Facile and Efficient Acetylation of Primary Alcohols and Phenols with Acetic Anhydride Catalyzed by Dried Sodium Bicarbonate

Light-Driven Two-Step Preparation of 4-Chromanone Fused to Estrone Derivatives

A protocol involving the irradiation of some 3-(2-alkenyl)estrone and 3-(2-alkenyl)-17-norestrone derivatives under a nitrogen atmosphere in organic solvents (both hexane and MeOH) followed by base-mediated intramolecular oxa-Michael cyclization reaction was investigated under steady-state conditions. The solvent effect and nature of the acyl group on the preparative photoreaction were studied and the multiplicity of the excited state was also demonstrated. The ortho-regioisomers were obtained in modest to good yields. Intramolecular based-mediate cyclization reaction of these synthons led to the formation of a set of novel substituted 4-chromanone moieties fused to estrone (and 17-norestrone) in good yields. This two-step sequential procedure involving a photochemical/intramolecular thermal cyclization strategy will be useful for the preparation of wide heterocyclic-fused-steroid compounds.

Determination of biogenic amines in chicken, beef, and mutton by dansyl chloride microwave derivatization in Malaysia

In this study, an improved dansyl-chloride derivatization technique using a microwave synthesizer was used for the qualitative and quantitative analyses of biogenic amine in the fresh meat samples. The derivatization technique was optimized in terms of temperature, reaction time, and spinning speed. The derivatization method together with a validated reversed-phase HPLC-DAD method was used for the determination of biogenic amines in chicken, beef, and mutton sold in the wet market. The results of the analyses showed that tryptamine, putrescine, and histamine were generally detected in all the three types of meat. Higher levels of histamine were found in chicken and beef. However, low levels of histamine were observed in mutton. Tyramine was either detected low or moderate in all the three types of meat. The biogenic amines of the fresh meat sold in the wet market is generally higher than the reported values. The mechanisms of biogenic amines-dansyl-chloride formation were investigated and proposed. PRACTICAL APPLICATION: The biogenic amine derivatization method was improved. The improved derivatization method can be potentially used for various food products beside meats for routine biogenic amine analyses due to its fast analysis time and simplicity. High levels of biogenic amines were generally found in the meat sold in the wet markets. However, proper handling of the raw meat can reduce the risk of infection.

A Stoichiometric Solvent-Free Protocol for Acetylation Reactions

Considering the remarkable relevance of acetylated derivatives of phenols, alcohols, and aryl and alkyl thiols in different areas of biology, as well as in synthetic organic chemistry, a sustainable solvent-free approach to perform acetylation reactions is proposed here. Acetylation reactions are classically performed using excess of acetic anhydride (Ac2O) in solvent-free conditions or by eventually working with stoichiometric amounts of Ac2O in organic solvents; both methods require the addition of basic or acid catalysts to promote the esterification. Therefore, they usually lead to the generation of high amounts of wastes, which sensibly raise the E-factor of the process. With the aim to develop a more sustainable system, a solvent-free, stoichiometric acetylation protocol is, thus, proposed. The naturally occurring phenol, thymol, can be converted to the corresponding-biologically active-ester with good yields, in the presence of 1% of VOSO4. Interestingly, the process can be efficiently adopted to synthesize other thymyl esters, as well as to perform acetylation of alcohols and aryl and alkyl thiols. Remarkably, a further improvement has been achieved replacing Ac2O with its greener alternative, isopropenyl acetate (IPA).

Trimethylsilyl Esters as Novel Dual-Purpose Protecting Reagents

Trimethylsilyl esters, AcOTMS, BzOTMS, TCAOTMS, etc., are inexpensive and chemically stable reagents that pose a negligible environmental hazard. Such compounds prove to serve as efficient dual-purpose reagents to respectively achieve acylation and trimethylsilylation of alcohols under acidic or basic conditions. Herein, a detailed study on protection of various substrates and new methodological investigations is described.

Oxidant-reactive carbonous moieties in dissolved organic matter: Selective quantification by oxidative titration using chlorine dioxide and ozone

The application of oxidants for disinfection or micropollutant abatement during drinking water and wastewater treatment is accompanied by oxidation of matrix components such as dissolved organic matter (DOM). To improve predictions of the efficiency of oxidation processes and the formation of oxidation products, methods to determine concentrations of oxidant-reactive phenolic, olefinic or amine-type DOM moieties are critical. Here, a novel selective oxidative titration approach is presented, which is based on reaction kinetics of oxidation reactions towards certain DOM moieties. Phenolic moieties were determined by oxidative titration with ClO₂ and O₃ for five DOM isolates and two secondary wastewater effluent samples. The determined concentrations of phenolic moieties correlated with the electron-donating capacity (EDC) and the formation of inorganic ClO₂-byproducts (HOCl, ClO₂^-, ClO₃^-). ClO₂-byproduct yields from phenol and DOM isolates and changes due to the application of molecular tagging for phenols revealed a better understanding of oxidant-reactive structures within DOM. Overall, oxidative titrations with ClO₂ and O₃ provide a novel and promising tool to quantify oxidant-reactive moieties in complex mixtures such as DOM and can be expanded to other matrices or oxidants.

Neuropharmacological Activity of the New Piperazine Derivative 2-(4-((1- Phenyl-1H-Pyrazol-4-yl)Methyl)Piperazin-1-yl)Ethyl Acetate is Modulated by Serotonergic and GABAergic Pathways

BACKGROUND

Pharmacological treatments for mental disorders, such as anxiety and depression, present several limitations and adverse effects. Therefore, new pharmacotherapy with anxiolytic and antidepressant potential is necessary, and the study of compounds capable of interacting with more than one pharmacological target may provide new therapeutic options.

OBJECTIVES

In this study, we proposed the design, synthesis of a new compound, 2-(4-((1-phenyl-1H-pyrazol-4-yl)methyl)piperazin-1-yl)ethyl acetate (LQFM192), pharmacological evaluation of its anxiolytic-like and antidepressant-like activities, as well as the possible mechanisms of action involved.

METHODS

Administration of LQFM192 was carried out prior to the exposure of male Swiss mice to behavioral tests, such as the elevated plus-maze and forced swimming test. The involvement of the serotonergic system was studied by pretreatment with WAY-100635 or p-chlorophenylalanine (PCPA) and the involvement of the benzodiazepine site of the GABAA receptor by pretreatment with flumazenil.

RESULTS

The treatment with LQFM192 at doses of 54 and 162 µmol/kg demonstrated anxiolyticlike activity that was blocked by WAY-100635, PCPA, and flumazenil pretreatments. The potential antidepressant-like activity was visualized at the same doses and blocked by WAY-100635 and PCPA.

CONCLUSION

In summary, the anxiolytic-like activity of LQFM192 is mediated by the serotonergic system and the benzodiazepine site of the GABAA receptor, and the antidepressant-like activity through the serotonergic system.

Chemoenzymatic Synthesis of 5-Methylpsilocybin: A Tryptamine with Potential Psychedelic Activity

A novel analogue of psilocybin was produced by hybrid chemoenzymatic synthesis in sufficient quantity to enable bioassay. Utilizing purified 4-hydroxytryptamine kinase from Psilocybe cubensis, chemically synthesized 5-methylpsilocin (2) was enzymatically phosphorylated to provide 5-methylpsilocybin (1). The zwitterionic product was isolated from the enzymatic step with high purity utilizing a solvent-antisolvent precipitation approach. Subsequently, 1 was tested for psychedelic-like activity using the mouse head-twitch response assay, which indicated activity that was more potent than the psychedelic dimethyltryptamine, but less potent than that of psilocybin.

Peracylation Coupled with Tandem Mass Spectrometry for Structural Sequencing of Sulfated Glycosaminoglycan Mixtures without Depolymerization

The structures of glycosaminoglycans (GAGs), especially the patterns of modification, are crucial to modulate interactions with various protein targets. It is very challenging to determine the fine structures using liquid chromatography-mass spectrometry (LC-MS) due in large part to the gas-phase sulfate losses upon collisional activation. Previously, our group reported a method for fine structure analysis that required permethylation of the GAG oligosaccharide. However, uncontrolled depolymerization during the permethylation process due to esterification of uronic acid lowers the reliability of the method to resolve structures of GAGs, especially for larger oligosaccharides. Here, we describe a simplified derivatization method using propionylation and desulfation. The oligosaccharides have all hydroxyl and amine groups protected with propionyl groups and then have sulfate groups removed to generate unprotected hydroxyl and amine groups at all sites that were previously sulfated. This derivatized oligosaccharide generates informative fragments during collision-induced dissociation that resolve the original sulfation patterns. This method is demonstrated to enable accurate determination of sulfation patterns of even the highly sulfated pentasaccharide fondaparinux by MS² and MS³. Using a mixture of dp6 from porcine heparin, we demonstrate that this method allows for structural characterization of complex mixtures, including clear chromatographic separation and sequencing of structural isomers, all at high yields without evidence of depolymerization. This represents a marked improvement in the reliability to structurally characterize GAG oligosaccharides over permethylation-based derivatization schemes.

Succinyl-DOTOPA: An effective triradical dopant for low-temperature dynamic nuclear polarization with high solubility in aqueous solvent mixtures at neutral pH

We report the synthesis of the nitroxide-based triradical compound succinyl-DOTOPA and the characterization of its performance as a dopant for dynamic nuclear polarization (DNP) experiments in frozen solutions at low temperatures. Compared with previously described DOTOPA derivatives, succinyl-DOTOPA has substantially greater solubility in glycerol/water mixtures with pH > 4 and therefore has wider applicability. Solid state nuclear magnetic resonance (ssNMR) measurements at 9.39 T and 25 K, with magic-angle spinning at 7.00 kHz, show that build-up times of DNP-enhanced, cross-polarized ¹³C ssNMR signals are shorter and that signal amplitudes are larger for glycerol/water solutions of L-proline containing succinyl-DOTOPA than for solutions containing the biradical AMUPol, with electron spin concentrations of 15 mM or 30 mM, resulting in greater net sensitivity gains from DNP. In similar measurements at 90 K, AMUPol yields greater net sensitivity, apparently due to its longer electron spin-lattice and spin-spin relaxation times. One- and two-dimensional ¹³C ssNMR measurements at 25 K on the complex of the 27-residue peptide M13 with the calcium-sensing protein calmodulin, in glycerol/water with 10 mM succinyl-DOTOPA, demonstrate the utility of this compound in DNP-enhanced ssNMR studies of biomolecular systems.

An improved in situ acetylation with dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry for the sensitive determination of phenols in mainstream tobacco smoke

Phenols in tobacco smoke can adversely affect health with serious consequences that include cardiovascular toxicity, tumor promotion and genotoxic activity. Hence, an improved method involving in situ acetylation and dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for the determination of 39 phenols in mainstream tobacco smoke (MTS). The in situ acetylation was optimized using four protocols, after which the effects of experimental variables on acetylation efficiency were studied using a multifactorial experimental design. The optimum conditions were found to involve an initial 75 μL volume of acetic anhydride, 140 mg of NaHCO₃ and 72 mg of K₂CO₃. The phenolic acetates were then subjected to DLLME, after which they were identified and quantified by GC-MS. A total of 32 additional phenols were tentatively identified. Good linearity was observed with R > 0.999 and each lack-of-fit P > 0.05. The relative recoveries were in the range of 94.8-104.3% with repeatabilities and reproducibilities less than 5.5% and 6.8%, respectively. The limits of detection ranged from 1.12 to 1.74 ng cig^-1, with high enrichment factors between 87 and 144. This method was applied to the MTS from three commercial cigarettes with different tar levels. The results provide valuable information for assessing the risks of phenols.

Phenalenones from a Marine-Derived Fungus Penicillium Sp

Six new phenalenone derivatives (1–6), along with five known compounds (7–11) of the herqueinone class, were isolated from a marine-derived fungus Penicillium sp. The absolute configurations of these compounds were assigned based on chemical modifications and their specific rotations. 4-Hydroxysclerodin (6) and an acetone adduct of a triketone (7) exhibited moderate anti-angiogenetic and anti-inflammatory activities, respectively, while ent-peniciherqueinone (1) and isoherqueinone (9) exhibited moderate abilities to induce adipogenesis without cytotoxicity.

5-(6-Hydroxy-6-methyl-5-oxoheptan-2-yl)-2-methyl Phenyl Acetate

We synthesized a novel compound, 5-(6-hydroxy-6-methyl-5-oxoheptan-2-yl)-2-methylphenyl acetate, in a good yield by oxidation of 1-O-acetyl-xanthorrizol using potassium permanganate in acidic condition. The structure was elucidated by Fourier Transform Infrared (FTIR), 1H-Nuclear Magnetic Resonance (NMR) and 13C-NMR, two-dimensional (2D)-HSQC, Distortionless Enhancement by Polarization Transfer (DEPT), 2D-Heteronuclear Multiple Bond Correlation (HMBC), and High-Resolution Mass Spectra (HRMS) spectral data.

Derivatives of the Lignan 7'-Hydroxymatairesinol with Antioxidant Properties and Enhanced Lipophilicity

The lignan 7'-hydroxymatairesinol (1), extracted from the knotwoods of fir (Abies alba), spruce (Picea abies), and Douglas fir (Pseudotsuga menziesii), exhibited unexpected reactivity when esterification reactions were attempted on the hydroxy group at position C-7'. To circumvent the rapid intramolecular cyclization procedure, leading quantitatively to the lignan conidendrin (7), a simple strategy for 7'-esterification of 1 under mild conditions (three steps, up to 80% overall yield) was developed. Compared to hydroxymatairesinol (1) (log K'_w = 1.49), the derivatives (2-5) had increased lipophilicity with log K'_w > 3.1, as determined by a UHPLC method. Compounds 1-5 exhibited potent antioxidant properties in the same range as the standards ascorbic acid and α-tocopherol (IC₅₀ = 20-25 μM) and higher than that of BHT using a DPPH radical-scavenging assay.

Direct Visualization of Neurotransmitters in Rat Brain Slices by Desorption Electrospray Ionization Mass Spectrometry Imaging (DESI - MS)

Mass spectrometry imaging (MSI) of neurotransmitters has so far been mainly performed by matrix-assisted laser desorption/ionization (MALDI) where derivatization reagents, deuterated matrix and/or high resolution, or tandem MS have been applied to circumvent problems with interfering ion peaks from matrix and from isobaric species. We herein describe the application of desorption electrospray ionization mass spectrometry imaging (DESI)-MSI in rat brain coronal and sagittal slices for direct spatial monitoring of neurotransmitters and choline with no need of derivatization reagents and/or deuterated materials. The amino acids γ-aminobutyric (GABA), glutamate, aspartate, serine, as well as acetylcholine, dopamine, and choline were successfully imaged using a commercial DESI source coupled to a hybrid quadrupole-Orbitrap mass spectrometer. The spatial distribution of the analyzed compounds in different brain regions was determined. We conclude that the ambient matrix-free DESI-MSI is suitable for neurotransmitter imaging and could be applied in studies that involve evaluation of imbalances in neurotransmitters levels. Graphical Abstract ᅟ.

Strategies to Overcome Heparins' Low Oral Bioavailability

Even after a century, heparin is still the most effective anticoagulant available with few side effects. The poor oral absorption of heparins triggered the search for strategies to achieve oral bioavailability since this route has evident advantages over parenteral administration. Several approaches emerged, such as conjugation of heparins with bile acids and lipids, formulation with penetration enhancers, and encapsulation of heparins in micro and nanoparticles. Some of these strategies appear to have potential as good delivery systems to overcome heparin’s low oral bioavailability. Nevertheless, none have reached the market yet. Overall, this review aims to provide insights regarding the oral bioavailability of heparin.

The first vinyl acetate mediated organocatalytic transesterification of phenols: a step towards sustainability

A practical and efficient method for vinyl ester based transesterification of phenols under organocatalytic conditions has been described.