- Synthesis of 2,2′-bis(3,6,9-triazanonyl)-4,4′-bithiazole and related compounds as new DNA cleavage agents
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Two new bithiazole derivatives, 2,2′-bis(3,6,9-triazanonyl)- and 2,2′-bis(3,7,11-triazaundecyl)-4,4′-bithiazoles (3a, b), were readily synthesized in six steps using the corresponding dialkylenetriamine as starting materials. Under physiological conditions, 5.0 μM 3a exhibited significant DNA cleavage activity in the presence of Co(II), whereas even at 50 μM, 3b exhibited no DNA cleavage activity. Furthermore, it was demonstrated that 3a forms a 1 : 2 complex with Co(II) ions, whereas 3b does not. These conclusions were based on measurements of stoichiometries of the bithiazole-cobalt complexes obtained by the Job continuous variation method. In contrast, 3a, which contains diethylenetriamine moieties, showed decreased affinity for Calf Thymus (CT) DNA compared with that of 3b, which contains dipropylenetriamine moieties. These findings indicate that the structure of the two aminoalkyl side chains attached at the 2- and 2′-positions of the 4,4′-bithiazole ring significantly influence the formation of cobalt complexes, and affects the compound's ability to cleave DNA as well as its affinity for double-stranded DNA.
- Sasaki, Hideaki
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- Quinquedentate Co-ordination of Amino-substitiuted Tetraazacycloalkanes to Co(III). Part 3. Synthesis of an Unsymmetric Ligand and Crystal Structure of its cis-Chlorocobalt(III) Complex
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The unsymmetric pendant-arm macrocycle 9-methyl-9-nitro-1,4,7,11-tetraazacyclotetradecane (L1) was prepared by a copper(II)-directed condensation of 3,6-diaazanonan-1,9-diamine with nitroethane and formaldehyde.Reduction of the copper(II) complex of (L1) with zinc in aqueous acid produced the new potentially quinquedentate polyamine 9-methyl-1,4,7,11-tetraazacyclotetradecan-9-amine (L2).Reaction of L2 in water with cobalt(II) ion and air, followed by aqueous hydrochloric acid and equilibration with activated charcoal, yielded exclusively cis-2(Cl)>2 which crystallized in the monoclinic space group P21/c, with a = 12.745(5), b = 11.438(5), c = 14.414(8) Angstroem and β = 104.80(3) deg.The pendant primary amine and two adjacent secondary amines necessarily occupy an octahedral face, with the chloro ligand cis to the primary amine, and secondary amines adopt RRSS stereochemistries.The average Co-N distance is 1.96(0) Angstroem, and the Co-Cl distance is 2.252(1) Angstroem.Stereoretentive base hydrolysis (k(OH) 9100 dm3 mol-1 s-1) and other structural and physical properties are compared with those of the symmetric analogue 6-methyl-1,4,8,11-tetraazacyclotetradecan-6-amine.
- Lawrance, Geoffrey A.,Martinez, Manuel,Skelton, Brian W.,White, Allan H.
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