Novel approach to detect Barium in Gunshot Residue using Handheld Device: A Forensic Application

The present manuscript describes an innovative handheld device for rapid detection of Barium (Ba2+) in Gunshot Residue (GSR) based on the use of Gold nanomaterial capped with sodium malonate. The...

Expeditious Synthesis of 2-Amino-4H-chromenes and 2-Amino-4H-pyran-3- carboxylates Promoted by Sodium Malonate

Background: Chromenes and pyran annulated heterocycles are the most common frameworks existing in various biologically active molecules. Due to their beneficial and biological properties, they are eyecatching synthetic targets in the arsenal of organic chemistry. Thus, finding green and efficient methods, as well as searching for a new catalyst for the synthesis of these heterocycles is of interest to organic chemistry researchers. Objective: Sodium malonate as a readily available catalyst was employed aimed at the multicomponent synthesis of numerous 2-amino-4H-chromenes and 2-amino-4H-pyrans in water as a green medium reaction. Methods: The reaction was performed via treatment of aldehydes (1 mmol) with malononitrile/ethyl cyanoacetate (1 mmol) and β-dicarbonyl compounds (1 mmol)/or resorcinol (1 mmol) in water (4 mL) in the presence of sodium malonate (10 mol %) at 70°C. On completion of the reaction (monitored by TLC analysis), the reaction mixture was gradually cooled at room temperature, and the resulting precipitates were collected by filtration, washed with cold ethanol and air-dried to give the corresponding pure products. The solvent was evaporated from the filtrate to recover the catalyst, and the catalyst was reused for subsequent reactions. Results: In the initial stages, we explored the best reaction conditions using three-component reaction of benzaldehyde, malononitrile, and dimedone as the model reaction. The effects of catalyst loading, temperature, and solvents were explored for this reaction. It was found that the best results were obtained for the synthesis of 2-amino-4H-chromenes and 2-amino-4H-pyran when the three-component reaction was carried out with equivalent molar quantities of each of the reactants in water containing 10 mol% sodium malonate at 70°C for 15 min in 96% yield. After finding optimal conditions, these conditions apply to other reactants and the target heterocyclic products were obtained with excellent yields. Conclusion: This study describes an efficient, environmentally benign, and clean one-pot, three-component synthesis of 2-amino-4H-chromenes and 2-amino-4H-pyran-3-carboxylates in the presence of sodium malonate as the commercially available catalyst in an aqueous medium at 70°C. High yields, mild reaction conditions, relatively shorter reaction times, use of simple reagents, and no requirement of the ultrasound, microwave, and ball milling techniques are the salient features and benefits of the present method. In addition, the present process is smooth and green.

Insight into the Claisen condensation of methyl acetate and dimethyl carbonate to dimethyl malonate

A mechanistic model for the Claisen condensation of methyl acetate and dimethyl carbonate in the presence of sodium methoxide to sodium malonate and further protonation to dimethyl malonate is proposed based on experimental and computational results.

Expression, purification, crystallization and preliminary crystallographic analysis of a GH20 β-N-acetylglucosaminidase from the marine bacteriumVibrio harveyi

Vibrio harveyiβ-N-acetylglucosaminidase (VhGlcNAcase) is a new member of the GH20 glycoside hydrolase family responsible for the complete degradation of chitin fragments, withN-acetylglucosamine (GlcNAc) monomers as the final products. In this study, the crystallization and preliminary crystallographic data of wild-typeVhGlcNAcase and its catalytically inactive mutant D437A in the absence and the presence of substrate are reported. Crystals of wild-typeVhGlcNAcase were grown in 0.1 Msodium acetate pH 4.6, 1.4 Msodium malonate, while crystals of the D437A mutant were obtained in 0.1 Mbis-tris pH 7.5, 0.1 Msodium acetate, 20% PEG 3350. X-ray data from the wild-type and the mutant crystals were collected at a synchrotron-radiation light source and were complete to a resolution of 2.5 Å. All crystals were composed of the same type of dimer, with the substrateN,N′-diacetylglucosamine (GlcNAc2or diNAG) used for soaking was cleaved by the active enzyme, leaving only a single GlcNAc molecule bound to the protein.