Phenacylsulfonylacetic acid methyl ester‐synthon for 1,2,3‐selena/thiadiazoles and 2H‐diazaphospholes

A new class of 1,2,3‐selena/thiadiazoles and 2H‐diazaphospholes were synthesized by exploiting α‐ketomethylene group in phenacylsulfonylacetic acid methyl ester.     

Rigid dipeptide mimics: synthesis of enantiopure C6-functionalized pyrrolizidinone amino acids

Enantiopure (3S,5S,6R,8S)- and (3S,5S,6S,8S)-6-hydroxypyrrolizidinone 3-N-(Boc)amino 8-methyl carboxylates (6R)- and (6S)-1 were synthesized in seven steps starting from (2S)-alpha-tert-butyl N-(PhF) aspartate beta-aldehyde (10). Carbene-catalyzed acyloin condensation of beta-aldehyde 10 followed by acetylation provided a separable mixture of diastereomeric (2S,5RS,7S)-diamino-4-oxo-5-acetoxysuberates (13). Reductive amination and lactam annulation of the respective alpha-acetoxy ketones 13 provided hydroxypyrrolizidinones (6R)- and (6S)-1 with retention of the C6-position stereochemistry. The X-ray crystallographic study of (6R)-1 indicated dihedral angles constrained within the heterocycle that were consistent with the ideal values for the i + 1 and i + 2 residues of a type II' beta-turn. Hydrogen-bonding studies on N'-methyl-N-(Boc)aminopyrrolizidin-2-one carboxamides (6R)- and (6S)-21 in DMSO-d6, demonstrated different NH chemical shift displacements and temperature coefficients for the amide and carbamate protons, indicative of solvent shielded and exposed hydrogens in a turn conformation. 6-Hydroxy pyrrolizidinone amino carboxylate 1 may thus find application as a constrained alaninylhydroxyproline dipeptide mimic. In addition, alkylation of the hydroxyl group provided orthogonally protected pyrrolizidinone amino dicarboxylate (6R)-25, demonstrating potential for expanding the diversity of these rigid dipeptide surrogates for the exploration of peptide conformation-activity relationships.     

Electrical conductivity and thermoelectric power of nickel-zinc ferrites

Electrical conductivity (σ) and thermoelectric power (Q) of polycrystalline nickel-zinc ferrites of different compositions was investigated as a function of composition and temperature. The electrical conductivity in these ferrites is explained on the basis of the hopping mechanism. Plots of log (σT) versus 10³/T are almost linear and show a transition near the curie temperature. The activation energy in the ferrimagnetic region is in general less than that in the paramagnetic region. The carrier concentration and mobility of charge carriers has been discussed as a function of composition and temperature.     

Cardioprotective Effects of 6-Gingerol against Alcohol-Induced ROS-Mediated Tissue Injury and Apoptosis in Rats

The present study investigated the cardioprotective properties of 6-gingerol against alcohol-induced ROS-mediated cardiac tissue damage in rats. Experiments were conducted on 4 groups of rats, orally treated with control, 6-gingerol (10 mg/kg body weight), alcohol (6 g/kg body weight) and combination of 6-gingerol plus alcohol for two-month. In the results, we found 6-ginger treatment to alcohol-fed rats substantially suppressed ROS production in cardiac tissue. Alcohol-induced elevated 8-OHDG and protein carbonyls which represent oxidative modification of DNA and proteins were completely reversed by 6-gingerol. This was further endorsed by restored superoxide dismutase and catalase activities with 6-gingerol against alcohol-induced loss. The elevated cardiac biomarkers (CK-MB, cTn-T, cTn-I) and dyslipidemia in alcohol-intoxicated rats was significantly reversed by 6-gingerol. Furthermore, alcohol-induced apoptosis characterized by overexpression of cytochrome C, caspase-8 and caspase-9 was diminished with 6-gingerol treatment. Transmission electron microscope images conferred the cardioprotective properties of 6-gingerol as we have seen less structural derangements in mitochondria and reappearance of myofilaments. Our findings conclude that 6-ginger effectively protect alcohol-induced ROS-mediated cardiac tissue damage, which may be due to its potent antioxidant efficacy. Therefore, 6-gingerol could be a potential therapeutic molecule that can be used in the treatment of alcohol-induced myocardial injury.     

Sugar‐Derived Di‐ and Tetrahydropyridazinones: Synthesis of New Glycosidase Inhibitors

The N‐unsubstituted D ‐arabino‐tetrahydropyridazinone 7 is a micromolar inhibitor of β‐glucosidases from sweet almonds (competitive), Caldocellum saccharolyticum (mixed), yeast α‐glucosidase (competitive), jack bean α‐mannosidase (competitive), and snail β‐mannosidase (competitive). The N‐substituted tetrahydropyridazinones 22 , 24 , and 26 are weak inhibitors of these glycosidases, and so are the dihydropyridazinones 8 and 17 – 19 , where the best inhibition was observed for 8 (K_i=56 μM for jack bean α‐mannosidase). The tetrahydropyridazinones were obtained by reduction of the corresponding dihydropyridazinones with NaCNBH₃, and the dihydropyridazinones were prepared by treatment with hydrazine or substituted hydrazines of the known and readily available D ‐threo‐pent‐2‐uluronate 11 .     

Copper catalyzed aryl amidation between Nα-Fmoc-protected amino-acid azides and aryl boronic acids

Abstract

A simple and efficient method for the synthesis of aryl amides via oxidative copper-catalyzed coupling of commercially available aryl boronic acids and bench stable N^α-protected amino-acid azides is reported. The potential utility of this protocol is demonstrated through a survey of diversely substituted aryl boronic acids and several side-chain functionalized amino-acid azides, leading to the preparation of the desired amidated products in good to excellent yields. This amide synthesis is suitable for the preparation of amides (such as peptide aryl amides and sterically hindered amino acids) that are not or hardly accessible via classical approaches.     

A new and convenient synthesis of 13,16-diazaestrone analogs

Imidazolidine-2,4-dione was chemoselectively N-alkylated at the imidic NH with several 2-(3,4-dihydro-1-naphthalenyl)ethyl-4-methylphenylsulphonates to give the corresponding imides for the first time which on selective reduction at one of the carbonyl groups followed by cyclization in PPA gave the corresponding title compounds.     

Dielectric studies of lead nitrate phosphate single crystals

Ferroelectric Lead Nitrogen Phosphate (LNP) single crystals have been synthesized using the controlled reaction between lead nitrate and orthophosphoric acid solutions by slow diffusion process in silicagel medium. The colourless transparent LNP crystals upto 6 × 4 × 3 mm³ in size have been grown at room temperature. The dielectric measurements have been carried out in the temperature range between 300 to 690 K. The effect of applied frequency on the dielectric constants and dielectric losses has been investigated. It has been observed that the mechanism of the dielectric behaviour is different in the lower and higher frequency and temperature ranges. The activation energy of the oscillators has been calculated and found to be 1.125 eV. Attempt has been made to draw some qualitative conclusions, taking in view, the existing theories of various kinds of polarizations and implications.     

Synthesis of the putative structure of eupomatilone-6

[reaction: see text] The synthesis of eupomatilone-6 (1) has been achieved by using Suzuki coupling, Sharpless asymmetric dihydroxylation, and intramolecular Horner-Wadsworth-Emmons reactions. The spectroscopic studies carried out on synthetic eupomatilone-6 do not agree with those reported for the natural product, and therefore revision of the assigned structure is warranted.     

Structural and magnetic properties of NiCuZn ferrite/SiO2 nanocomposites

Ni_0.53Cu_0.12Zn_0.35Fe₂O₄/SiO₂ nanocomposites with different weight percentages of NiCuZn ferrite dispersed in silica matrix were prepared by microwave-hydrothermal method using tetraethylorthosilicate as a precursor of silica, and metal nitrates as precursors of NiCuZn ferrite. The structure and morphology of the composites were studied using X-ray diffraction and scanning electron microscopy. The structural changes in these samples were characterized using Fourier Transform Infrared Spectrometer in the range of 400-1500 cm⁻¹. The bands in the range of 580-880 cm⁻¹ show a slight increase in intensity, which could be ascribed to the enhanced interactions between the NiCuZnFe₂O₄ clusters and silica matrix. The effects of silica content and sintering temperature on the magnetic properties of Ni_0.53Cu_0.12Zn_0.35Fe₂O₄/SiO₂ nanocomposites have been studied using electron spin resonance and vibrating sample magnetometer.