Syntheses of aromatic aldehydes by laccase without the help of mediators

This communication reports the selective bioconversions of substituted toluenes to substituted benzaldehydes without the help of any mediators by purified laccase of indigenous fungal strain Fomes durissimus microbial type culture collection (MTCC)-1173. Molecular mass of laccase purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was found to be 74.86 kDa (～75 kDa). By using this purified laccase, selective bioconversions of 3-nitrotoluene to 3-nitrobenzaldehyde, 2-fluorotoluene to 2-fluorobenzaldehyde, 4-fluorotoluene to 4-fluorobenzaldehyde, 2-chlorotoluene to 2-chlorobenzaldehyde and 4-chlorotoluene to 4-chlorobenzaldehyde have been done without the help of mediator molecules within 1–2 hrs at room temperature and pressure with high yields (>90%). All the above bioconversions are good examples of green chemistry.     

N‐Heterocyclic Carbene Catalysis via Azolium Dienolates: An Efficient Strategy for Remote Enantioselective Functionalizations

N‐heterocyclic carbene (NHC) catalysis has emerged as a powerful strategy in organic synthesis. In recent years a number of reviews have been published on NHC‐catalyzed transformations involving Breslow intermediates, acyl azoliums, α,β‐unsaturated acyl azoliums, homoenolate equivalents, and azolium enolates. However, the azolium dienolate intermediates generated by NHCs have been employed in asymmetric synthesis only very recently, especially in cycloadditions dealing with remote functionalization. This Minireview highlights all the developments and the new advances in NHC‐catalyzed asymmetric cycloaddition reactions involving azolium dienolate intermediates.     

Advancing MXene Electrocatalysts for Energy Conversion Reactions: Surface,Stoichiometry, and Stability

MXenes, due to their tailorable chemistry and favourable physical properties, have great promise in electrocatalytic energy conversion reactions. To exploit fully their enormous potential, further advances specific to electrocatalysis revolving around their performance, stability, compositional discovery and synthesis are required. The most recent advances in these aspects are discussed in detail: surface functional and stoichiometric modifications which can improve performance, Pourbaix stability related to their electrocatalytic operating conditions, density functional theory and advances in machine learning for their discovery, and prospects in large scale synthesis and solution processing techniques to produce membrane electrode assemblies and integrated electrodes. This Review provides a perspective that is complemented by new density functional theory calculations which show how these recent advances in MXene material design are paving the way for effective electrocatalysts required for the transition to integrated renewable energy systems.     

Validation of a Stability-Indicating LC Method for Assay of Ezetimibe in Tablets and for Determination of Content Uniformity

A simple, precise, and accurate HPLC method has been developed and validated for assay of ezetimibe in tablets and for determination of content uniformity. Reversed-phase liquid chromatographic separation was achieved by use of phosphoric acid (0.1%, v/v)–acetonitrile 50:50 (v/v) as mobile phase. The method was validated for specificity, linearity, precision, accuracy, robustness, and solution stability. The specificity of the method was determined by assessing interference from the placebo and by stress testing of the drug (forced degradation). Response was a linear function of drug concentration in the range 20–80 μg mL⁻¹ (r = 0.9999). Intraday and interday system and method precision were determined. Accuracy was between 100.8 and 102.7%. The method was found to be robust, and was suitable for assay of ezetimibe in a tablet formulation and for determination of content uniformity. An erratum to this article can be found at     

Validated LC Method for Simultaneous Analysis of Tramadol Hydrochloride and Aceclofenac in a Commercial Tablet

This paper describes development and validation of a high-performance liquid chromatographic method for simultaneous analysis of tramadol hydrochloride (TR) and aceclofenac (AC) in a tablet formulation. When the combination formulation was subjected to ICH-recommended stress conditions, adequate separation of TR, AC, and the degradation products formed was achieved on a C₁₈ column with 65:35 (v/v) 0.01 M ammonium acetate buffer, pH 6.5—acetonitrile as mobile phase at a flow rate of 1 mL min^?1. UV detection was performed at 270 nm. The method was validated for specificity, linearity, LOD and LOQ, precision, accuracy, and robustness. The method was specific against placebo interference and also during forced degradation. The linearity of the method was investigated in the concentration ranges 15–60 μg mL^?1 (r = 0.9999) for TR and 40–160 μg mL^?1 (r = 0.9999) for AC. Accuracy was between 98.87 and 99.32% for TR and between 98.81 and 99.49% for AC. Because degradation products were well separated from the parent compounds, the method was stability-indicating.     

Ferrocenyl,Alkyl, and Aryl‐Pyrido[2,3‐d]Pyrimidines as Vasorelaxant of Smooth Muscle of Rat Aorta via cAMP Conservation Through Phosphodiesterase Inhibition

New pyrido[2,3‐d]pyrimidines 11 , 12 , 13 , and 21 have been synthesized. The vasorelaxant effect on smooth muscle isolated from rat aorta, via PDEs inhibition, of these compounds along with other pyrido[2,3‐d]pyrimidines 14 , 15 , 16 , 17 , 18 , 19 , 20 reported earlier by our group, has also been determined. These pyrido[2,3‐d]pyrimidines 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 were synthesized by the reaction of ferrocenyl‐ethynyl ketones ( 1 , 2 , 3 , 4 ) or α‐alkynyl ketones ( 5 , 6 , 7 , 8 , 9 , 10 ) with 6‐amino‐1,3‐dimethyluracil using [Ni(CN)₄]^?4 as an active catalytic species, formed in situ in a Ni(CN)₂/NaOH/H₂O/CO/KCN aqueous system. Evaluation of the vasorelaxant effect of compounds 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 demonstrated that all compounds relax the tissue in a concentration‐dependent manner. The structural changes do not alter the effectiveness; however, there are differences related to potency expressed as EC₅₀. Compounds 12 (7‐ferrocenyl‐1,3‐dimethyl‐5‐(m‐tolyl)‐pyrido[2,3‐d]pyrimidine) and 13 (7‐ferrocenyl‐1,3‐dipropyl‐5‐(4‐metoxyphenyl)‐pyrido[2,3‐d]pyrimidine) were the most potent compounds, even more than rolipram, reference drug; the EC₅₀ was 0.41 ± 0.02 μM and 0.81 ± 0.11 μM for 12 and 13 , correspondingly. The EC₅₀ of compounds 15 (7‐ferrocenyl‐1,3‐dimethyl‐5‐phenyl‐pyrido[2,3‐d]pyrimidine), 14 (7‐ferrocenyl‐5‐(3,5‐dimethoxyphenyl)‐1,3‐dimethylpyrido[2,3‐d]pyrimidine), and 19 (5‐n‐butyl‐7‐ethyl‐1,3‐dimethylpyrido[2,3‐d]pyrimidine) was similar to EC₅₀ of rolipram. Compounds 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 significantly induce concentration‐dependent vasorelaxation in endothelium‐intact aortic rings. In addition, the relaxation responses to each compound in either endothelium‐intact or endothelium denuded aortic rings were comparable, suggesting that removal of the functional endothelium has no significant influence on its intrinsic vasorelaxant activity. In vitro capability of conserving cyclic‐AMP or cyclic‐GMP (adenosine and guanosine 3′, 5′‐cyclic monophosphate) via PDE inhibition for compounds 12 , 13 , 14 , 15 and 19 was evaluated. Compounds 15 and 19 show the highest percent inhibition effect (94.83% and 83.98%, respectively) for the decomposition of c‐AMP. Docking studies showed that the compound 15 was selective for the inhibition of PDE‐4.     

Some novel organometallic Mn<Superscript>III</Superscript> complexes with porphine and 1,6-diaminohexane

A novel series of Mn^III complexes with 5,10,15,20-tetra(p-tolylporphine) and 1,6-diaminohexane has been synthesized. These complexes have been characterized by UV/Vis, IR, ESI-mass spectra, elemental analysis, conductivity and magnetic susceptibility measurements. These Mn^III porphyrins exhibited a blue shift in soret band in comparison to non-metallated porphyrins. The molar conductance values of these complexes show their non-electrolytic nature in ethanol. The tentative structures have also been proposed. All the complexes have good level of water solubility due to which they may have medicinal as well as other valuable biological applications.     

Sensor biocompatibility: final frontier in bioanalytical measurement

Chemical and biosensors operate as direct sample contact systems; as such, the response of the biomatrix to their presence is as important as their response to the targeted analyte. There needs to be greater research emphasis on the response of biofluids to sensors because of the impact on sensor performance. Mainly, this is the result of deposited biolayers through the adsorption of colloids and proteins, followed by a more complex surface-active system: whole cells. Sensor surface engineering and controlled sample presentation through fluidics are likely to be able to mitigate some of these effects. Overall there needs to be a convergence with rapidly evolving research strategies in biomaterials if sensors are to make the full transition from the laboratory to the real world.