar open ring structure under natural light exposure. Because the bind ability to G-quadruplex of these two forms of compound 14, we are able to photoregulate the G-quadruplex conformation. This paper complete the synthesis of compound 14, the photoregulation of G-quadruplex conformation requires further research.