9-ethylguanine and 9-ethyladenine

The dirhenium complex Re2(i-C3H7COO)4Cl2 was synthesized and characterized by X-ray crystallography, (1)H NMR and electronic spectroscopies, and electrospray ionization-mass spectrometry. The reactions of Re2(i-C3H7COO)4Cl2 with the substituted DNA purine nucleobases guanine (9-methylguanine and 9-ethylguanine) and adenine (9-methyladenine and 9-ethyladenine) were investigated by proton nuclear magnetic resonance and electronic spectroscopies as well as electrospray ionization-mass spectrometry. The data corroborate binding of two 9-methylguanine (or 9-ethylguanine) and 9-methyladenine (or 9-ethyladenine) bases per dirhenium unit in a bidentate fashion, in equatorial positions, via sites N7/O6 and N1/N6, respectively, with concomitant substitution of two carboxylate groups to form a single isomer of cis-Re2(i-C3H7COO)2(nucleobase)2Cl2. The binding of the bases to the dirhenium core disrupts important nucleobase interactions and may have important biological implications with respect to the anticancer activity of dirhenium complexes.

Topics: Adenine; Coordination Complexes; Crystallography, X-Ray; DNA; Guanine; Liposomes; Proton Magnetic Resonance Spectroscopy; Rhenium; Solubility; Spectrometry, Mass, Electrospray Ionization

We show that the binding mode adopted by picolinamide derivatives in organometallic Os(II) and Ru(II) half-sandwich complexes can lead to contrasting cancer cell cytotoxicity. N-Phenyl picolinamide derivatives (XY) in Os(II) (1, 3-5, 7, 9) and Ru(II) (2, 6, 8, 10) complexes [(eta(6)-arene)(Os/Ru)(XY)Cl](n+), where arene = p-cymene (1-8, 10) or biphenyl (9), can act as N,N- or N,O-donors. Electron-withdrawing substituents on the phenyl ring resulted in N,N-coordination and electron-donating substituents in N,O-coordination. Dynamic interconversion between N,O and N,N configurations can occur in solution and is time- and temperature- (irreversible) as well as pH-dependent (reversible). The neutral N,N-coordinated compounds (1-5 and 9) hydrolyzed rapidly (t(1/2) > 4 > 1 > 9). In contrast, N,O-coordinated complexes 7 and 8 hydrolyzed slowly, did not bind to guanine or adenine, and were nontoxic.

Topics: Adenine; Amides; Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; DNA; Guanine; Humans; Hydrogen-Ion Concentration; Hydrolysis; Isomerism; Kinetics; Ligands; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Conformation; Organometallic Compounds; Osmium; Picolinic Acids; Quantum Theory; Ruthenium; Thermodynamics

Proton magnetic resonance was used to study the interactions between nucleosides and phosphate monoanion in dimethyl sulfoxide. Ribose was able to form two mutually exclusive 1:1 complexes involving either OH3' and OH5' or OH3' and OH2' as hydrogen bond donor groups. Deoxyribose could form only one of these complexes. A specific interaction of phosphate with the base moiety of nucleosides was observed only with guanosine. A 1:1 complex was formed involving the N(1)H and NH2(2) of guanine. Association constants for both the base and sugar complexes were determined to be in the range 50-60 M-1 at 21 degrees C in dimethyl sulfoxide. This value is more than 1 order of magnitude higher than that measured for guanine-cytosine base pair formation under the same conditions. Water addition to dimethyl sulfoxide led to a decrease of all association constants but the guanine-phosphate "pair" remained more stable than the guanine-cytosine base pair.

Topics: Adenine; Chemical Phenomena; Chemistry; Deoxyguanosine; Guanine; Guanosine; Hydrogen Bonding; Kinetics; Magnetic Resonance Spectroscopy; Mathematics; Models, Chemical; Phosphates; RNA; Uridine