Rosane Aguiar da Silva San Gil

Two new long-chain N-alkyl imidazole derivatives, 2-(1-octadecyl-imidazol-2-yl)pyridine and 2-(furan-2-yl)-1-(octadecane-1-yl)-1H-imidazole, were synthesized via the Radziszewski reaction followed by N-alkylation. This is the first report of furan-imidazole obtained by this route using furfuraldehyde as a renewable biomass-derived precursor. FTIR, 1D/2D solution NMR, and HRMS confirmed the structural elucidation, while XRD and solid-state ¹³C CPMAS NMR corroborated the crystal structures of the precursors. Notably, previously misassigned ¹H and ¹³C chemical shifts reported in the literature for pyridine and furan-imidazole precursors were corrected. Furthermore, ¹³C CPMAS NMR spectra of those precursors are reported here for the first time. These findings expand the scope of the Radziszewski reaction and provide new insights into the structural characterization of imidazole-based systems.

Background: The pharmaceutical industry is constantly looking for a better way to ensure and improve its products' safety, quality, and effectiveness. Since there are many attributes of the drug substance and excipients that could potentially affect the Critical Quality Attributes (CQAs) of the intermediates and the final product, the evaluation of the raw material's physicochemical characteristics is crucial as they directly affect the quality, safety, efficacy, and lot-to-lot consistency. Scientists rely on methods, like HPLC, HPTLC, LC-MS, GC-MS, and NMR, to analyze these substances. The advantage of NMR is that it is considered a primary analytical method compared to other analytical techniques. Objective: This work aimed to present a simple, rapid, specific, and accurate method by proton Nuclear Magnetic Resonance spectroscopy (1H-NMR) developed to determine the activity of the antiretroviral Efavirenz’s (EFZ) Active Pharmaceutical Ingredient (API). The method was based on quantitative NMR spectroscopy (qNMR). Methods: A Bruker Avance spectrometer (11.7 Tesla, 500 MHz for 1H) with a 5mm probe was used. The 1H-NMR signal at 7.54 ppm corresponding to the analyte of interest was employed to quantify the drug. The method was validated for specificity, selectivity, intermediate precision, linearity, range of work, accuracy, and robustness. Results: The method developed was specific and linear (r2 = 0.9998) with a value between 4.30 mg/mL and 12.40 mg/mL. The relative standard deviation for accuracy and precision was 0.4% or less. The method's robustness was demonstrated by changing four different parameters, and the difference among each was 1.2% or less. The results of this work have been found to be in agreement with those obtained from High-performance Liquid Chromatography (HPLC) analysis. Conclusion: The proposed method has been found to be a valuable and practical tool for quality control. Its applicability to determining many APIs and saving solvent use and time is highlighted.

Mefloquine (MQ) is an antimalarial medication prescribed to treat or malaria prevention.. When taken by children, vomiting usually occurs, and new doses of medication frequently need to be taken. So, developing pediatric medicines using taste-masked antimalarial drug complexes is mandatory for the success of mefloquine administration. The hypothesis that binding mefloquine to an ion-exchange resin (R) could circumvent the drug’s bitter taste problem was proposed, and solid-state ¹³C cross-polarization magic angle spinning (CPMAS) NMR was able to follow MQ–R mixtures through chemical shift and relaxation measurements. The nature of MQ–R complex formation could then be determined. Impedimetric electronic tongue equipment also verified the resinate taste-masking efficiency in vitro. Variations in chemical shifts and structure dynamics measured by proton relaxation properties (e.g., T1ρ^H) were used as probes to follow the extension of mixing and specific interactions that would be present in MQ–R. A significant decrease in T1ρ^H values was observed for MQ carbons in MQ–R complexes, compared to the ones in MQ (from 100–200 ms in MQ to 20–50 ms in an MQ–R complex). The results evidenced that the cationic resin interacts strongly with mefloquine molecules in the formulation of a 1:1 ratio complex. Thus, ¹³C CPMAS NMR allowed the confirmation of the presence of a binding between mefloquine and polacrilin in the MQ–R formulation studied.

Important organic reactions require the use of catalysts. The Friedel-Crafts reactions were discovered by Charles Friedel and James Mason Crafts in 1887. They are an essential catalytic process since they are widely applied in different areas such as fuels, cleaning, and pharmacological products. The reaction is usually carried out in the presence of Lewis acids or Brønsted acids in a homogeneous medium, with the nucleophilic aromatic substrate in excess. Although there is still work in the literature on the Friedel- Crafts reaction in a homogeneous medium using metal halides, the tendency is to replace these catalysts, which generate effluents that are harmful to the environment. Heterogeneous catalysts using solid acids show advantages over homogeneous catalysts, especially concerning separating products from the reaction medium, recycling, and reusing. This paper presents a mini-review focusing on the use of solid acids in Friedel-Crafts reactions.

In this study, we have used various techniques to characterize the spectroscopic and thermal behavior of Pyrantel Pamoate (PP), an anthelmintic drug classified as an essential drug by the World Health Organization for the treatment of parasitic worm infections, as powder X-ray Diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Solid State NMR (13C CPMAS NMR), thermogravimetric analysis (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) at two different heating rates (2 and 10 K.min-1) under an inert gas flow. We analyzed a USP standard sample of PP, which allowed us to characterize it. Additionally, we examined four commercial solid formulations of PP purchased from Colombian pharmacies to provide evidence of any potential contaminants or adulteration. Our results confirmed the authenticity of the standard sample and identified PP as the active ingredient in all four Colombian products. By combining these analytical techniques, we were able to provide a comprehensive characterization of PP and potential issues with commercial formulations.

The conversion of biomass into fuel under typical refinery conditions is a promising solution to decrease carbon footprint. Herein we convert a representative compound of a new bio-petroleum, DX (1,2:3,5-di-O-isopropylidene-α-D-xylofuranose) mixture with n-hexane. Firstly fresh zeolites (Beta, ZSM-5 and USY) were explored. Beta zeolite showed a high performance in converting DX into hydrocarbons. Thus it was further modified by hydrothermal deactivation. This treatment reduced the acid site density of Beta, resulting in an improvement in aromatics, reducing gas 2-fold and coke 1-fold, and only leaving a small amount of oxygenates in the liquid fraction in the test with 20% DX.

Na tecnologia de álcali-ativação de cinzas volantes, dependendo da combinação dos ativadores, reações deletérias poderão resultar em queda na resistência com a idade. Assim, este trabalho teve como objetivo avaliar a resistência à compressão de cinzas volantes álcali-ativadas, a partir de soluções combinadas de NaOH e Ca(OH)2. Três relações molares CaO/SiO2 (C/S) foram estudadas: 0.05 (M5), 0.15 (M15) e 0.25 (M25). Resistências da ordem de 21 MPa (M15) e 19 MPa (M25) foram atingidas na idade de 7 dias. Porém, aos 28 e 91 dias as resistências foram de 8 MPa e 7 MPa, respetivamente. As amostras M5 apresentaram comportamento ascendente da resistência com a idade. Assim, a queda na resistência está condicionada a relação C/S das matrizes. Nos espectros 29Si RMN da amostra M25 o Si apresenta diminuição das espécies Q4(3Al) e Q4(2Al), estes responsáveis pelas características mecânicas das amostras ativadas.