Evaluation of the Use of Elicitors for the Production of Antioxidant Compounds in Liquid Cultures of Ganoderma curtisii from Costa Rica

The use of substances or conditions as elicitors can significantly increase the production of secondary metabolites. In this research, the effects of different elicitors on the production of antioxidant secondary metabolites were evaluated in a strain of Ganoderma sp. The elicitors tested were pH changes in different growth phases of the fungus (pH 3, 5.5 and 8), different concentrations of peptone as a nitrogen source (1 g/L and 10 g/L), and the addition of chemical agents to the culture medium (ethanol, growth regulators, and salts). The alkaline pH during the stationary phase and the high availability of nitrogen were effective elicitors, producing cultures with higher antioxidant activity (37.87 g/L and 43.13 g/L dry biomass) although there were no significant differences with other treatments.     

Spectrophotometric Determination of Piperazine,Piperazine Salts and Diethylcarbamazine Citrate with Chloranilic Acid

Abstract

A rapid and sensitive spectrophotometric method is developed for the quantitative determination of piperazine, piperazine salts and diethylcarbamazine citrate. The method is based on the formation of donor-acceptor complexes between the compound and chloranilic acid. The interaction product has a characteristic absorption maximum at about 345 nm. The system obeys Beer's law in the concentration range of 1–10 ugml^?1 of piperazine hexahydrate, adipate, phosphate, citrate and diethylcarbamazine citrate. The effects of several experimantal variables have been studied and the stoichiometric composition of the complex has been determined. The developed procedure has been found to be simple, rapid and precise and its application to various dosage forms was demonstrated and yields results comparable with the standard method.     

Synthesis and characterization of 1-phenyl-3-alkylbenzimidazol-2-ylidene salts and their catalytic activities in the Heck and Suzuki cross-coupling reactions

The synthesis and characterization of 1-phenyl-3-alkyl-substituted carbene precursors that were prepared from 1-phenyl substituted benzimidazole and various alkyl halides are reported. The new benzimidazolium salts (1a–e) were characterized by ¹H NMR, ¹³C NMR, FT-IR spectroscopic methods and elemental analyses. New in situ generated palladium-benzimidazolium complexes were tested for catalytic activity in the Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions.     

A Synthetic Strategy for Novel Organothiophosphates Incorporating a Pyridine Ring

Eight novel amidothiophosphates have been successfully achieved using cycloiminium salts of pyridine as the starting material. Phosphorylation was done using phosphorus trichloride, and the resulting functionalized iminohalophosphines in situ were further oxidized and substituted through sulfur and a suitable secondary amine (alkyl, alicyclic, and aryl). The reactions were carried out in a dry nitrogen atmosphere. The synthesized products were characterized using different spectroscopic techniques (¹H and ³¹P NMR). The pyridine nucleus incorporating a phosphoryl group is highly bioactive. Hence, the synthesized organothiophosphates should be potential pesticidal molecules.     

Kinetics of Alkaline Hydrolysis of Quaternary Phosphonium Salts. The Influence of Protic and Aprotic Solvents on the Hydrolysis of Alkyl Phenylphosphonium Salts

Abstract

Third order rate constants have been determined for the alkaline hydrolysis of four series of alkylphenylphosphonium salts and alkylphenylbenzylphosphonium salts at various temperatures in 50%–70% ^v/_v aqueous tetrahydrofuran and 70% ^v/_v aqueous methanol. Thermodynamic activation parameters have been calculated for the reactions of each substrate and the effects of varying the ratio of alkyl to phenyl groups have been compared, as well as the effects of changes in the nature of the alkyl group. Solvation, as revealed by trends in entropy of activation, plays a largely counter-balancing role with respect to enthalpy and energy of activation. The role of the isokinetic effect is discussed. In aqueous tetrahydrofuran, solvation effects on the hydrolyses of phosphonium salts change as the mole fraction of water changes, and for aqueous methanol the trends in the thermodynamic activation parameters actually reverse.     

STEREOSELECTIVE VINYLATION OF METHYL-2-HYDROXY-3-NAPHTHOATE MEDIATED BY VINYL TRIPHENYLPHOSPHONIUM SALTS

Protonation of the highly reactive intermediate produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylate 1a–c by methyl-2-hydroxy-3-naphthoate lead to vinyl triphenylphosphonium salts which undergo aromatic electrophilic substitution reaction with phenolate-conjugated base to produce 2a–c.     

Synthesis and Stereochemistry of Optically Active Selenium and Tellurium Compounds

Abstract

The synthesis and stereochemistry of tricoordinated optically active selenium and tellurium compounds are described. Telluronium salts, telluronium imides, and seleninic acids were prepared and optically resolved by fractional recrystallization of diastereomeric mixtures or by chromatography using a chiral column of racemic mixtures. Diphenyl dichalcogenides also were optically resolved by chiral crystallization. Their absolute configurations were determined or estimated based on X-ray crystallographic analysis, specific rotations, and circular dichroism spectra. The kinetic studies and the mechanism for the racemization were also studied.