Sulfamic Acid–Catalyzed,Three-Component,One-Pot Synthesis of [1,2,4]Triazolo/Benzimidazolo Quinazolinone Derivatives

An efficient and convenient approach is reported for three-component, one-pot synthesis of the [1,2,4]triazolo/benzimidazolo quinazolinones by condensation of 2-amino benzimidazole or 3-amino-1,2,4-triazole as amine sources with dimedone and different aldehydes in the presence of sulfamic acid as a reusable, green catalyst in acetonitrile and under heating conditions.     

EFFICIENT AND SELECTIVE OXIDATION OF THIOLS TO DISULFIDES BY 1,4-DIAZABICYCLO[2.2.2]OCTANE-DI-N-OXIDE-DI-PERHYDRATE UNDER NEUTRAL AND HETEROGENEOUS CONDITIONS

1,4-Diazabicyclo[2.2.2]octane-di-N-oxide-di-perhydrate[3pc] selectively oxidizes thiols to disulfides in acetonitrile in good yields. The method is generally useful for a wide variety of thiols.     

Synthesis of New 1,4-Dihydropyridine Derivatives Containing Thiazolyl Substituents

A series of 4-[2-methyl (or aryl) thiazole-4-yl]-2,6-dimethyl-3,5-diacetyl (or dibenzoyl) 1,4-dihydropyridines were synthesized using a modified Hantzsch reaction involving the condensation of the corresponding aldehyde with acetyl acetone or benzoyl acetone. The preparation of the corresponding aldehydes (2-methylthiazole-4-carboxaldehyde and some 2-arylthiazole-4-carboxaldehydes) was achieved by a simplified protocol of the published synthesis.     

Host-guest inclusion complex between β-cyclodextrin and paeonol: A theoretical approach

Host-guest interactions of β-cyclodextrin (β-CD) with paeonol (PAE) were simulated using semi-empirical PM3 and both ONIOM2 [(B3LYP/6-31G*:PM3), (HF/6-31G*:PM3)] methods. The results obtained with PM3 method clearly indicate that the complexes formed are energetically favored with or without solvent, the model 1 (PAE entering into the cavity of β-CD from its wide side by OCH3 group) is found more favored than the model 2 (PAE entering into the cavity of β-CD from its wide side by COCH3 group). Finally, natural bonding orbital (NBO) analysis was performed based on ONIOM2 optimized complexes to quantify the donor–acceptor interactions between PAE and β-CD.     

A one-pot synthesis of 5,5-disubstituted hydantoin derivatives using magnetic Fe3O4 nanoparticles as a reusable heterogeneous catalyst

A facile and rapid method for the one-pot synthesis of 5,5-disubstituted hydantoins in the presence of magnetic Fe₃O₄ nanoparticles has been developed. The multicomponent reactions of carbonyl compounds (aldehydes and ketones), potassium cyanide and ammonium carbonate were carried out under solvent-free conditions to obtain various hydantoin derivatives. The magnetic catalyst could be readily separated by an external magnet from the reaction mixture. This procedure has many advantages, such as the use of a reusable magnetic catalyst, high yields, short reaction times, simplicity and very easiness with implementing the methodology.     

Multispectroscopic Studies on the Interaction of a Platinum(II) Complex Containing l-Histidine and 1,10-Phenanthroline Ligands with Bovine Serum Albumin

The mechanism of the interaction between bovine serum albumin (BSA) and [Pt(phen) (histidine)]⁺ complex was studied employing ultraviolet (UV) absorption, circular dichroism (CD), FT-IR, differential pulse voltammetry (DPV), and fluorescence spectral methods. Fluorescence data showed that the intrinsic fluorescence of BSA was strongly quenched by Pt(II) complex in terms of an untypical static quenching process. The corresponding number of binding sites (n) and binding constant (K _b) of BSA and complex at 283, 298, and 310 K were calculated to be 0.61?×?10⁶, 19?×?10⁶, and 42?×?10⁶ M^?1, respectively. The results showed that the increasing temperature improves the stability of the complex–BSA system, which results in a higher binding constant and the number of binding sites of the complex–BSA system. The positive ΔH and positive ΔS indicated that hydrophobic forces might play a major role in the binding between complex and BSA. Based on Forster’s theory of non-radiation energy transfer, the binding distance (r) between the donor (BSA) and acceptor (Pt(II) complex) was evaluated. The results of CD, UV–vis, DPV, and FT-IR spectroscopy showed that the binding of Pt(II) complex to BSA induced conformational changes in BSA     

Modification of Lysine Residues of Horseradish Peroxidase and Its Effect on Stability and Structure of the Enzyme

Biotechnology is consistently seeking improved enzyme stability. Enzymes have great properties, although their marginal stability limits their applications. Among the strategies for improving stability of the enzymes, chemical modification is a simple and effective technique. In the present study, chemical modification of horseradish peroxidase (HRP) was carried out with 2,3-dichloromaleic anhydride and 2,3-dimethylmaleic anhydride. HRP is an important heme-containing enzyme. It is widely applied in pharmacological, chemical, and medical industries. Here, thermal stability of HRP was investigated at different temperatures. In addition, the enzyme stability was evaluated in urea, DMSO, alkaline pH, and hydrogen peroxide solutions by spectroscopic techniques. Structural investigation indicated that the both anhydrides slightly decrease compactness of the enzyme structure. The results also indicated that 2,3-dichloromaleic anhydride increases thermal stability of the enzyme and its stability in urea and DMSO solutions, but 2,3-dimethylmaleic anhydride only stabilizes HRP in urea solution. Furthermore, the experiments implied that none of the modifiers are effective on the stability of HRP in extreme pH and oxidative condition. Catalytic efficiency and activation energy did not change remarkably following reaction of the enzyme with the both carboxylic anhydrides. Consequently, improvement in the stability of HRP depends on not only the type of modifier but also denaturing condition.