Amberlite IR-120: A reusable catalyst for N-formylation of amines with formic acid using microwaves

A rapid and practical green route for the N-formylation of amines with formic acid using Amberlite IR-120 as a catalyst is described. This method provides an efficient and much improved modification over the reported methods in terms of yield, reaction time, and work-up procedure. A wide variety of substituents is tolerated, which is not the case for existing procedures

Studies on the crystallization and melting behavior of poly(ethylene2,6-naphthalate)

Crystallization behaviour of low molecular weight (oligomeric) and high molecular weight poly(ethylene 2,6-naphthalate)s (PEN) was studied using wide angle X-ray diffraction (WAXS) and differential scanning calorimetry (DSC). It was found that the crystallization conditions determine the nature of crystalline modification. Crystallization from the glassy state gives a-modification, whereas, crystallizing from the melt above 220°C results in β-modification. In contrast, the oligomers gives both the modifications up on crystallizing from the melt. The equilibrium melting temperatures of PEN were determined from DSC experiments, based on conditions of crystallization of a and β-modifications

Combustion derived nanocrystalline-ZrO2 and its catalytic activity for Biginelli condensation under microwave irradiation

Nanocrystalline zirconium(IV) oxide (nc-ZrO2) possessing high surface area was synthesized by a low temperature eco-friendly solution combustion method using a new organic fuel alanine. The powder XRD, SEM and surface area measurements were carried out for characterization of nc-ZrO 2. The powder XRD results revealed that, the nc-ZrO2 has the pure tetragonal phase. The crystallite size calculated by Scherrer's formula and BET surface area were found to be ca. 53-57 nm and ca. 275 m2/g, respectively. SEM micrograph exhibited the macroporous nature of the powder. nc-ZrO2 has been employed as a catalyst for the solvent-free synthesis of 3,4-dihydro- pyrimidin-2-ones (DHPMs) by a microwave (MW) assisted one-pot, multicomponent Biginelli condensation reaction of araldehydes, ethylacetoacetate and urea or thiourea. DHPMs are obtained in good to excellent yields (85-96) under this reaction condition within short interval of time (10-20 min). Nanocrystalline zirconium(IV) oxide (nc- ZrO2) possessing high surface area was synthesized by a low temperature eco-friendly solution combustion method using a new organic fuel alanine. The powder XRD, SEM and surface area measurements were carried out for characterization of nc-ZrO2. Copyright © 2011 SIOC, CAS, Shanghai & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Structural characterization of folded and extended conformations in peptides containing gamma amino acids with proteinogenic side chains: crystal structures of gamma(n), (alpha gamma)(n) and gamma gamma delta gamma sequences

The crystal structures of nine peptides containing gamma(4)Val and gamma(4)Leu are described. The short sequences Boc-gamma(4)(R)Val](2)-OMe 1, Boc-gamma(4)(R)Val](3)-NHMe 2 and Boc-gamma(4)(S)Val-gamma(4)(R)Val-OMe 3 adopt extended apolar, sheet like structures. The tetrapeptide Boc-gamma(4)(R)Val](4)-OMe 4 adopts an extended conformation, in contrast to the folded C-14 helical structure determined previously for Boc-gamma(4)(R)Leu](4)-OMe. The hybrid alpha gamma sequence Boc-Ala-gamma(4)(R)Leu](2)-OMe 5 adopts an S-shaped structure devoid of intramolecular hydrogen bonds, with both alpha residues adopting local helical conformations. In sharp contrast, the tetrapeptides Boc-Aib-gamma(4)(S)Leu](2)-OMe 6 and Boc-Leu-gamma(4)(R)Leu](2)-OMe 7 adopt folded structures stabilized by two successive C-12 hydrogen bonds. gamma(4)Val residues have also been incorporated into the strand segments of a crystalline octapeptide, Boc-Leu-gamma(4)(R)Val-Val-(D)Pro-Gly-Leu-gamma(4)(R)Val-Val-OMe 8. The gamma gamma delta gamma tetrapeptide containing gamma(4)Val and delta(5)Leu residues adopts an extended sheet like structure. The hydrogen bonding pattern at gamma residues corresponds to an apolar sheet, while a polar sheet is observed at the lone delta residue. The transition between folded and extended structures at gamma residues involves a change of the torsion angle from the gauche to the trans conformation about the C-beta-C-alpha bond

Synthesis, biological evaluation, and computational investigation of ethyl 2,4,6-trisubstituted-1,4-dihydropyrimidine-5-carboxylates as potential larvicidal agents against Anopheles arabiensis

Malaria is one of the most known vector-borne diseases caused by female Anopheles mosquito bites. According to WHO, about 247 million cases of malaria and 619,000 deaths were estimated worldwide in 2021, of which 95% of the cases and 96% of deaths occurred in the African region. Sadly, about 80% of all malaria deaths were of children under five years old. Despite the availability of different insecticides used to control this disease, the emergence of drug-resistant mosquitoes threatens public health. This, in turn, highlighted the need for new larvicidal agents that are effective at different larval life stages. This study aimed to identify novel larvicidal agents. To this end, a series of ethyl 2,4,6-trisubstituted-1,4-dihydropyrimidine-5-carboxylates 8a-i was synthesized using a three-step chemical synthetic approach via a Biginelli reaction employed as a key step. All title compounds were screened against Anopheles arabiensis to determine their larvicidal activities. Among them, two derivatives, ethyl 2-((4-bromophenyl)amino)-4-(4-fluorophenyl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate 8b and ethyl 2-((4-bromo-2-cyanophenyl)amino)-4-(4-fluorophenyl)-6-methyl-1,4-dihydropyrimidine-5-carboxylate 8f, showed the highest larvicidal activity, with mortality of 94% and 91%, respectively, and emerged as potential larvicidal agents. In addition, computational studies, including molecular docking and molecular dynamics simulations, were carried out to investigate their mechanism of action. The computational results showed that acetylcholinesterase appears to be a plausible molecular target for their larvicidal property.Fil: Duraisamy, Ramasamy. Thiruvalluvar University; IndiaFil: Al-Shari, Nizar A.. Jordan University Of Science And Technology; JordaniaFil: Chandrashekharappa, Sandeep. National Institute Of Pharmaceutical Education And Rese; IndiaFil: Deb, Pran Kishore. Philadelphia University Jordan; JordaniaFil: Gleiser, Raquel M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinar de Biología Vegetal (P). Grupo Vinculado Centro de Relevamiento y Evaluación de Recursos Agrícolas y Naturales; ArgentinaFil: Tratrat, Christophe. King Faisal University; Arabia SauditaFil: Chopra, Deepak. Indian Institute Of Science Education And Research Bhopal; IndiaFil: Muthukurpalya Bhojegowd, Madhusudana Reddy. Reva University; IndiaFil: Thirumalai, Dhakshanamurthy. Thiruvalluvar University; IndiaFil: Morsy, Mohamed A.. King Faisal University; Arabia SauditaFil: Ibrahim, Yasmine F.. King Faisal University; Arabia SauditaFil: Mohanlall, Viresh. Durban University Of Technology; SudáfricaFil: Venugopala, Katharigatta N.. Durban University Of Technology; Sudáfric