Novel quinoxaline 1,4-di-N-oxide derivatives as new potential antichagasic agents.

As a continuation of our research and with the aim of obtaining new agents against Chagas disease, an extremely neglected disease which threatens 100 million people, eighteen new quinoxaline 1,4-di-N-oxide derivatives have been synthesized following the Beirut reaction. The synthesis of the new derivatives was optimized through the use of a new and more efficient microwave-assisted organic synthetic method. The new derivatives showed excellent in vitro biological activity against Trypanosoma cruzi. Compound 17, which was substituted with fluoro groups at the 6- and 7-positions of the quinoxaline ring, was the most active and selective in the cytotoxicity assay. The electrochemical study showed that the most active compounds, which were substituted by electron-withdrawing groups, possessed a greater ease of reduction of the N-oxide groups.

Nine compounds containing high-nuclearity [Cu(n)X(2n+2)]2- (n = 4, 5 or 7; X = Cl or Br) quasi-planar oligomers.

The structures of seven A(2)Cu(4)X(10) compounds containing quasi-planar oligomers are reported: bis(1,2,4-trimethylpyridinium) hexa-µ-chlorido-tetrachloridotetracuprate(II), (C(8)H(12)N)(2)[Cu(4)Cl(10)], (I), and the hexa-µ-bromido-tetrabromidotetracuprate(II) salts of 1,2,4-trimethylpyridinium, (C(8)H(12)N)(2)[Cu(4)Br(10)], (II), 3,4-dimethylpyridinium, (C(7)H(10)N)(2)[Cu(4)Br(10)], (III), 2,3-dimethylpyridinium, (C(7)H(10)N)(2)[Cu(4)Br(10)], (IV), 1-methylpyridinium, (C(6)H(8)N)(2)[Cu(4)Br(10)], (V), trimethylphenylammonium, (C(9)H(14)N)(2)[Cu(4)Br(10)], (VI), and 2,4-dimethylpyridinium, (C(7)H(10)N)(2)[Cu(4)Br(10)], (VII). The first four are isomorphous and contain stacks of tetracopper oligomers aggregated through semicoordinate Cu···X bond formation in a 4(5/2,1/2) stacking pattern. The 1-methylpyridinium salt also contains oligomers stacked in a 4(5/2,1/2) pattern, but is isomorphous with the known chloride analog instead. The trimethylphenylammonium salt contains stacks of oligomers arranged in a 4(3/2,1/2) stacking pattern similar to the tetramethylphosphonium analog. These six structures feature inversion-related organic cation pairs and hybrid oligomer/organic cation layers derived from the parent CuX(2) structure. The 2,4-dimethylpyridinium salt is isomorphous with the known (2-amino-4-methylpyridinium)(2)Cu(4)Cl(10) structure, in which isolated stacks of organic cations and of oligomers in a 4(1/2,1/2) pattern are found. In bis(3-chloro-1-methylpyridinium) octa-µ-bromido-tetrabromidopentacuprate(II), (C(6)H(7)ClN)[Cu(5)Br(12)], (VIII), containing the first reported fully halogenated quasi-planar pentacopper oligomer, the oligomers stack in a 5(3/2,1/2) stacking pattern as the highest nuclearity [Cu(n)X(2n+2)](2-) oligomer compound known with isolated stacking. Bis(2-chloro-1-methylpyridinium) dodeca-µ-bromido-tetrabromidoheptacuprate(II), (C(6)H(7)ClN)(2)[Cu(7)Br(16)], (IX), contains the second heptacopper oligomer reported and consists of layers of interleaved oligomer stacks with a 7[(7/2,1/2)][(-9/2,-1/2)] pattern isomorphous with that of the known 1,2-dimethylpyridinium analog. All the oligomers reported here are inversion symmetric.