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Extraction and Chemistry of Rubber Allergens
Published in Robert N. Phalen, Howard I. Maibach, Protective Gloves for Occupational Use, 2023
Single-use medical gloves were surveyed for allergenic rubber accelerators by Knudsen et al.39 Gloves were extracted with acetone and extracts were evaporated to dryness and reconstituted in chloroform. Extracts were screened qualitatively using high-performance thin-layer chromatography (HPTLC) by developing the plates with dithizone and then with 2,6-Dichloroquinone-4-chlorimide for identification of carbamates, thiurams, and MBT. The accelerator detection limit was approximately 100–200 µg/g of the glove. Extracts were acylated using trifluoroacetic anhydride and analyzed on a GC equipped with a flame ionization detector (GC-FID), and chemical identification was confirmed using a GC-mass spectrometer (GC-MS). The reported limits of detection were between 10 and 20 µg/g of the glove. HPTLC can distinguish between thiurams and their corresponding carbamates, but the GC methods cannot distinguish between these compounds because of the derivatization procedure. Multiple types of accelerators were reported to be present in the gloves, with ZDEC, ZDBC, and zinc MBT (ZMBT) being the most prevalent.
Halogen Labeled Compounds (F, Br, At, Cl) *
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
A new method of radiobromination was developed by Coenen et al.270, 271 using N- chlorotetrafluorosuccinimide and 77Br— in trifluoroacetic anhydride. 77Br-Bromoto-luene and other benzene derivatives were synthesized in radiochemical yields of 1.8 to 63% with carrier-free bromide.
Development and Evaluation
Published in Joseph Chamberlain, The Analysis of Drugs in Biological Fluids, 2018
One of the first practical steps in the development of a new method is to examine the known chemical characteristics of the drug. In the pharmaceutical industry, a useful first move is to to consult with the chemist who first synthesized the compound. Often, the chemist will have considerable structural information on the drug including NMR and mass spectra, which may seem irrelevant to our immediate needs. However, the chemist should also have ultraviolet spectra, which may be useful as an assay in its own right, or may serve as the detection system in some sort of chromatography. The synthetic chemist will certainly have some thin-layer chromatography data and although such data will have been compiled with a view to separating precursors, side products and degradation products from the compound of interest, the same systems may be useful in the separation and detection of metabolites. Apart from the analytical data the chemist may have, more importantly, he should have valuable information on the compound's stability and may even be aware of unusual reactions leading to specific colored or fluorescent degradation products. The chemist will be able to point to specific functional groups with unusual activity, or to steric hindrances preventing what would seem an obvious derivative from forming. An example of this can be seen in the analysis of a series of ß-agonists and antagonists. The relatively unhindered amines and hydroxyl groups of propranolol, labetalol, and atenolol are readily derivatized with trifluoroacetic anhydride. However, when a similar method was applied to penbutolol, the derivatives proved extremely unstable and although a method could be carried out with extreme care, it did not have the robustness of the method applicable to other compounds of the series (Figure 10.2).
Design, synthesis and biological evaluation of novel thiazole-naphthalene derivatives as potential anticancer agents and tubulin polymerisation inhibitors
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Guangcheng Wang, Wenjing Liu, Meiyan Fan, Min He, Yongjun Li, Zhiyun Peng
A series of thiazole-naphthalene derivatives (5a–5c and 6a–6n) were synthesised according to the pathways described in Scheme 1. Deoxybenzoins 3a–3c was prepared by condensation of 1-methoxynaphthalene 1 with appropriate phenylacetic acids 2 in the presence of trifluoroacetic anhydride (TFAA) in trifluoroacetic acid (TFA) at room temperature. Treatment of 3a–3c with pyridinium tribromide in CH2Cl2 to give compounds 4a–4c. Then, condensation of 4a–4c with thiourea under reflux in ethanol to afford the title compounds (5a–5c) in high yields. Finally, a series of thiazole-naphthalene derivatives (6a–6n) were prepared by a condensation reaction of 5a–5c with a variety of commercially available acid anhydride. All of the title compounds are new and not reported in the literature to date.
Fluorinated vectors for gene delivery
Published in Expert Opinion on Drug Delivery, 2022
Yu Wan, Yuhan Yang, Mingyu Wu, Shun Feng
Most fluorinated vectors were prepared by grafting fluoroalkyl chains or fluoroaromatic compounds onto well-established polymers by different conjugation reactions. Generally, the cationic polymers have free amino groups, which become the primary conjugation reaction site (Figure 2a). The reaction efficiency of an amino group and fluorine-containing acid anhydride is the highest, and the connection efficiency of the two can reach more than 95% under normal temperature conditions with a 1:1 feeding ratio. The fluorination degree plays a significant role in impacting gene delivery efficiency. Taking the fluoroalkyl chain as an example, if the fluoroalkyl chain is too short, a stable transfection complex cannot be formed through the fluorophilic effect. However, if the fluoroalkyl chain is too long, it will form a shielding effect on the charges on the polymer surface, affecting the electrostatic interaction between the vectors and the nucleic acids [27,28]. Trifluoroacetic anhydride, pentafluoropropionic anhydride, heptafluorobutyric anhydride, and nonafluorobutanesulphonic anhydride have been grafted on the polyamidoamine (PAMAM), respectively, and the transfection efficiency results showed that the heptafluorobutyric acid-grafted dendrimer had the highest plasmid DNA (pDNA) delivery efficiency [28]. Therefore, numerous studies used the heptafluorobutyric anhydride as a fluorination reagent to modify non-viral vectors [29–35]. Besides, the optimized fluorination degree is varied for different nucleic acid molecules, such as generation-5 (G5) PAMAM with a 57.8% grafting rate, that can efficiently transfect DNA. In comparison, only a 64% grafting rate or higher can efficiently deliver siRNA [35]. Thus, the grafting ratio and the number of fluorine atoms are needed to be optimized to achieve the best transfection efficiency.
Synthesis of new pyridothienopyrimidinone and pyridothienotriazolopyrimidine derivatives as pim-1 inhibitors
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2018
Hala B. El-Nassan, Bassem H. Naguib, Engy A. Beshay
A mixture of compound 5 (0.64 g, 0.002 mol) and acetic anhydride or 2,2,2-trifluoroacetic anhydride (4 ml) was heated under reflux for 5 h and then allowed to cool. The reaction mixture was poured onto ice-cold water (100 ml) and the product was filtered, dried and crystallised from acetic acid.