corrole and pyridine

G-quadruplex DNA plays an important role in the potential therapeutic target for the design and development of anticancer drugs. As various G-quadruplex sequences in the promoter regions or telomeres can form different secondary structural modes and display a diversity of biology functions, variant G-quadruplex interactive agents may be necessary to cure different disease by differentiating variant types of G-quadruplexes. We synthesize five cationic methylpyridylium corroles and compare the interactions of corroles with different types of G-quadruplexes such as cmyc, htelo, and bcl2 by using surface plasmon resonance. Because of the importance of human telomere G-quadruplex DNA, we focus on the biological properties of the interactions between human telomere G-quadruplex DNA and corrole isomers using CD, T(m), PCR-stop (PCR= polymerase chain reaction), and polymerase-stop assay, which demonstrate the excellent ability of the corrole to induce and stabilize the G-quadruplex. This study provides the first experimental insight into how selectivity might be achieved for different G-quadruplexes by a single group of methylpyridylium corrole isomers that may be optimized for potential selective cancer therapy.

Topics: Antineoplastic Agents; Circular Dichroism; G-Quadruplexes; Isomerism; Kinetics; Porphyrins; Pyridines; Surface Plasmon Resonance; Telomerase; Transition Temperature

Several procedures for the demetalation of silver(III) corrolates have been tested. Acidic conditions induce removal of the silver ion but they can also promote concomitant oxidation of the corrole nucleus to an isocorrole species, the degree of which will depend upon the specific acidic media. This oxidation cannot be completely avoided by addition of hydrazine, particularly in the case of 3-NO(2) substituted complexes which are quantitatively converted into the corresponding 3-NO(2), 5-hydroxy isocorroles upon silver ion removal. Several beta-nitro isocorrole products were isolated, and one was structurally characterized. Electrochemical and chemical reductive methods for silver(III) corrolates demetalation were then tested with the aim to avoid the formation of isocorroles. While reaction with sodium borohydride was shown to be quite effective to demetalate unsubstituted silver corrolates this was not the case for the beta-nitro derivatives where the peripheral nitro group is reduced by borohydride giving the corresponding 3-amino free base corrole species. For the beta-nitro corrole silver complexes, a successful approach was obtained using DBU/THF solutions which afforded the 3-NO(2) corrole free-base compound as a single reaction product in good yield. These conditions were also effective for unsubstituted corroles although longer reaction times were necessary in this case. To study in greater detail the corrole demetalation behavior, selected Ag(III) derivatives were characterized by cyclic voltammetry in pyridine, and the demetalation products spectrally characterized after controlled potential reduction in a thin-layer spectroelectrochemical cell.

Topics: Coordination Complexes; Crystallography, X-Ray; Electrochemistry; Models, Molecular; Porphyrins; Pyridines; Silver