The rapid preparation of 2-aminosulfonamide-1,3,4-oxadiazoles using polymer-supported reagents and microwave heating

I2-Mediated Synthesis of 1,3,4-Oxa/thiadiazoles from Aroylhydrazide and Acetonitrile/Thioacetamide

A facile and convenient metal-free direct oxidative amination of acetonitrile followed by cyclization with aroyl hydrazide for synthesizing oxadiazoles has been investigated. Disubstituted 1,3,4-oxadiazoles were obtained at 50-82% yields using readily available acetonitrile as both reagent and solvent. In addition, the reaction of aroyl hydrazides with thioacetamide and cyanothioacetamide afforded 5-methyl-2-aryl-1,3,4-thiadiazoles and 2-aryl-1,3,4-oxadiazole-2-acetonitriles as the main products, respectively.

Evaluation of developmental toxicity in zebrafish embryos and antiproliferative potential against human tumor cell lines of new derivatives containing 4-nitrophenyl group

The aim of the studies was to evaluate the antiproliferative potential against human tumor cell lines of newly synthetized derivatives containing 4-nitrophenyl group, as well as its impact on developmental toxicity in zebrafish model. We selected 1-(4-nitrobenzoyl)-4-ethylsemicarbazide (APS-1) and 1-[(4-nitrophenyl)acetyl]-4-hexyl-thiosemicarbazide (APS-18) for research. The antiproliferative properties of semicarbazide derivatives were assessed against human cancer cell lines derived from hepatocellular adenocarcinoma (HepG2), renal cell carcinoma (769-P), non-small cell lung cancer (NCI-H1563) and glioblastoma multiforme (LN229) in comparison to the physiological human embryonic kidney (HEK-293) cell line. The influence of the tested substances on the cell cycle and apoptosis was also evaluated. Fish embryo acute toxicity test (FET) was performed based on OECD Guidelines (Test No. 236), and was carried out for the first 5 days post fertilization. The following concentrations of APS-1 and APS-18 were tested: 125-2000 μM and 0.125-1000 μM, respectively. The presented studies on the antiproliferative properties of the new semicarbazide derivatives showed that the compounds APS-1 and APS-18 reduce the viability of human tumor lines. Particularly noteworthy is the strong and selective antiproliferative activity of APS-18 against all neoplastic cell lines, in particular against glioblastoma. Against this tumor line, the compound APS-1 showed an effective inhibitory effect. In the FET we noted that the direct exposure of zebrafish embryos to APS-1 and APS-18 in used range of concentration did not cause morphological abnormalities, including cardiotoxicity. On basis of obtained outcomes it could be concluded that APS-1 and APS-18 may constitute models for further research, design and synthesis of new, safer drugs with more favorable anticancer properties.

Preparation of 1,3,4-oxadiazole derivatives via supported and unsupported phosphinium dibromide reagents

In this work, the synthesis of 1,3,4-oxadiazole derivatives using triphenylphosphine dibromide/triethylamine (Ph3P/Br2/Et3N), 1,2-bis(diphenylphosphaneyl)ethane/2Br2/Et3N, and nano-silica-anchored PPh2/Br2/Et3N systems is described. The method allows the preparation of 1,3,4-oxadiazoles with a broad substrate scope from easily accessible materials.

Lemon Juice as a Biocatalyst Under Ultrasound Irradiation: Synthesis and Pharmacological Evaluation of 2-amino 1,3,4-thiadiazoles

BACKGROUND

The 2-amino 1,3,4-thiadiazole framework has attracted considerable interest because of its prevalence in compounds possessing a wide range of pharmacological properties including anticancer/antitumor activities. Though a number of methods have been reported for the synthesis of this class of compounds, some of them are not straightforward, inexpensive and environmentally friendly.

OBJECTIVE

To synthesize 2-amino-1,3,4-thiadiazole derivatives that could act as potential anticancer agents.

METHODS

The use of lemon juice as an inexpensive and readily available biocatalyst was explored in the synthesis of 2-amino 1,3,4-thiadiazole derivatives. Accordingly, a convenient method has been developed for the rapid synthesis of this class of compounds under a mild and non-hazardous reaction condition in good yields. The methodology involved the reaction of various acid hydrazides with TMSNCS in the presence of lemon juice in PEG-400 at room temperature (25-30ºC) under ultrasound irradiation. These compounds were assessed for their cytotoxic properties against two different metastatic breast cancer cell lines e.g., MDAMB-231 and MCF-7 and subsequently against SIRT1.

RESULTS

The 2-amino 1,3,4-thiadiazole derivatives 3a, 3i, 3j and 3l showed promising growth inhibition of MDAMB- 231 and MCF-7 cell lines and SIRT1 inhibition in vitro. Indeed, 3i was found to be a potent inhibitor of SIRT1.

CONCLUSION

An ultrasound-assisted method facilitated by lemon juice has been developed to synthesize 2-amino- 1,3,4-thiadiazole derivatives that could act as potential anticancer agents.

Synthesis, In Vitro Screening and Docking Studies of New Thiosemicarbazide Derivatives as Antitubercular Agents

A series of thiosemicarbazide derivatives was designed and synthesized by reaction of carboxylic acid hydrazide with isothiocyanates. The molecular structures of the investigated thiosemicarbazides were confirmed and characterized by spectroscopic analysis. The conformational preference of carbonylthiosemicarbazide chain and intra- and intermolecular interactions in the crystalline state were characterized using X-ray analysis. The antituberculosis activity of the target compounds were tested in vitro against four Mycobacterium strains: M. H37Ra, M. phlei, M. smegmatis, M. timereck. The most active compounds were those with 2-pyridine ring. They exhibited lower minimal inhibitory concentration (MIC) values in the range 7.81–31.25 μg/mL in comparison to the other isomers. Compound 5 had activity against M. smegmatis at a concentration of 7.81 μg/mL whereas compound 2 had activity against all tested strains at a concentration of 15.625 μg/mL. The molecular docking studies were performed for investigated compounds using the Mycobacterium tuberculosis glutamine synthetase MtGS as their molecular target.

Current Parallel Solid-Phase Synthesis of Drug-like Oxadiazole and Thiadiazole Derivatives for Combinatorial Chemistry

Solid-phase organic synthesis is a powerful tool in the synthesis of small organic molecules and building of libraries of compounds for drug discovery. Heterocyclic compounds are important components of the drug discovery field as well and serve as a core for hundreds of marketed drugs. In particular, oxadiazole and thiadiazole cores are compounds of great interest due to their comprehensive biological activities and structural features. Therefore, a plethora of oxadiazole and thiadiazole synthesis methodologies have been reported to date, including solution and solid-phase synthesis methodologies. In this review, we concentrate on and summarize solid-phase synthetic approaches of the oxadiazole and thiadiazole derivatives.

Construction of 1,3,4-Oxadiazole and 1,3,4-Thiadiazole Library with a High Level of Skeletal Diversity Based on Branching Diversity-Oriented Synthesis on Solid-Phase Supports

An efficient solid-phase synthetic route for the construction of 1,3,4-oxadiazole and 1,3,4-thiadiazole libraries based on branching diversity-oriented synthesis (DOS) has been developed in this study. The core skeleton resins, 1,3,4-oxadiazole and 1,3,4-thiadiazole, were obtained through desulfurative and dehydrative cyclizations of thiosemicarbazide resin, respectively. Various functional groups have been introduced to the core skeleton resins, such as aryl, amine, amide, urea, thiourea, and an amino acid. Most of the libraries were purified by simple trituration without extraction or column chromatography after cleavage of the products from the solid-supported resin. As a result, we obtained high yields of pure 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives (total numbers = 128). Finally, we confirmed the drug-like properties of our library by calculation of physicochemical properties, displays of the skeletal diversities of the library in 3D-space, and occupation of a broad range of areas by their functional groups.

Facile one-pot synthesis of 2-amino-1,3,4-oxadiazole tethered peptidomimetics by molecular-iodine-mediated cyclodeselenization

Mild and highly efficient I₂ and Et₃N aided cyclodeselenization of in situ generated selenosemicarbazide is described to obtain 2-amino-1,3,4-oxadiazole peptidomimetics.

Solid-Phase Synthesis of 1,3,4-Thiadiazole Derivatives via Desulfurative Cyclization of Thiosemicarbazide Intermediate Resin

A 1,3,4-thiadiazole library was constructed by solid-phase organic synthesis. The key step of this solid-phase synthesis involves the preparation of polymer-bound 2-amido-5-amino-1,3,4-thiadiazole resin by the cyclization of thiosemicarbazide resin using p-TsCl as the desulfurative agent, followed by the functionalization of the resin by alkylation, acylation, alkylation/acylation, and Suzuki coupling reactions. Both the alkylation and acylation reactions chemoselectively occurred at the 2-amide position of 2-amido-5-amino-1,3,4-thiadiazole resin and the 5-amine position of 2-amido-5-amino-1,3,4-thiadiazole resin, respectively. Finally, these functionalized 1,3,4-thiadiazole resins were treated with trifluoroacetic acid in dichloromethane, affording diverse 1,3,4-thiadiazole analogs in high yields and purities. The 1,3,4-thiadiazole analogs show a different distribution of physicochemical and biological properties compared with our previously constructed 1,3,4-oxadiazole and 1,3,4-thiadiazole libraries in a range of orally available drug properties.

Ultrasonics in isocyanide-based multicomponent reactions: a new, efficient and fast method for the synthesis of fully substituted 1,3,4-oxadiazole derivatives under ultrasound irradiation

A fast and convenient approach to the synthesis of fully substituted 1,3,4-oxadiazoles via three-component reaction of aromatic carboxylic acids, acenaphthoquinone, and (N-isocyanimino)triphenylphosphorane under ultrasound irradiation is described. Furthermore, a series of compounds were synthesized and characterized by melting point, IR, NMR and MS. Utilization of easy reaction conditions, very high to excellent yields, and short reaction times makes this manipulation potentially very useful.

Novel, fast and efficient one-pot sonochemical synthesis of 2-aryl-1,3,4-oxadiazoles

Ultrasound promoted synthesis of 2-aryl-1,3,4-oxadiazoles at ambient temperature is reported. The remarkable features of the new procedure are shorter reaction time, excellent yields, cleaner reaction profile and simple experimental and workup procedure.

Regioselective synthesis of 2-amino-substituted 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives via reagent-based cyclization of thiosemicarbazide intermediate

A regioselective, reagent-based method for the cyclization reaction of 2-amino-1,3,4-oxadiazole and 2-amino-1,3,4-thiadiazole core skeletons is described. The thiosemicarbazide intermediate 3 was reacted with EDC·HCl in DMSO or p-TsCl, triethylamine in N-methyl-2-pyrrolidone to give the corresponding 2-amino-1,3,4-oxadiazoles 4 and 2-amino-1,3,4-thiadiazoles 5 through regioselcective cyclization processes. The regioselectivity was affected by both R(1) and R(2) in p-TsCl mediated cyclization. It is shown in select sets of thiosemicarbazide 3 with R(1)(benzyl) and R(2)(phenyl). 2-Amino-1,3,4-oxadiazole 4 was also shown in the reaction of p-TsCl mediated cyclization. The resulting 2-amino-1,3,4-oxadiazole and 2-amino-1,3,4-thiadiazole core skeleton are functionalized with various electrophiles such as alkyl halide, acid halides, and sulfornyl chloride in high yields.