Letters in Organic Chemistry - Volume 17, Issue 6, 2020

Oxadiazole moiety, which is one of the heterocyclic aromatic groups of the azole family; with the molecular formula C2H2N2O, exists in four isomeric form; out of which, 1,2,4-oxadiazole; 1,2,5-oxadiazole and 1,3,4-oxadiazole are common isomers. The stable isomeric forms of oxadiazoles are observed in a variety of pharmaceutical important potent drugs including raltegravir, butalamine, fasiplon, oxolamine and pleconaril. An attempt has been made to emphasize the chemistry and pharmacology associated with oxadiazole and its derivatives. A number of oxadiazole derivatives are very popular and common in use as potential therapeutic agents. However, a number of researchers are working and have worked to find out more synthetic analogues for anticancer and antifungal, anti-HIV agents using biological and in-silico models.

In this review, a survey on the behavior of 2(3H)-furanones as alkylating agents is systematized. It is obvious that the direction of the reaction was mainly dependent on the solvent used. Furanones reacted with AlCl3 in excess benzene, toluene, or anisole to give the corresponding butadienecarboxylic acids via an intermolecular alkylation mode. Carrying out the reaction in tetrachloroethane and nitrobenzene as solvents, the reactions may lead to intramolecular alkylation mode or fail to give any product and the unreacted furanones were isolated, depending upon the electron density on C-2 at the aryl group situated at position-3.

We report the isolation and determination of the essential oil composition from the leaves and rhizomes of Polianthes tuberosa (P. tuberosa), Polianthes sessiliflora (P. sessiliflora) and Polianthes longiflora (P. longiflora) species. These essential oils were extracted using supercritical CO2 extraction method, and their structures were characterised by GC-FID and GC/MS approaches. Methyl 2-aminobenzoate, isoeugenol, 5-octadecene, benzyl benzoate, 1-nonadecene, and diisobutylphthalate were identified as their major chemical compositions. Moreover, the anti-cancer activity of the total essential oils from these three Polianthes species was evaluated against five cancer cell lines.

The elimination of volatile organic solvents in organic synthesis is the most important goal in “Green” chemistry. We report a simple, efficient and facile method for the addition of progargyl bromide to carbonyl compounds using Mg metal as a mediator under solvent-free conditions which could regioselectively generate homopropargyl alcohols efficiently in good to excellent yields. The procedure has advantages such as short reaction time, operationally simple, excellent product yields, high regioselectivity and organic solvent-free.

A group of silica-ionic liquid supported Ru-based catalysts was synthesized and further utilized for CO2 hydrogenation reaction. All the materials were properly analyzed in terms of their physicochemical properties. The physiochemical impacts of different functionalized and non-functionalized ionic liquid over the synthesis, size, and stability of Ru NPs along with their effect on the rate of hydrogenation reaction were investigated. The Ru-[DAMI][NTf2] (1:10)@SiO2 furnished the best catalytic performance in CO2 conversion to formic acid under high-pressure reaction condition. The results confirmed the impact of ionic liquids as a repellent to avoid agglomeration and oxidation of the Ru nanoparticles followed by space resistance and electrostatic protection. Hence, such influence positively begins the rate of reaction as well as the selectivity of the process. Good physiochemical stability of catalyst in terms of 7-time catalyst recycling and easy product/catalyst isolation make this protocol near to the principal of sustainable chemistry.

Eight secondary metabolites (1-8) were isolated from the roots of Vietnamese Eurycoma longifolia. The structures of these compounds were elucidated using a variety of spectroscopic methods. Among the compounds was eurylongilactone A (1), a new oxygenated C20 quassinoid with a 11β,20-epoxy bridge. The anti-inflammatory activities of the compounds were evaluated against LPSinduced NO production in RAW264.7 cells. Compound 1 and ethyl ferulate (8) had the strongest inhibitory effects, with IC50 values of 3.03 ± 0.73 and 3.56 ± 0.43 μM, respectively. Compounds 2, 4, and 7 had moderate activity.

A simple and efficient method was developed for the synthesis of pyrazole derivatives via a one-pot reaction of 1,3-diketone and substituted hydrazines in the presence of nano-SnCl4/SiO2 as a mild catalyst. A series of some pyrazole derivatives (P1-P11) was synthesized and evaluated as antifungal and anti-cancer agents. Compounds P10 and P11 were demonstrated. The antimicrobial activities of the synthetic compounds showed that compounds P10 and P11 most excellently inhibited the growth of dermatophytes or Aspergillus species, respectively. Therefore, the cytotoxic activities of these compounds on two human cancer cell lines, A549 (lung cancer) and MCF-7 (breast cancer) were further assessed. Hence, results demonstrated that beside antifungal activity, P10 had also desirable cytotoxic effect on investigated cancerous cell lines, even higher than cisplatin.

This study aimed at evaluating the antibiofilm activity of the Red Sea metabolites from green alga Avrainvillea amadelpha, sea cucumber Holothuria atra and costal plant Sarcocornia fruticosa against three biofilm bacterial strains isolated from Jeddah coast. Free fatty acids (FFAs) and other lipoidal matters were extracted from these organisms and analyzed by GC-MS. The composition of lipoidal fractions showed that A. amadelpha is rich by 74% saturated FAs, while sea cucumber H. atra revealed high content (60%) of unsaturated FAs. Palmitic acid is the major FA component in all species ranging from 14.5 to 26.7%. Phytol, sterols and hydrocarbons (C8-C29) were represented in the alga A. amadelpha as high contents with values 25.8, 21.9 and 18.5%, respectively. The extracts and lipoidal contents showed biofilm inhibitory activity against the isolated bacterial strains, where the unsaponified lipoidal fraction of S. fruticosa exhibited highest inhibitory activity against Planomicrobium sp. at concentration of 200 μg/mL.

Two pyridinium amide-based receptors L1 and L2 with a small difference of H-bond position of the amide have been synthesized and characterized. Interestingly, they exhibited a huge difference in sensing towards AcO- and H2PO4 -, respectively. Receptor L1 was found to be ‘naked-eye’ selective for AcO- anions, while receptor L2 showed clear fluorescence enhancement selective to H2PO4 - anion. The recognition ability has been established by fluorescence emission, UV-vis spectra, and 1HNMR titration.

Sawdust supported N-heterocyclic carbene-nickel complex has been prepared by covalent grafting of 1-methyl imidazole in the matrix of chloropropyl modified sawdust followed by reaction with nickel acetate. The resultant NHC-Ni complex was employed as a heterogeneous catalyst for the synthesis of 2-substituted benzoxazoles from benzoxazole and aryl boronic acids following C-H activation strategy. The recycling experiments showed that the complex could be reused for five consecutive runs without significant loss in the yield of products.