V. R. S. Malta

1,3-Azoles from ortho-naphthoquinones: synthesis of aryl substituted imidazoles and oxazoles and their potent activity against Mycobacterium tuberculosis.

Twenty-three naphthoimidazoles and six naphthoxazoles were synthesised and evaluated against susceptible and rifampicin- and isoniazid-resistant strains of Mycobacterium tuberculosis. Among all the compounds evaluated, fourteen presented MIC values in the range of 0.78 to 6.25 μg/mL against susceptible and resistant strains of M. tuberculosis. Five structures were solved by X-ray crystallographic analysis. These substances are promising antimycobacterial prototypes.

1,2-Dihydr-oxy-2-(3-methyl-but-2-en-yl)-3-oxo-2,3-dihydro-1H-indene-1-carboxylic acid monohydrate.

The title compound, C15H16O5·H2O, is an intermediate of the Hooker oxidation reaction, used for the synthesis of 2-hydroxy-3-(2-methylprop-1-enyl)naphthalene-1,4-dione (nor-lapachol). The packing in the crystal structure is arranged by an O—H⋯O hydrogen-bonded network along the [100] and [010] directions. Each organic molecule is linked to four other molecules via the hydroxy groups. The water solvent molecule is connected to carboxylic acid groups by three hydrogen bonds.

Structural isomerism of Ru(II)-carbonyl complexes: synthesis, characterization and their antitrypanosomal activities

New complexes with the general formula [RuCl(CO)(dppb)(diimine)]PF6, [dppb = 1,4-bis(diphenylphosphino)butane; diimine = 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen)], were prepared. Thus, the complexes ct-[RuCl(CO)(dppb)(bipy)]PF6 (1), ct-[RuCl(CO)(dppb)(phen)]PF6 (2), tc-[RuCl(CO)(dppb)(bipy)]PF6 (3), tc-[RuCl(CO)(dppb)(phen)]PF6 (4), cc-[RuCl(CO)(dppb)(bipy)]PF6 (5) and cc-[RuCl(CO)(dppb)(phen)]PF6 (6) were obtained and characterized. In this case, the first letter in the prefixes indicates the position of CO with respect to the chlorido ligand and the second one is related to the phosphorus atoms. The compositions of the complexes were confirmed by analytical techniques and an octahedral environment around the ruthenium was confirmed by single-crystal X-ray diffraction of the complexes ct-[RuCl(CO)(dppb)(bipy)]PF6 and cc-[RuCl(CO)(dppb)(phen)]PF6. The oxidation potentials of the complexes were determined by cyclic voltammetry and it was found that they vary according to the CO position in the complexes. In order to obtain information on the stability of the ct, tc and cc-[RuCl(CO)(dppb)(bipy)]PF6 (1), (3) and (5) isomers, computational studies were carried out, and they showed large differences between the HOMO/LUMO energies. As monitored by 13C NMR, the stability of the complexes with respect to CO displacement, for at least 72 h, in DMSO-d6 solution, is independent of the CO position in the complexes. Pharmacological evaluation of the complexes against the Trypanosoma cruzi parasite revealed the structure–activity relationships, showing that the presence and position of the CO ligand in the complexes are relevant for the antiparasitic activity of the compounds. The most active compound, the tc-[RuCl(CO)(dppb)(bipy)]PF6 isomer, presented potent antiparasitic activity, which was achieved by causing oxidative stress followed by parasite cell death through necrosis. Thus, the findings presented here demonstrate that the use of a carbonyl ligand provides stability and pharmacological properties to ruthenium/diphosphine/diimine complexes.

1,4- Addition of diazomethane to a heterodiene: a direct preparation of the oxazolic ring

The reaction of naphthoquinone-oximes (3) and (4) with diazomethane yields directly, in one step, the oxazoles (5) and (6), respectively.

Different coordination modes for disulfoxides towards diorganotin(IV) dichlorides. X-ray crystal structures of 1,2-cis-bis-(phenylsulfinyl)ethene (rac-,cis-cbpse) and adducts [{Ph2SnCl2(meso-bpse)}n] and [{n-Bu2SnCl2(pdtd)}2]

The reactions of meso-1,2-bis(phenylsulfinyl)ethane (meso-bpse) with Ph2SnCl2, 2-phenyl-1,3-dithiane trans-1-trans-3-dioxide (pdtd) with n-Bu2SnCl2 and 1,2-cis-bis-(phenylsulfinyl)ethene (rac-,cis-cbpse) with Ph2SnCl2, in 1:1 molar ratio, yielded [{Ph2SnCl2(meso-bpse)}n], [{n-Bu2SnCl2(pdtd)}2] and [{Ph2SnCl2(rac,cis-cbpse)}x] (x = 2 or n), respectively. All adducts were studied by IR, Mossbauer and 119Sn NMR spectroscopic methods, elemental analysis and single crystal X-ray diffractometry. The X-ray crystal structure of [{Ph2SnCl2(meso-bpse)}n] revealed the occurrence of infinite chains in which the tin(IV) atoms appear in a distorted octahedral geometry with Cl atoms in cis and Ph groups in trans positions. The X-ray crystal structure of [{n-Bu2SnCl2(pdtd)}2] revealed discrete centrosymmetric dimeric species in which the tin(IV) atoms possess a distorted octahedral geometry with bridging disulfoxides in cis and n-butyl moieties in trans positions. The spectroscopic data indicated that the adduct containing the rac,cis-cbpse ligand can be dimeric or polymeric. The X-ray structural analysis of the free rac-,cis-cbpse sulfoxide revealed that the crystals belong to the C2/c space group.

trans-5,6-Diphenyl­perhydro­pyran-2,4-dione

In the title compound, C17H14O3, the pyran ring adopts a boat conformation and the dihedral angle between the aromatic ring planes is 59.1 (1)°. In the crystal structure intermolecular C—H⋯O hydrogen bonds and C—H⋯π interactions link the molecules.

3-Bromo-β-lapachone

In the title compound, C15H13BrO3, the benzo and quinone rings are planar, while the heterocycle is in a distorted half-chair conformation.

Palladium-benzodiazepine derivatives as promising metallodrugs for the development of antiepileptic therapies.

We synthesized two organometallic diazepam-palladium(II) derivatives by C-H activation of diazepam (DZP) with palladium salts, i.e., PdCl2 and Pd(OAc)2 (OAc=acetate). Both compounds obtained are air stable and were isolated in good yields. The anticonvulsant potential of the complexes, labeled [(DZP)PdCl]2 and [(DZP)PdOAc]2, was evaluated through two animal models: pentylenetetrazole (PTZ)- and picrotoxin (PTX)-induced convulsions. The organometallic DZP-palladium(II) acetate complex, [(DZP)PdOAc]2, significantly increased (p<0.01 or p<0.001) latencies and protected the animals against convulsions induced by PTZ and PTX, while the analogous chloro derivative, [(DZP)PdCl]2, was effective (p<0.01) only in the PTZ model. These effects appear to be mediated through the GABAergic system. The possible mechanism of action of the DZP-palladium(II) complexes was also confirmed with the use of flumazenil (FLU), a GABAA-benzodiazepine receptor complex site antagonist. Herein, we present the first report of the anticonvulsant properties of organometallic DZP-palladium(II) complexes as well as evidence that these compounds may play an important role in the study of new drugs to treat patients with epilepsy.

cis-Bis(1,10-phenanthroline-κ2N,N′)bis­(pyridin-4-amine-κN1)ruthenium(II) bis­(hexa­fluoridophosphate)

In the title complex, [Ru(C12H8N2)2(C5H6N2)2](PF6)2, the RuII atom is bonded to two α-diimine ligands, viz. 1,10-phenanthroline (phen), in a cis configuration, in addition with with two 4-aminopyridine (4Apy) ligands, resulting in a distorted octahedral coordination geometry. N—H⋯F hydrogen-bonding interactions play an important role in the crystal assembly: 21-screw-axis-related complex molecules and PF6 − counter-ions alternate in helical chains formed along the a axis by means of these contacts. N—H⋯π contacts (H⋯centroid = 3.45 Å) are responsible for cross-linking between the helical chains along [001].

cis-Bis(2,2′-bipyridine-κ2N,N′)bis­(pyridin-4-amine-κN1)ruthenium(II) bis­(hexa­fluoridophosphate) acetonitrile monosolvate

In the title complex, [Ru(C10H8N2)2(C5H6N2)2](PF6)2·CH3CN, the RuII atom is bonded to two α-diimine ligands, viz. 2,2′-bipyridine, in a cis configuration and to two 4-aminopyridine (4Apy) ligands in the expected distorted octahedral configuration. The compound is isostructural with [Ru(C10H8N2)2(C5H6N2)2](ClO4)2·CH3CN [Duan et al. (1999 ▶). J. Coord. Chem. 46, 301–312] and both structures are stabilized by classical hydrogen bonds between 4Apy ligands as donors and counter-ions and acetonitrile solvent molecules as acceptors. Indeed, N—H⋯F interactions give rise to an intermolecularly locked assembly of two centrosymmetric complex molecules and two PF6 − counter-ions, which can be considered as the building units of both crystal architectures. The building blocks are connected to one another through hydrogen bonds between 4Apy and the connecting pieces made up of two centrosymmetric motifs with PF6 − ions and acetonitrile molecules, giving rise to ribbons running parallel to [011]. 21-Screw-axis-related complex molecules and PF6 − counter-ions alternate in helical chains formed along the a axis by means of these contacts.