Design,Synthesis, and Cytotoxicity of Semisynthetic Betulinic Acid-1,2,4-Oxadiazole Amide Derivatives

Biological activity of betulinic acid derivatives containing a 1,2,4-oxadiazole ring prompted us to synthesize betulinic acid-1,2,4-oxadiazole amide derivatives 14–25 starting with the amide coupling reaction of betulinic acid 1 and (3-aryl-1,2,4-oxadiazol-5-yl)methanamines 2–13. The products were tested for cytotoxicity on three human cancer cell lines in vitro. All tested compounds demonstrated high activity. The structures of the synthesized compounds were elucidated from IR, NMR and mass spectra.     

Synthesis and biological evaluation of 5,6,7-trimethoxy- 1- benzylidene-3,4-dihydro-naphthalen-2-one as tubulinpolymerization inhibitors

A series of new combretastatin-A4 analogs were synthesized, in which a six-membered ring connects the linking bridge and A ring, and their tumor cell growth and tubulin-polymerization inhibitory activity were evaluated. These compounds appear to be potential tubulin-polymerization inhibitors. Compounds 1b with amino substituted on position 3 of B ring conferred optimal bioactivity, higher than that of the lead compound 22b and equivalent to that of CA-4. The binding modes of these compounds to tubulin were obtained by molecular docking, which can explain the structure-activity relationship. The studies presented here provide a new structural type for the development of novel antitumor agents.     

Design,synthesis and anti-proliferative effects in tumor cells of new combretastatin A-4 analogs

A total of 11 novel combretastatin A-4(CA-4) analogs were designed, synthesized, and evaluated for the anti-proliferative effects in tumor cells. The compounds represent four structural classes:(i)hydrogenated derivatives,(ii) ethoxyl derivatives,(iii) amino derivatives and(iv) pro-drugs. Biological evaluations demonstrate that multiple structural features control the biological potency. Three of the compounds, sit-1, sit-2 and sit-3, have potent anti-proliferative activity against multiple cancer cell lines. Their pro-drugs were synthesized to increase water solubility. Structure–activity relationship study and Surflex-Docking were studied in this paper. These results will be useful for the design of new CA-4 analogs that are structurally related to the SAR study.     

6-硝基苯并咪唑杂环衍生物的合成

以６－硝基苯并咪唑－１－乙酰肼和５－（６－硝基苯并咪唑－１－亚甲基）－３－巯基－４－氨基－１,２,４－三唑为原料,在不同条件下合成了一系列新的均三唑〔３,４－ｂ〕－１,３,４－噻二唑,１,２,４－三唑和１,３,４－恶二唑衍生物。化合物的结构均经元素分析、＾１Ｈ ＮＭＲ、ＩＲ和ＭＳ确证,并对其波谱性质进行了讨论。     

An efficient synthesis of new thiazolidin-4-one fused s-triazines as potential antimicrobial and anticancer agents

As a part of our endeavor toward the synthesis of new heterocyclic bioactive agents, two series of thiazolidin-4-one fused s-triazines were synthesized by applying an efficient palladium catalyzed C–C Suzuki coupling using catalyst system Pd(OAC)₂, Xphos and K₃PO₄ as a base in toluene solvent. Moreover, the synthesized analogs were further screened for their in vitro antimicrobial as well as anticancer efficacy against prostate cancer PC3 cells. Some compounds displayed remarkable antimicrobial activity and noticeable anticancer activity. It was observed that, both benzonitrile and nicotinonitrile are essential to increase the different pharmacological activities. The newly synthesized compounds were characterized by IR, 1H NMR, 13C NMR and MS analysis.     

5-Nitrotetrazol and 1,2,4-Oxadiazole Methylene-Bridged Energetic Compounds: Synthesis,Crystal Structures and Performances

A new structural type for melt cast materials was designed by linking nitrotetrazole ring with 1,2,4-oxadiazole through a N-CH₂-C bridge for the first time. Three N-CH₂-C linkage bridged energetic compounds, including 3-((5-nitro-2H-tetrazol-2-yl) methyl)-1,2,4-oxadiazole (NTOM), 3-((5-nitro-2H-tetrazol-2-yl)methyl)-5-(trifluoromethyl)-1,2,4 -oxadiazole (NTOF) and 3-((5-nitro-2H-tetrazol-2-yl)methyl)-5-amine-1,2,4-oxadiazole (NTOA), were designed and synthesized through a two-step reaction by using 2-(5-nitro-2H-tetrazole -2-yl)acetonitrile as the starting material. The synthesized compounds were fully characterized by NMR (¹H, ¹³C), IR spectroscopy and elemental analysis. The single crystals of NTOM, NTOF and NTOA were successfully obtained and investigated by single-crystal X-ray diffraction. The thermal stabilities of these compounds were evaluated by DSC-TG measurements, and their apparent activation energies were calculated by Kissinger and Ozawa methods. The crystal densities of the three compounds were between 1.66 g/cm³ (NTOA) and 1.87 g/cm³ (NTOF). The impact and friction sensitivities were measured by standard BAM fall-hammer techniques, and their detonation performances were computed using the EXPLO 5 (v. 6.04) program. The detonation velocities of the three compounds are between 7271 m/s (NTOF) and 7909 m/s (NTOM). The impact sensitivities are >40 J, and the friction sensitivities are >360 N. NTOM, NTOF and NTOA are thermally stable, with decomposition points > 240 °C. The melting points of NTOM and NTOF are 82.6 °C and 71.7 °C, respectively. Hence, they possess potential to be used as melt cast materials with good thermal stabilities and better detonation performances than TNT.     

Synthesis and characterization of new mesogenic esters derived from 1,2,4-oxadiazole and study the effect of alkoxy chain length in their liquid crystalline properties

In this study, a new series of non-symmetrically 3,5-disubstituted of 1,2,4-oxadiazole derivatives, 4-[5-(4-methylphenyl)-1,2,4-oxadiazol-3-yl]-phenyl-4-alkoxybenzoate (G₁–G₁₁), which containing ether and ester linkages in the same molecule, is synthesized using different synthetic procedures and their structures are confirmed by several spectroscopic techniques (FT-IR and ¹H nuclear magnetic resonance). The mesomorphic properties of these compounds are studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM); all these derivatives exhibited as mesogens and displayed an enantiotropic liquid crystal with nematic texture, the nematogenic phase of these materials was appeared in wide temperature ranges on heating and cooling cycles that were observed by POM and DSC. The influence of 1,2,4-oxadiazole ring and the elongation of alkyl chain in the mesomorphic properties of this series were investigated. The mesogenic behaviour of this series was compared with the compounds possessing a somewhat similar structure.     

Synthesis of various 3-substituted 1,2,4-oxadiazole-containing chiral beta 3- and alpha-amino acids from Fmoc-protected aspartic acid

Various 3-substituted chiral 1,2,4-oxadiazole-containing Fmoc-beta(3)- and -alpha-amino acids were synthesized from Fmoc-(l or d)-Asp(OtBu)-OH and Fmoc-l-Asp-OtBu, respectively, in three steps (i.e., condensation of an aspartyl derivative with differentially substituted amidoximes, formation of the 1,2,4-oxadiazole, and cleavage of the tert-butyl ester). These compounds represent new series of nonnatural amino acids, which could be used in combinatorial synthesis. A simple protocol has been developed to generate the 1,2,4-oxadiazole ring. Indeed, common methods resulted in cleavage of the Fmoc group or required long reaction times. We found that sodium acetate in refluxing ethanol/water (86 degrees C) was a convenient and efficient catalyst to promote conversion of Fmoc-amino acyl amidoximes to 1,2,4-oxadiazoles, and this procedure proved to be compatible with Fmoc protection. It is shown that these compounds can be prepared without significant loss of enantiomerical purity. Furthermore, the alkaline conditions used to cleave the Fmoc protecting group from these compounds did not induce epimerization of their chiral center.     

Polyalkoxybenzenes from plant raw materials 4. Parsley and dill seed extracts in the synthesis of polyalkoxy-3,5-diaryl-1,2,4-oxadiazoles with antiproliferative activity

Polyalkoxy-5-(4-hydroxyphenyl)-3-phenyl-1,2,4-oxadiazoles were prepared from allylpolyalkoxybenzenes, the main metabolites of parsley and dill seeds. Due to the spatial arrangement of the aryl substituents provided by 1,2,4-oxadiozole fragment, these compounds can be considered as structural analogs of natural antimitotic combretastatins. The antimitotic activity of the synthesized compounds was evaluated in vivo using sea urchin embryo test.     

Novel 3-Acetyl-2,5-disubstituted-1,3,4-oxadiazolines: Synthesis and Biological Activity

The aim of our study was the two-stage synthesis of 1,3,4-oxadiazole derivatives. The first step was the synthesis of hydrazide–hydrazones from 3-methyl-4-nitrobenzhydrazide and the corresponding substituted aromatic aldehydes. Then, the synthesized hydrazide–hydrazones were cyclized with acetic anhydride to obtain new 3-acetyl-2,3-disubstituted-1,3,4-oxadiazolines. All of obtained compounds were tested in in vitro assays to establish their potential antimicrobial activity and cytotoxicity. Our results indicated that few of the newly synthesized compounds had some antimicrobial activity, mainly compounds 20 and 37 towards all used reference bacterial strains (except Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa) and fungi. These substances showed a strong or powerful bactericidal effect, especially against Staphylococcus spp. belonging to Gram-positive bacteria. Compound 37 was active against Staphylococcus epidermidis at minimal inhibitory concentration (MIC) = 0.48 µg/mL and was characterized by low cytotoxicity. This compound possessed quinolin-4-yl substituent in the second position of 1,3,4-oxadiazole ring and 3-methyl-4-nitrophenyl in position 5. High effectiveness and safety of these derivatives make them promising candidates as antimicrobial agents. Whereas the compound 20 with the 5-iodofurane substituent in position 2 of the 1,3,4-oxadiazole ring showed the greatest activity against S. epidermidis at MIC = 1.95 µg/mL.     

3-(4-R-3-Furazanyl)-5-nitropyrazolyl-1,2,4-oxadiazoles as a new class of energy rich ensembles

A number of new energetic compounds were synthesized based on a combination of pyrazole, furazan, and 1,2,4-oxadiazole. Density, temperature of decomposition, and mechanical sensitivity of the compounds obtained were experimentally determined. Their detonation parameters were calculated.

     

Tautomerism of aza cycles: II. Synthesis and structure of 5-substituted 3-(2-hydroxyethylsulfanyl)-1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazoles and their salts. Preference of the 1H,4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazolium tautomers

New complexing agents, potentially tautomeric 3-(2-hydroxyethylsulfanyl)-1H-1,2,4-triazole, its 5-methyl-and 5-phenyl-substituted analogs, and some their salts, were synthesized, and their structure was discussed on the basis of the ¹H and ¹³C NMR, IR, and mass spectra, X-ray diffraction data, and published data. In keeping with the rule formulated previously for N-unsubstituted 1,2,4-triazoles having dissimilar substituents, the synthesized compounds were found to exist as 3-(2-hydroxyethylsulfanyl)-5-R-1H-1,2,4-triazole tautomers (3-R_A-5-R_D-1H-1,2,4-triazoly). They are protonated at the nitrogen atom in position 4 of the triazole ring. The ¹H and ¹³C NMR spectra of these compounds in trifluoroacetic acid suggest the presence of two forms due to equilibrium between the neutral and protonated species. Analysis of the crystallographic data for the triazolium salts and published data showed preference of the 1H,4H-1,2,4-triazolium tautomer.     

1,2,4-Oxadiazole ring–containing pyridylpyrazole-4-carboxamides: Synthesis and evaluation as novel insecticides of the anthranilic diamide family

Herein, we describe the preparation of pyridylpyrazole-4-carboxamides containing a 1,2,4-oxadiazole ring as novel anthranilic diamide derivatives and compare their insecticidal activities to that of chlorantraniliprole, a well-established potent insecticide. Biological activity tests reveal that all compounds had good insecticidal activities, with the most potent species achieving diamondback moth (Plutella xylostella) mortalities of 100% and 57% at concentrations of 400 and 200 μg mL⁻¹, respectively.     

Synthesis of 5,7-Dimethyl-2-(5-Substituted-1,3,4-Oxadiazole-2-yl)- Methylenethio-1,2,4-Triazolo[1,5-a]Pyrimidines as Potential Fungicides

New challenging problems in plant protection technology have promoted research to discover more efficient pesticides. In recent years, many chemists have paid much attention to compounds bearing 1,2,4-triazolo [1,5-a] pyrimidine rings due to their broad spectrum of biological activities such as herbicidal and fungicidal effects1-7. Up to now, a great variety of these kinds of compounds have been synthesized, among which some commercially herbicides have been developed including metosulam, f…     

Derivatives of 4-amino-4H-1,2,4-triazole-3-thiols linked to the pyrrole cycle and some products of their S-alkylation

This study offers an access to 21 new heterocyclic compounds representing pyrrole derivatives of 4-amino-4H-1,2,4-triazole-3-thiols or 1,3,4-oxadiazole-2-thiols. The principal synthetic approach is based on the cyclization of substituted potassium 2-(pyrrolecarbonyl)hydrazine-1-carbodithionate with hydrazine hydrate to 5-(substituted pyrrolyl)-4-amino-4H-1,2,4-triazole-3-thiols, followed by S-alkylation with methyl iodide or benzyl chloride. Among the resulted thirteen S-alkyl derivatives, five 1,3,4-oxadiazole derivatives have been isolated as secondary products and their formation is explained as being the result of S-alkylation of intermediate 1,3,4-oxa-diazole-2-thiols, generated in the alkaline medium. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 383–391, March, 2007.     

Absorption and luminescence spectra of 5-aryl-3-methyl-1,2,4-oxadiazoles and their chelate complexes with Zinc(II) and copper(II)

5-(2-Hydroxyphenyl)-3-methyl-1,2,4-oxadiazole and its O-methyl and O-acyl derivatives, as well as zinc(II) and copper(II) chelates, were synthesized. All these compounds showed luminescence with the emission maxima ranging from λ = 332 to 490 nm, but only 5-(2-methoxyphenyl)- and 5-(2-acetoxyphenyl)-3-methyl-1,2,4-oxadiazoles and zinc(II) complex of 5-(2-hydroxyphenyl)-3-methyl-1,2,4-oxadiazole were characterized by high luminescence quantum yield (φ = 0.308–0.452, 0.089–0.153, and 0.115–0.334, respectively). Stable conformers of 5-(2-hydroxyphenyl)-3-methyl-1,2,4-oxadiazole with different structures of the coordination entity were identified by DFT quantum chemical calculations.     

Design,Synthesis and Anticancer Activity of 1,2,4-Thiadiazole Derivatives Bearing 1,2,4-Oxadiazole

Russian Journal of General Chemistry - A series of novel 1,2,4-thiadiazole derivatives bearing 1,2,4-oxadiazole is synthesized. Structures of the synthesized compounds are confirmed by 1H and 13C...     

A chemoselective hydroxymethylation: new route for the synthesis of 6-aroyl-4-(4H-triazol-3-yl)thiomorpholin-3-ones

Treatment of 2-(2-oxo-2-arylethylthio)-N-(4H-1,2,4-triazol-3-yl)acetamides with paraformaldehyde in the presence of a base has led to a tandem chemoselective hydroxymethylation followed by cyclization yielding a set of novel 6-aroyl-4-(4H-triazol-3-yl)thiomorpholin-3-ones. The thiomorpholine ring has been found to have a boat like conformation in these compounds as evidenced by NOESY NMR spectrum.     

MNDO calculations applied to structural changes in 1,2,4-oxadiazole substituents

MNDO calculations on several substituted 1,2,4-oxadiazole compounds are discussed. Changes in geometry, atomic charge distribution, rotational barriers and molecular orbital energies are examined. A correlation exists between the thermal stability of the heterocycle and the excess electronic charge accumulated inside the ring as well as its distribution. For the case of phenylated derivatives, the nonplanar conformation is energetically more stable than the corresponding planar one, which might explain the relative decrease in thermal stability of phenylated derivatives. It is observed that as the planar conformation starts being populated, a greater amount of electrons are donated to the 1,2, 4-oxadiazole ring.     

Synthesis and biological evaluation of 1,2,4-oxadiazole linked 1,3,4-oxadiazole derivatives as tubulin binding agents

As an aspect of our ongoing research in search of new anticancer agents, a series of novel analogs of 1,3,4-oxadiazole embedded with 1,2,4-oxadiazole moieties (11a–j) were synthesized. The structure of the final compounds was confirmed by ¹H NMR, ¹³CNMR and mass spectroscopic techniques and evaluated for their in vitro anticancer activity against three human cancer cell lines (lung, breast). Among the synthesized compounds, 11?b, 11?g, 11?h, and 11i showed potent anticancer activity with IC₅₀ values within the range of 0.34?±?0.025 to 2.45?±?0.23?μM against three human cancer cell lines. Further, these compounds (11a–j) were investigated for molecular docking studies. Among them, compound 11?h showed strong binding affinity on binding sites of target protein EGFR (PDB ID: 4hjo) with highest docking score (-7.028). It revealed that 11?h was a strong tubulin binding agent.