Synthesis of New Deoxycholic Acid bis Thiocarbazones under Solvent-Free Conditions using Microwave Irradiation

A color reaction for the determination of Cu2+ in distilled beverages employing digital imaging

In this work, we describe for the first time the synthesis of a thiocarbazone for the selective determination of Cu²⁺ in distilled beverages. The method was based on the complexation reaction of Cu²⁺ with the thiocarbazone, and the colored product was analyzed using a smartphone application. The thiocarbazone reacts with Cu²⁺ to form a 1:1 (metal:ligand) complex. The Cu²⁺ complex was characterized by UV, IR and NMR spectral analyses. The proposed reaction yields a yellow color, and therefore, channel B of the RGB system was used in the analysis. After optimizing the reaction conditions, an analytical curve was obtained to determine Cu²⁺ concentrations ranging between 0.25 and 6.75 mg L^-1; the use of 400 μL sample volumes led to a relative standard deviation (n = 5) of 3.2% and a detection limit of 0.18 mg L^-1. Recovery experiments were performed with sugar cane spirits, whiskies and tequilas to evaluate the accuracy of the method, and the recovery obtained ranged from 80.5 to 112.2%.

Microwave-assisted synthesis of a novel steroid-derived Schiff base chemosensor for detection of Al3+ in aqueous media

A novel steroid-derived Schiff base chemosensor, N′-(2-hydroxybenzylidene)-3α-hydroxy-cholanhydrazide (LA), has been designed and prepared via microwave irradiation. The sensor LA showed highly selective fluorescent sensing for Al3+ with a low detection limit of 34 nM in the pH range from 6.05 to 9.32 in ethanol/water (1:2, v/v) solution. The binding stoichiometry between LA and Al3+ was determined as 1:1 by Job’s plot and further verified with 1H NMR studies. Under a UV lamp, the fluorescence color changes could be easily detected by the naked eye. In addition, the sensor LA has been applied in detection of Al3+ in real water samples.

Microwave-Assisted Synthesis of Bile Acids Derivatives: An Overview

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The first attempts at microwave-assisted (MW) syntheses of bile acid derivatives were performed in domestic MW appliances. However, the reproducibility of these syntheses, which were performed in uncontrolled conditions, was very low. In the first part of this overview, compounds synthesized under such conditions are presented. Consequently, with the development of MW technology, MW-assisted reactions in MW reactors became reproducible. Thus, in the second part of this review, syntheses of bile acidsbased compounds in MW reactors are presented. Among others, publications dealing with the following topics will be covered:

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− Chemical transformations of hydroxyl and/or carboxyl functions of bile acids into esters or amides,

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− Hydroxyl group oxidations,

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− Derivatization of oxo-compounds with different nitrogen-containing compounds (e.g. 4-amino-3- substituted-1H-1,2,4-triazole-5-thiones, thiocarbohydrazides and thiosemicarbazides)

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Bile acid-based molecular tweezers, capable of stereospecific molecular recognition

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Reactions of hydroxyl functions to give chlorine derivatives, presenting reactive intermediates in substitution reactions with N- or O-containing nucleophilic arylhydrazides, urea derivatives, substituted thiadiazoles or triazoles or amino acid methyl esters, mainly in solvent-free conditions.

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Some of the synthesized compounds expressed antimicrobial potential and/or good recognition properties as artificial receptors for specific amino acids or anions.

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Detailed comparisons between conventional and MW-assisted procedures for chemical transformations of bile acids are given in most of the presented publications. Based on these results, MW irradiation methods are simpler, more efficient, cleaner and faster than conventional synthetic methods, meeting the requirements of green chemistry.

Synthesis and evaluation of antitumor, anti-inflammatory and analgesic activity of novel deoxycholic acid derivatives bearing aryl- or hetarylsulfanyl moieties at the C-3 position

Novel deoxycholic acid (DCA) derivatives were stereoselectively synthesised with -OH and -CH₂SR moieties at the C-3 position, where R was a substituted aryl [2-aminophenyl (8) or 4-chlorophenyl (9)] or hetaryl [1-methylimidazolyl (5), 1,2,4-triazolyl (6), 5-amino-1,3,4-thiadiazolyl (7), pyridinyl (10) or pyrimidinyl (11)]. These compounds were prepared in good yields from the C-3β-epoxy derivative 2 in the epoxide ring-opening reaction by S-nucleophiles. These derivatives were evaluated for their in vitro anti-proliferation activity in a panel of tumor cell lines. Data showed that: (i) heterocycle-containing derivatives displayed higher cytotoxicity profiles than the parent molecule; (ii) heterocyclic substituents were more preferable than aryl moieties for enhancing anti-proliferation activity; (iii) the sensitivity of tumor cell lines to analysed compounds decreased in the following order: HuTu-80 (duodenal carcinoma)>KB-3-1 (cervical carcinoma)>HepG2 (hepatocellular carcinoma)>MH-22a (hepatoma); (iv) compounds 5, 6 and 11 exhibited a high cytotoxic selectivity index (HuTu-80: SI>7.7, 38.5 and 12.0, respectively). Compounds 2 and 6-8 markedly inhibited NO synthesis by interferon γ-induced macrophages. Screening for anti-inflammatory activity of these derivatives in vivo showed their high potency on histamine- (5, 10) and formalin- (2, 10, 11) induced paw edema models.

Microwave-Assisted Synthesis and Antibacterial Activity of Methyl 1-{2-[4-Amino-5-(Naphthalen-1-yl)-4H-1,2,4-Triazol-3-Ylthio]ethyl}-1H-Indole-3-Carboxylate Derivatives

Twelve new Schiff bases containing a disubstituted 1,2,4-triazole and a monosubstituted indole linked by a thioethyl group were efficiently synthesised via a method employing microwave irradiation. Compared with a conventional method of heating at 100 °C, yields were increased from 46–48 to 82–92% and the reaction times were reduced from 20–25 h to 4–7 min. The structures of these novel hexacyclic Schiff bases were characterised by their spectral data and elemental analysis. Evaluation of their antibacterial activity showed that many of them possess excellent activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis.

Microwave-Assisted Synthesis and Antibacterial Activity of Unsymmetrical Indolyl/Aryl Bis-Thiosemicarbazones

A series of nine novel unsymmetrical bis-thiosemicarbazones were prepared in high yield by condensation of aromatic aldehyde thiosemicarbazones with indole-3-carboxaldehyde using microwave irradiation. The structures of the new compounds were characterised. Six of the compounds displayed varying levels of antibacterial activity against Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus.

An Efficient Synthesis of Novel Bis-1,3,4-Thiadiazolyl-Carbamate Derivatives based on Deoxycholic Acid under Microwave Irradiation

An easy and efficient method for the synthesis of novel deoxycholic acid bis-1,3,4-thiadiazol-carbamate derivatives under microwave irradiation has been developed. Twelve new methyl 3α,12α-bis-[(5-aryl-1,3,4-thiadiazol-2-yl) carbamoyloxy]-cholan-24-oates were obtained in better yield (78–91%) and shorter time (15–22 min). Their structures were identified by 1H NMR, IR, MS spectra and elemental analyses.