Ricardo Ugarte

SYNTHESIS AND CONFORMATIONAL ANALYSIS OF LEPTOCARPIN DERIVATIVES: INFLUENCE OF MODIFICATION OF THE OXIRANE RINGON LEPTOCARPIN'S CYTOTOXIC ACTIVITY

The reaction in acidconditions of Leptocarpin 1, a compound with antitumor activity, formed two new isomeric products, 8b-angeloyl-1b,3b-dihydroxy-4,10-dimethyl,-D11(13) methylen-4Z,9Z-dieneheliangol-6,12-olide 2 and 8b-angeloyl-1b,3b-dihydroxy-4-methyl-D11(13),D11(14)-dimethylen-4Z-eneheliangol-6,12-olide 3, whose structures reported in this study were established by spectroscopy (1H-NMR, 13C-NMR, MS and IR) and confirmedthrough ROESY experiments and theoretical studies by molecular mechanics. The in vitro cytotoxicity of these isomeric compounds was less active than leptocarpin, showing the importance of the oxirane ring in the biological activity. Cytotoxic activity was measured in six cancer cell lines

Reactivity of [Mo(NHNRPh)(NNRPh)(acac)X2] (R=Ph, Me; X=Br, I) toward tertiary phosphines

The reactivity of mixed [organohydrazido(1-)][organohydrazido(2-)]molybdenum(VI) complexes [Mo(NHNRPh)(NNRPh)(acac)X2] {R = Ph, X = Br (1); R = Ph, X = I (2) and R = Me; X = I (3)} with tertiary phosphines as PPh3, PMePh2 and PMe2Ph are examined. The syntheses of [Mo(NNPh2)2Br2(PPh3)] (4), [Mo(NNPh2)2Br2(PMePh2)2] (5), [Mo(NNPh2)2Br2(PMe2Ph)2] (6), [Mo(NNPh2)2(acac)I(PPh3)] (7), [Mo(NNPh2)2(acac)(PMePh2)2]+I− (8) and [Mo(NNMePh)2(acac)(PMePh2)2]+I− (9) are reported. All complexes were characterized by elemental analysis, UV-visible, IR, 1H and 31P{H} NMR spectroscopy.

Quimioluminiscencia electrogenerada del luminol usando electrodos de bajo costo

The purpose of the study was to observe eletrogenerated chemiluminescence (ECL) of luminol using different materials as electrodes such as wires, nails, coins, razor blades, etc. Based on the experimental observations and the mechanisms proposed in the literature, students should be capable of analyzing their results in order to understand the phenomena studied. Students could then elaborate a mechanism of action consistent with the experimental results which could rationalize the formation of intermediates in the reaction and the dependence of ECL on solution pH in addition to other points of interest

THEORETICAL STUDY OF THE ISOMERIZATION OF MALEIC ACID INTO FUMARIC ACID

ABSTRACT The isomerization reaction of 2-butenedioic acid in gas phase has been studied using Hartree-Fock (HF), Moller-Plesset to 2 nd order (MP2) and BLYP, B3LYP Density Functional Theory (DFT) levels of approximation. Potential energy surfaces (PES) of the singlet and triplet states of the molecule are constructed in order to corroborate the hypothesis that the reaction proceeds by a non-adiabatic path. A total of ten stationary points (eight singlet and two triplet) were characterized as energy minima or saddle points. Thermochemical analysis of the triplet conformers and singlet most stable structures yields a value of the ΔH° of activation for isomerization that is in good agreement with the expected results. Keywords: Potential energy surface; Isomerization Maleic acid; DFT calculations. e-mail address: rugarte@uach.cl 1. INTRODUCTION As is well known, substituted ethylenes exhibit cis-trans isomerism. For instance maleic acid transforms into fumaric acid at high temperatures (melting point); this transformation is often accompanied by partial descomposition. The isomerization also occurs by heating an aqueous solution of maleic acid in a sealed tube above 130° C, by catalyzing with various acids and salts at ≈ 100° C and as a result of bromine atoms.

Estudio teórico de la isomerización del ácido maleico en ácido fumárico: un enfoque basado en el concepto de superficie de energía potencial

A comparative study based on potential energy surfaces (PES) of 2-butanedioic and hypothetic 2-butanedioic/HCl acids is useful for understanding the maleic acid isomerization. The PES enables locating conformers of minimum energy, intermediates of reactions and transition states. From contour diagrams, a set of possible reaction paths are depicted interconnecting the proposed structures. The study was carried out in absentia and in the presence of the catalyst (HCl), using an solvatation model provided by the Gaussian software package. Clearly, the effect of HCl is given by new reaction paths with lower energetic barriers in relation to the reaction without catalyzing.

Reactivity of organohydrazidomolybdenum(VI) complexes toward tertiary phosphines

The reactivity of mixed [organohydrazido(1-)][organohydrazido(2-)]molybdenum(VI) complexes [Mo(NHNRPh)(NNRPh)(acac)X2] {R = Ph, X = Br (1); R = Ph, X = I (2) and R = Me; X = I (3)} with the tertiary phosphines PPh3, [PMePh2 and PMe2Ph has been investigated. The syntheses of [Mo(NNPh2)2Br2(PPh3)] (4), [Mo(NNPh2)2Br2(PMePh2)2] (5), [Mo(NNPh2)2Br2(PMe2Ph)2] (6), [Mo(NNPh2)2(acac)I(PPh3)] (7), [Mo(NNPh2)2(acac)(PMePh2)2]+I− (8) and [Mo(NNMePh)2(acac)(PMePh2)2]+I− (9) are reported. Complexes were characterized by analysis, and electronic, IR, 1H and 31P{H} NMR spectroscopy.