Gustavo Metzker

Photodegradation of folate sensitized by riboflavin.

Folate is shown to react with singlet‐excited state of riboflavin in a diffusion controlled reaction and with triplet‐excited state of riboflavin in a somewhat slower reaction with 3kq = 4.8 × 108 L mol−1 s−1 in aqueous phosphate buffer at pH 7.4, ionic strength of 0.2 mol L−1, and 25°C. Singlet quenching is assigned as photo‐induced reductive electron transfer from ground state folate to singlet‐excited riboflavin, while triplet quenching is assigned as one‐electron transfer rather than hydrogen atom transfer from folate to triplet‐excited riboflavin, as the reaction quantum yield, φ = 0.32, is hardly influenced by solvent change from water to deuterium oxide, φ = 0.37. Cyclic voltammetry showed an irreversible two‐electron anodic process for folate, E = 1.14 V versus NHE at a scan‐rate of 50 mV s−1, which appears to be kinetically controlled by the heterogeneous electron transfer from the substrates to the electrode. Main products of folate photooxidation sensitized by riboflavin were pterin‐6‐carboxylic acid and p‐aminobenzoyl‐l‐glutamic acid as shown by liquid chromatographic ion‐trap mass spectrometry (LC‐IT‐MS).

Nitric oxide as an activation agent for nucleophilic attack in trans-[Ru(NO)(NH3)4{P(OEt)3}](PF6)3

P{ 1 H} NMR), espectroscopia no infravermelho (FTIR), ressonância paramagnetica eletronica (EPR), voltametria ciclica (CV), espectroscopia eletronica (UV-Vis) e analise elementar. De acordo com os dados experimentais e calculos de mecânica quântica (DFT), a reacao ocorre no estado solido pelo ataque nucleofilico no ester de fosforo coordenado devido a forte polarizacao no eixo P

α,α-Alkylation-Halogenation and Dihalogenation of Sulfoxonium Ylides. A Direct Preparation of Geminal Difunctionalized Ketones

A one-pot alkylation-halogenation of ketosulfoxonium ylides in the presence of alkyl halides is described. The method furnishes several gem-difunctionalized haloketones (an alkyl and F, Cl, Br, or I) in good yields. Replacing alkyl halides with a mixture of electrophilic halogen species and various halide anions led to gem-dihalogenated ketones containing a combination of the same or two different halogens. Kinetic isotopic effects as well as reaction kinetic experiments give insight to the mechanism of these reactions.