Noe Rosas

Perspectives of antimony compounds in oncology

AbstractAntimony, a natural element that has been used as a drug for over more than 100 years, has remarkable therapeutic efficacy in patients with acute promyelocytic leukemia. This review focuses on recent advances in developing antimony anticancer agents with an emphasis on antimony coordination complexes, Sb (III) and Sb (V). These complexes, which include many organometallic complexes, may provide a broader spectrum of antitumoral activity. They were compared with classical platinum anticancer drugs. The review covers the literature data published up to 2007. A number of antimonials with different antitumoral activities are known and have diverse applications, even though little research has been done on their possibilities. It might be feasible to develop more specific and effective inhibitors for phosphatase-targeted, anticancer therapeutics through the screening of sodium stibogluconate (SSG) and potassium antimonyltartrate-related compounds, which are comprised of antimony conjugated to different organic moieties. For example, SSG appears to be a better inhibitor than suramin which is a compound known for its antineoplastic activity against several types of cancers.

Tertiary stibines containing aromatic heterocycles and their silver complexes: synthesis and X-ray structures

Abstract The work presents the synthesis of tertiary stibines containing heterocyclic aromatic groups of general formula (2-C4H3X)3Sb where X=S (1), O (2) or NMe (3). These stibines were brominated to give corresponding dibromide and were complexed with silver(I) nitrate. The stibines, dibromides and their silver complexes were characterized by elemental analyses, IR, UV, mass, 1H, 13C, COSY, HETCOR NMR spectroscopy. Molecular structures of (2-C4H3S)3Sb (1); (2-C4H3S)3SbBr2 (4) and {Ag[(2-C4H3S)3Sb]2}NO3 (6) were determined by X-ray spectroscopy. This is the first X-ray crystallographic report on stibines containing heterocyclic aromatic groups and their silver complexes. The stibine (1) is pyramidal while its dibromide has trigonal bipyramidal structure. The silver complex (6) has a polymeric nature with NO3− acting as a bridging ligand.

Catalytic hydrocyanation of α-ketoalkynes by Ni(CN)2/CO/KCN system in alkaline aqueous media: Identification of the active species

Abstract 5-Hydroxy-3-pyrrolin-2-ones are regioselectively synthesized in a good yield under very mild conditions by tetracyanonickelate (0) ion catalyzed hydrocyanation of α-ketoalkynes, in the absence of hydrogen cyanide. The catalyst is prepared in situ in a basic aqueous medium by reduction of Ni(CN) 2 with CO in the excess of KCN. From the IR spectroscopy studies and by evaluation of catalytic activity of some cyanonickelates it is proposed that [Ni(CN) 4 ] −4 anion is the active species in the process. A possible mechanism is suggested for the conversion of nickel cyanide to [Ni(CN) 4 ] −4 . The effect of the reaction variables, e.g.: reaction time, temperature, absorption of carbon monoxide, the concentration of potassium cyanide, water, substrate, and sodium hydroxide were also examined.

Catalytic auto-condensation of 2,4-pentanedione promoted by Sm(III) acetylacetonate: the X-ray structure of a novel complex [Sm(CH3COO)3(H2O)2](H2O)2

Abstract An efficient one-pot catalytic method to obtain 4,6-dimethyl-2-hydroxyacetophenone (A) is reported, the reaction proceeds via the intermolecular auto-condensation of 2,4-pentanedione using samarium(III) acetylacetonate (Sm(AcAc)3) as promoter. A novel complex [Sm(CH3COO)3(H2O)2](H2O)2 (I) was isolated from the reaction media. The structure of I was determined by X-ray crystallography showing that the central atom is ennea-coordinated (monocapped square-antiprism geometry). This complex I also shows activity in the named autocondensation reaction.

Hydroformylation versus hydrocarboxylation of cyclohexene under homogeneous WGSR conditions: The study of Co2(CO)8 diphos/THF-H2O system

Abstract The catalytic system Co 2 (CO) 8 /diphos/THF-H 2 O, an effective catalyst for carbonylation reactions, was studied for simultaneous hydrocarboxylation and hydroformylation of cyclohexene. Using this catalytic system, cyclohexene with CO and H 2 O gives cyclohexenecarboxaldehyde and cyclohexenecarboxylic acid as the main reaction products and cyclohexylmethanol as by-product. The catalytic reaction shows that the hydrocarboxylation/hydroformylation ratio is dependent on water concentration and the reaction temperature. The effects of the other reaction variables such as CO pressure and catalyst concentration were also examined.

Characterization of a novel [Sm(HMPA)4I2]I complex by positive ion fast atom bombardment and high resolution mass spectrometry

Abstract A positive-ion Fast Atom Bombardment (FAB) study was performed to determine the structure of samarium(III) triiodine complex (I). Collision Induced Dissociation (CID) and High Resolution Mass Spectrometry were used to establish the fragmentation pattern of the C24H72O4N12P4I3Sm compound. The structure of (I) was confirmed by X-ray analysis.

The crystal structure of a novel complex [Sm(HMPA)3(H20)4]3+3[I−] formed in the reductive cyclodimerization of linear α,β-unsaturated ketones by SmI2

Abstract The samarium iodide/HMPA has been used to promote cyclodimerization of linear α,β-unsaturated ketones. A novel complex [Sm(HMPA) 3 (H 2 O) 4 ] 3+ 3[I − ] ( 1 ) was isolated from the reaction and its X-ray crystal structure was determined. The Sm ion is hepta-coordinated displaying a pentagonal bipyramid geometry and an extensive hydrogen-bond network which keeps together the molecules in the crystal.

One Pot Syntheses of Substituted Naphthyridines and 2H-Pyrano[3,2-g]-quinolin-2-ones in Water

One pot catalytic syntheses of substituted 1,8-naphthyridines and 2H-pyrano[3,2-g]quinolin-2-ones by the reaction of α-ketoalkynes with 6-aminonicotinamide and 7-amino-4-methylcoumarin respectively in water, using a homogeneous nickel catalyst at very mild reaction conditions are described. In the absence of this catalytic system very low yields are obtained even after long reaction time.

Allylic Versus Vinlic Oxidation of Cyclohexene Promoted by Transition Metal β-Diketonates

Abstract We report the cyclohexene oxidation by molecular oxygen in the presence of several metal β-diketonates. The catalytic conditions used showed an allylic/vinylic oxidation (ao/vo) ratio equal to 1.5. The complexes M(L)n were used with the metal ions Co(III), Ni(II), Pd(II), Cu(II), chelated with acetylacetone (AcAc), benzoylacetone (BeAc) and dibenzoylacetone (BeBe) as ligands. The oxidation selectivity of the studied system suggests a different allylic/vinylic pathway compared with that observed in previous reports.

Novel rhodium–antimony bimetallic complexes containing an unusual distibine cis-eclipsed conformation

Rhodium–antimony bimetallic complexes, which represent rare examples of an unusual cis-eclipsed conformation of the phenyl groups in the ligating distibine, are synthesised and characterised by IR, mass spectrometry and X-ray crystallography.