An efficient microwave accelerated three component reaction of phenacyl azides and pyridinium phenacyl salts: A facile greener approach to 2-amino-2-ene-1,4-diones/pyrrolidin-2-ones

Abstract

A mild and efficient base promoted, microwave assisted, green synthesis of 2-amino-2-ene-1,4-diones has been described by the decomposition of phenacyl azides followed by treatment with pyridinium salts of phenacyl bromides in aqueous media. A diverse range of substrates bearing electron-releasing and electron-withdrawing substituents were well tolerated and delivered corresponding 2-amino-2-ene-1,4-diones in good yields. Synthesized 2-amino-2-ene-1,4-diones have been further explored in the synthesis of various substituted 4-hydroxypyrrolidin-2-ones.     

Zirconyl nitrate mediated regioselective ring opening of epoxides and aziridines: an easy synthesis of β-nitrato-alcohols and -sulfonamides

Epoxides and aziridines are cleaved efficiently and regioselectively in the presence of zirconyl nitrate at room temperature to afford the corresponding β-nitrato-alcohols and -sulfonamides, respectively, in high yields.     

Ultrathin layered myoglobin-polyion films functional and stable at acidic pH values

Cross-linking of myoglobin (Mb) promoted by 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide within films of polystyrene sulfonate after layer-by-layer self-assembly provided remarkable stabilization. Cross-linking greatly improved adhesion of the films to fused silica slides and allowed extensive optical studies over a wide pH range. Circular dichroism and visible absorbance spectra showed that Mb retained its native conformation when films were placed in solutions of pH as low as 2 and up to pH 11. Linear dichroism revealed an average orientation of the Mb iron heme cofactors of 58 degrees to the film normal. High concentrations of urea did denature the protein in the films, however. At pH 1, Mb in solution is fully unfolded but retained considerable alpha-helical content in the cross-linked films. Both the polyion film environment and cross-linking seem to play roles in stabilizing protein secondary structure and function at low pH. Cross-linked myoglobin-polyion films on pyrolytic graphite electrodes were used in strongly acidic solutions for the electrochemical catalytic reduction of trichloracetic acid, hydrogen peroxide, and oxygen. The pH-dependent catalytic reduction of trichloracetic acid was faster in 0.1 M HCl than in the medium pH range.     

LC-PDA and LC-ESI-MS separation and determination of process-related substances arising from stilbene-type fluorescent whitening agents. Application to monitoring of their photodegradation products in industrial effluents and aqueous environmental systems

A simple and rapid gradient elution high-performance liquid chromatographic method using photodiode array and electrospray ionization mass spectrometric detectors was developed for separation and determination of the process-related substances and photodegradation products of stilbenesulfonic acids, viz. 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNSDA), 4-amino-4'-nitrostilbene-2,2'-disulfonic acid (ANSDA), and 4,4'-diaminostilbene-2,2'-disulfonic acid (DASDA) in industrial waste waters. Gradient elution was carried out using ammonium acetate and acetonitrile as mobile phase and an Inertsil-ODS 3V column for separation. The negative-ion electrospray ionization mass spectra containing [M-H]- ions of sulfonic acids allowed molecular mass determination of unknowns and the structures were proposed on the basis of the fragment ions in the MS/MS spectra.     

Simultaneous determination of niacin and its metabolites—nicotinamide,nicotinuric acid and N‐methyl‐2‐pyridone‐5‐carboxamide—in human plasma by LC‐MS/MS and its application to a human pharmacokinetic study

An LC‐MS/MS method for the simultaneous quantitation of niacin (NA) and its metabolites, i.e. nicotinamide (NAM), nicotinuric acid (NUA) and N‐methyl‐2‐pyridone‐5‐carboxamide (2‐Pyr), in human plasma (1 mL) was developed and validated using nevirapine as an internal standard (IS). Extraction of the NA and its metabolites along with the IS from human plasma was accomplished using a simple liquid–liquid extraction. The chromatographic separation of NA, NAM, NUA, 2‐Pyr and IS was achieved on a Hypersil‐BDS column (150 ¥ 4.6 mm, 5 mm) column using a mobile phase consisting of 0.1% formic acid : acetonitrile (20:80 v/v) at a flow rate of 1 mL/min. The total run time of analysis was 2 min and elution of NA, NAM, NUA, 2‐Pyr and IS occurred at 1.37, 1.46, 1.40, 1.06 and 1.27 min, respectively. A detailed validation of the method was performed as per the FDA guidelines and the standard curves were found to be linear in the range of 100–20000 ng/mL for NA; 10–1600 ng/mL for NUA and NAM and 50–5000 ng/mL for 2‐Pyr with mean correlation coefficient of ≥0.99 for each analyte. The method was sensitive, specific, precise, accurate and suitable for bioequivalence and pharmacokinetic studies. The developed assay method was successfully applied to a pharmacokinetic study in humans. Copyright © 2010 John Wiley & Sons, Ltd.     

Kinetics and mechanism of certain benzoylation reactions under Vilsmeier–Haack conditions using benzamide and oxychloride in acetonitrile medium

Vilsmeier–Haack (VH) benzoylation reactions with benzaldehydes and acetophenones in acetonitrile medium obeyed second‐order reaction kinetics. Under kinetic conditions, the reactions afforded benzoyl derivatives irrespective of the nature of oxychloride (POCl₃ or SOCl₂) used for the preparation of VH reagent along with benzamide. The present finding is advantageous to understand the nature of reactive species as well as the mechanism of benzoylation. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 69–80, 2013     

Sensitive and selective liquid chromatography–tandem mass spectrometry method for the determination of metoclopramide in human plasma: application to a bioequivalence study

A simple, sensitive and rapid method has been developed and validated for determination of the metoclopramide (MCP) in 100 μL human plasma. The analytical procedure involves a liquid–liquid extraction method using tramadol as an internal standard (IS). Chromatographic separation was carried out on a HyPURITY ADVANCE column using a mobile phase consisting of acetonitrile and 10 mm ammonium acetate buffer in the ratio of 80:20 (v/v) at a flow rate of 0.3 mL/min. The total run time of analysis was 2.5 min and elution of MCP and IS occurred at 0.9 and 1.3 min, respectively. A linear response function was established for the range of concentrations 0.53–42.07 ng/mL (r > 0.99). The intra‐ and inter‐day precision values for MCP met the acceptance as per FDA guidelines. MCP was stable in a battery of stability studies viz., bench‐top, auto‐sampler and freeze–thaw cycles. The developed assay method was successfully applied to an oral bioequivalence study in humans. Copyright © 2010 John Wiley & Sons, Ltd.     

The reactivity of the double bond in coumarins and related unsaturated carbonyl compounds

Proceedings - Mathematical Sciences - The addition of cyanoacetamide to the double bond of 7-methoxy and 7-hydroxycoumarins is very slow and it is attributed to the influence of the substituents...     

Total Synthesis of a Mevinic Acid Analog

Total synthesis of mevinic acid analog 1 has been achieved efficiently starting from chiral 2,3‐O‐isopropylidene‐D ‐glyceraldehyde ( 2 ). The synthesis involves Mitsunobu reaction and Evans' intramolecular oxa‐Michael syn‐addition reactions as key steps.     

A concise synthesis of polyhydroxydihydrochalcones and homoisoflavonoids

A general and single step synthesis of polyhydroxydihydrochalcones from the readily available phenols and dihydrocinnamic acids using BF₃·Et₂O is described. The method allows the synthesis of a wide range of compounds with multiple phenolic hydroxyls and other substituents. These dihydrochalcones are converted into homoisoflavonoids by DMF/PCl₅ and the methodology has been applied to the synthesis of naturally occurring phloretin and 5,7-dihydroxy-3-[(4-hydroxyphenyl)methyl]-4H-chromen-4-one. The antioxidant activity of dihydrochalcones and homoisoflavonoids was determined by superoxide free radical (NBT) and DPPH free radical scavenging methods. Polyhydroxydihydrochalcones 3c, 3f, 3g and homoisoflavonoids 4c, 4f, 4g displayed excellent antioxidant activity.