Structural Analysis of Ti And Pb Citrate Using NMR and FT-Raman Signals and Quantum Mechanics Simulations

Titanium citrate and lead and titanium citrate were prepared by polymeric precursor method in aqueous solution. This citrate was analyzed by ¹H, ¹³C NMR and gHMBC–NMR (Hetero-nuclear multiple-bond correlation) to investigate the formation of the citrate complexs and influence of the Pb²⁺ ion in this complex. These complexs were characterized by interaction between Ti⁴⁺ ion and citric acid carboxyls. Quantum mechanic simulations in level ab initio were used to study the electronic structure and natural charges (NBO) to both the complexs. Such techniques indicated the formation of an octahedral complex with an arrangement similar to Ti atom in the crystalline structure of the PbTiO₃. A study using the technique FT-Raman made possible the confirmation of the interaction among the Ti⁴⁺ and Pb²⁺ ions with the citric acid carboxyls.     

Fluorimetric determination of aflatoxins by flow-injection analysis

Summary A fast and inexpensive fluorimetric method for the determination of total aflatoxins (B₁, B₂, G₁, and G₂) in food of use in screening numerous samples suspectedly containing these substances is proposed. The sensitivity of the method (determination range between 0.5 and 200.0 ng ml^–1) allows these analytes to be detected at concentrations well below legal limits; hence, separation-detection techniques such as HPLC need only be used with samples in which these compounds are found to occur. The method has been applied to maize, peanut and tapioca samples, obtaining average recoveries of 100.9 with deviations of ±5% with respect to 100% recovery.

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Fluorometrische Bestimmung von Aflatoxinen durch Fließinjektionsanalyse

     

Photochimie d''heterocycles azotes—VI : Synthese par voie photochimique d''amino et d''alkoxy indazoles

The preparation of different aminoindazoles by nucleophilic aromatic photosubstitution of nitroindazoles by amines is described. In this manner, the amino, methylamino, dimethylamino and dimethylamino substituents are introduced in 3,4,5 or 7-position. The irradiation in the presence of ethanol gives ethoxyindazoles in only four cases. Two demethylation reactions have been observed: the first one concerns the formation of methylamino derivatives starting from dimethylamine; the second one, the formation of N(H)1-indazoles by irradiation in presence of diethylamine.     

Synthesis of Phosphohomoserine Lactone,A New Pseudopeptide Unit

We describe here the synthesis of the enantiomerically pure phosphohomoserine lactone which will serve as an haptenic structure in catalytic antibody preparation.     

p-sd Shell gap reduction in neutron-rich systems and cross-shell excitations in 20 O

Excited states in 20O were populated in the reaction 10Be(14C,alpha) at Florida State University (FSU). Charged particles were detected with a particle telescope consisting of 4 annularly segmented Si surface barrier detectors and gamma radiation was detected with the FSU gamma detector array. Five new states were observed below 6 MeV from the alpha-gamma and alpha-gamma-gamma coincidence data. Shell model calculations suggest that most of the newly observed states are core-excited 1p-1h excitations across the N=Z=8 shell gap. Comparisons between experimental data and calculations for the neutron-rich O and F isotopes imply a steady reduction of the p-sd shell gap as neutrons are added.     

Measurement of Total and Unbound Mycophenolic Acid and Its Glucuronide by LC Coupled with MS. Application to a Pharmacokinetic Study of Mycophenolate Mofetil in Patients with Autoimmune Diseases

Liquid chromatography coupled with mass spectrometry for the determination of total and unbound mycophenolic acid and its major metabolite in human plasma has been developed. Sample preparations were based on a fully automated solid-phase extraction process and ultrafiltration. Mass spectrometric data were acquired in a single-ion monitoring method. The analytes and nevirapine (internal standard) were well separated in an isocratic mode over 8 min. Validation study exhibited excellent linearity, with intra- and inter-day precision and accuracy of less than 12%. The assay was successfully applied to the pharmacokinetic study of mycophenolic acid in patients with autoimmune diseases.     

Microwave-assisted organocatalytic enantioselective intramolecular aza-Michael reaction with α,β-unsaturated ketones

An organocatalytic enantioselective intramolecular aza-Michael reaction of carbamates bearing conjugated ketones as Michael acceptors is described. By using 9-amino-9-deoxy-epi-hydroquinine as the catalyst and pentafluoropropionic acid as a co-catalyst, a series of piperidines, pyrrolidines, and the corresponding benzo-fused derivatives (indolines, isoindolines, tetrahydroquinolines, and tetrahydroisoquinolines) can be obtained in excellent yields and enantioselectivities. In addition, the use of microwave irradiation at 60 °C improves the efficiency of the process giving rise to the final products with comparable yields and enantiomeric excesses. Some mechanistic insights are also considered.     

Protonation and deprotonation of hydroxamic acids. An MO ab initio study

Ab initio molecular orbital calculations with 4-31G//4-31G, 6-31G^*//4-31G and 6-31+G//4-31G basis sets have been used to examine the structure, relative energy, protonation and deprotonation of a series of seven hydroxamic acids in the gas phase. The results show that hydroxamic acids are predominantly in the E-TS form and that the most probable protonation site is the carbonyl oxygen atom, while deprotonation proceeds by loss of NH hydrogen.     

Synthèse et réactivité de nitro indazoles

Synthese and nmr study of forty-four nitroindazoles in which twentry-three were never published have been carried out. The best way to obtain the halogenomethyl derivatives(halogenation before or after methylation) is shown. Relative reactivities of the different heterocyclic ring positions toward the electrophilic agent are discussed.