STUDY ON THE MECHANISM OF FLUORESCENCE QUENCHING OF NITROCOMPOUNDS FOR OXAZOLES *

The mechanism of nitrocompounds quenching of the fluorescence of 5, 5′ dipheny1 2, 2′ bisoxazole (POOP) and trans 1, 2 bis [2 (5 phenyloxazolyl)] ethene (POEOP) has been studied. It was found that the fluorescence of oxazoles was quenched mainly by the absorption competition and radiationless energy transfer of nitrocompounds. The fluorescence quenching rate constants of nitrobenzene and nitromethane are 3.0×10 10 L·mol -1 ·s -1 and 1.5×10 8 L·mol -1 ·s -1 respectively for POEOP. This remarkable difference was explicated.

One-pot Synthesis of 2,5-Disubstituted Oxazoles Using Poly[styrene(iodosodiacetate)]

Disubstituted oxazoles were prepared conveniently by treatment of aromatic -methyl ketones and nitriles with poly[styrene(iodosodiacetate)] in one-pot process.

Theoretical design of new bridge-ring insensitive high energy compounds by selected normal Diels-Alder reactions between NH_(2)-substituted oxazoles and NO_(2)/NF_(2)/NHNO_(2)-substituted ethylenes/acetylenes

In this work,NH_(2)-substituted oxazoles and NO_(2)/NF_(2)/NHNO_(2)-substituted ethylenes/acetylenes were designed and used as dienes and dienophiles,respectively,in order to develop new bridge-ring insensitive high energy compounds through the Diels-Alder reaction between them.The reaction type,reaction feasibility and performance of reaction products were investigated in detail theoretically.The results showed that dienes most possibly react with dienophiles through the HOMO-diene controlled normal Diels-Alder reaction at relatively low energy barrier.Tetranitroethylene could react with the designed dienes much more easily than other dienophiles,and was employed to further design 29 new bridge-ring energetic compounds.Due to high heat of formation,density and oxygen balance,all designed bridge-ring energetic compounds have outstanding detonation performance,16 of them have higher energy than HMX(1,3,5,7-tetranitro-1,3,5,7-tetrazocine)and 2 others even possess comparative energy with the representative of high energy compounds CL-20(2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane).The predicted average h50 value of these bridge-ring energetic compounds is 83 cm,showing their low impact sensitivity.The NH2 groups could obviously impel the proceeding of Diels-Alder reactions,but would slightly decrease the energy and sensitivity performance.In all,the new designed bridge-ring compounds have both high energy and low sensitivity,and may be produced through Diels-Alder reactions at relatively low energy barrier.This paper may be helpful for the theoretical design and experiment synthesis of new advanced insensitive high energy compounds.

Electrochemical construction of 2,5-diaryloxazoles via N–H and C(sp_(3))-H functionalization

An efficient N–H and C(sp~3)-H functionalization of aryl ketones with benzylamines/amino acids was developed under mild conditions by virtue of anodic oxidation. A variety of functionalized 2,5-diaryloxazoles were obtained with good to excellent yields. Moreover, some important natural products can be prepared by this method. The reaction features a broad substrate scope, scalability, metal-free and chemical oxidant-free.

Rh-Catalyzed Formal[3+2]Cyclization for the Synthesis of 5-Aryl-2-(quinolin-2-yl)oxazoles and Its Applications in Metal lons Probes

Main observation and conclusion A facile and efficient strategy for the synthesis of 5-aryl-2-(quinolin-2-yl)oxazoles via rhodium-catalyzed formal[3+2]cyclization of 4-aryl-1-tosyl-1H-1,2,3-triazoles with quinoline-2-carbaldehydes has been described.The protocol employs mild conditions and offers good yields of diverse 2,5-aryloxazole derivatives with a broad reaction scope.It is amenable to gram-scale synthesis and easily transformation.Moreover,this 5-aryl-2-(quinolin-2-yl)oxazole skeleton is indeed a new fluorophore and its applications in metal ions probes are also investigated and showed fluorescent responses to mercury ion.

A Facile One-pot Synthesis of 2,5-Disubstituted Oxazoles Us-ing Poly[styrene(iodosodiacetate)]

Disubstituted oxazoles were prepared conveniently by treatment of aromatic -methyl ketones and nitriles with poly[styrene(iodosodiacetate)] in a one-pot manner.

Gold-catalyzed oxazoles synthesis and their relevant antiproliferative activities

Nine 5-aryl-2-methyloxazole derivatives were synthesized via gold-catalyzed alkyne oxidation. All of the compounds have been screened for their antiproliferative activities against MCF-7 cell （human breast carcinoma）, A549 cell （human lung carcinoma） and Hela cell （human cervical carcinoma） lines in vitro. The results revealed that compounds 1b, 1c and 1d exhibited strong inhibitory activities against the MCF-7 cell lines （with ICso values of 4.6, 9.7 and 2.2 μmol/L, respectively）.

Iron-Promoted Practical One-Pot Synthesis of 2,5-Disubstituted Oxazoles

A practical one-pot protocol for the synthesis of 2,5-disubstituted oxazoles from 1-aryl-2-nitroethanones was reported. In the presence of iron/AcOH in acetonitrile, the reaction of 1-aryl-2-nitroethanones with trimethyl orthoacetate or trimethyl orthobenzoate delivered the corresponding 2,5-disubstituted oxazoles in moderate to good yields.

Facile Synthesis of 5-Trifluoromethyl-2,4-disubstituted Oxazoles via a Copper（Ⅱ）-Catalyzed and TBHP/I2- Mediated Tandem Oxidative Cyclization

In the presence of Cu（OAc）2·H2O, a variety of 5-trifluoromethyl-2,4-disubstituted oxazoles were easily synthesized via t-BuOOH （TBHP）/I2-mediated tandem oxidative cyclization from readily available starting materials aryl methanamines and α-trifluoroacetyl-substituted ketones or esters under mild conditions, The mechanism was proposed.

Changes of NF-kB,p53,Bcl-2 and caspase in apoptosis induced by JTE-522 in human gastric adenocarcinoma cell line AGS cells:role of reactive oxygen species

AIM: To identify whether JTE-522 can induce apoptosis in AGS cells and ROS also involved in the process, and to investigate the changes in NF-kB, p53, bcl-2 and caspase in the apoptosis process. METHODS: Cell culture, MTT, Electromicroscopy, agarose gel electrophoresis, lucigenin, Western blot and electrophoretic mobility shift assay (EMSA) analysis were employed to investigate the effect of JTE-522 on cell proliferation and apoptosis in AGS cells and related molecular mechanisms. RESULTS: JTE-522 inhibited the growth of AGS cells and induced the apoptosis. Lucigenin assay showed the generation of ROS in cells under incubation with JTE-522. The increased ROS generation might contribute to the induction of AGS cells to apoptosis. EMSA and Western blot revealed that NF-kB activity was almost completely inhibited by preventing the degradation of IkBalpha. Additionally, by using Western blot we confirmed that the level of bcl-2 was decreased, whereas p53 showed a great increase following JTE-522 treatment. Their changes were in a dose-dependent manner. CONCLUSION: These findings suggest that reactive oxygen species, NF-kB, p53, bcl-2 and caspase-3 may play an important role in the induction of apoptosis in AGS cells after treatment with JTE-522.

JTE-522-induced apoptosis in human gastric adenocarinoma cell line AGS cells by caspase activation accompanying cytochrome C release,membrane translocation of Bax and loss of mitochondrial membrane potential

AIM: To investigate the role of the mitochondrial pathway in JTE-522-induced apoptosis and to investigate the relationship between cytochrome C release, caspase activity and loss of mitochondrial membrane potential (Deltapsim). METHODS: Cell culture, cell counting, ELISA assay, TUNEL, flow cytometry, Western blot and fluorometric assay were employed to investigate the effect of JTE-522 on cell proliferation and apoptosis in AGS cells and related molecular mechanism. RESULTS: JTE-522 inhibited the growth of AGS cells and induced the apoptosis. Caspases 8 and 9 were activated during apoptosis as judged by the appearance of cleavage products from procaspase and the caspase activities to cleave specific fluorogenic substrates. To elucidate whether the activation of caspases 8 and 9 was required for the apoptosis induction, we examined the effect of caspase-specific inhibitors on apoptosis. The results showed that caspase inhibitors significantly inhibited the apoptosis induced by JTE-522. In addition, the membrane translocation of Bax and cytosolic release of cytochrome C accompanying with the decrease of the uptake of Rhodamin 123, were detected at an early stage of apoptosis. Furthermore, Bax translocation, cytochrome C release, and caspase 9 activation were blocked by Z-VAD.fmk and Z-IETD-CHO. CONCLUSION: The present data indicate a crucial association between activation of caspases 8, 9, cytochrome C release, membrane translocation of Bax, loss of Deltapsim and JTE-522-induced apoptosis in AGS cells.

Formation of Benzyl Oxazole, A Competitive Path with the Classical Bishler-Napieralski Reaction

Several aromatic ring-substituted N-acetyl-phenylalanine methyl esters were treated with POCl3 in refluxing benzene, which is the typical condition of B-N reaction. It was found that the normal B-N product 3, 4-dihydroisoquinoline-3-carboxylic acid methyl ester and/or 5-benzyl-2-methyl-4-methoxy oxazole could be obtained. The result depended mainly upon the electron-donating property of the substitutes on the benzene ring. Strong electron-donating groups located at para- or ortho- to the cyclization site will facilitate the formation of the normal B-N product 2. On the other hand, the absence or weak electron-donating groups tended to yield the oxazole product 3. It was established that the formation of benzyl oxazole is the competitive path with the B-N reaction. In this article, an explanation was given based on the mechanism of Bishler-Napieralski reaction.

A Case of Abnormal Bishler-Napieralski Cyclization Reaction,Leading to Form Benzyl Oxazole Derivatives

A benzyl oxazole compound 3 was obtained with an excellent yield of 90% when N-acetyl-(2'-methoxy-4',5'-methylenedioxy)-phenylalanine methyl ester 1 was refluxed in POCl1/benzene. However, the anticipated product 3,4-dihydrosioquinoline-3-carboxylic acid methyl ester 2 could not be found. The mechanism was discussed in this article.

Synthesis and bioactivity of novel pyrazole oxime derivatives containing oxazole ring

A series of novel pyrazole oxime derivatives containing oxazole ring were designed and synthesized. The title compounds were structurally confirmed by 1H NMR, 13C NMR spectra and elemental analyses. Preliminary bioassay results showed that some of the title compounds displayed promising fungicidal activity besides insecticidal and acaricidal activity. Particularly, compound 8c exhibited potent fungicidal activity against cucumber Pseudoperonospora cubensis beyond good insecticidal activity against Aphis craccivora and Nilaparvata lugens.

Two novel 2,5-diphenyl oxazole derivatives from Gymnotheca chinensis

Two novel 2,5-diphenyl oxazole derivatives,named gymnothecaoxazoles A（1） and B（2）,were isolated from the whole parts of endemic medicinal plant of Gymnotheca chinensis（Saururaceae）.The structures of the new compounds were elucidated by extensive NMR and MS data,and the structure of compound 1was further confirmed by X-ray crystal diffraction analysis.

In Situ Generation of Oxazole Ylide and Interception with Sulfonamide： Construction of Amidines Using Two Diazo Molecules

A novel generation of oxazole vlide and interception with sulfonamide have been well developed to construct fully substituted amidines. This copper-catalyzed four-component reaction incorporates two diazo molecules to target amidines and shows broad substrate scope, excellent functional groups tolerance and good to excellent yields.

Microwave Assistant Synthesis and Crystal Structures of Two Substituted Oxazole Isoxazole Carboxamides

Two novel substituted phenyl oxazole isoxazole carboxamides have been synthesized by microwave assistant technology.The target compounds were characterized by IR,1H NMR,13C NMR and HRMS,and their single-crystal structures were further determined by X-ray diffraction.3-Phenyl-4-(2΄-methyl-2΄-isopropyl-1΄,3΄-oxazole)-5-methyl isoxazole carboxamide(6a)crystallizes in monoclinic system,space group P21/c with a=6.2137(12),b=19.923(4),c=13.748(3)Å,β=92.30(3)°,V=1700.6(6)Å3,Dc=1.228 Mg/m3,Z=4,F(000)=672,μ(MoKα)=0.084 mm-1,R=0.0526 and wR=0.1259.3-(2΄-Fluoro-6΄-chloro-phenyl)-4-(2΄-methyl-2΄-ethyl-1΄,3΄-oxazole)-5-methyl isoxazole carboxamide(6b)crystallizes in triclinic system,space group P with a=7.8750(16),b=10.596(2),c=11.725(12)Å,β=102.05(3)°,V=859.5(3)Å3,Dc=1.363 Mg/m3,Z=2,F(000)=368,μ(MoKα)=0.250 mm-1,R=0.0738 and wR=0.1941.Both of the molecules prefer to form crystal packing through C–H…O hydrogen bonds.Compounds 6a and 6b show safener activity on maize against the injury of chlorsulfuron.

Synthesis of novel 1,3-oxazole derivatives with insect growth-inhibiting activities

Straightforward and direct synthesis of 2-substituted-5-oxazolecarbaldehydes was achieved by treating propargylamides with mercury（II）perchlorate as catalyst and ammonium cerium（IV）nitrate as oxidant agent through intramolecular cyclization.These structurally interesting outcomes beneft to synthesize2,5-disubstituted-1,3-oxazoles with armyworm growth regulating activities.

Design and Synthesis of Polyoxazole-based Macrocycles Tethered with a Phosphonate Group

We present the design and synthesis of polyoxazole-based macrocycles containing a phosphonate group.A reliable route was established that allows for convenient and versatile incorporation of various phosphonate functionalities such as phosphonate ester,acid,and salt at the macrocyclic ring periphery.Such unprecedented macrocyclic compounds are anticipated to be appealing candidates as telomerase inhibitors.

A Convenient Synthesis of 2-Arylnaphtho[1,2-d]oxazole Derivatives Promoted by Triethylamine

A variety of 2-arylnaphtho[ 1,2-d]oxazole derivatives were efficiently synthesized in moderate to high yields by the reaction of aromatic aldehydes with 1-amino-2-naphthol derivatives in the presence of triethylamine in refluxing ethanol in air. Seven new 2-arylnaphtho[1,2-d]oxazole derivatives were obtained and characterized by the spectral data and elemental analysis. In addition, the X-ray crystal structures of 2-[4-（N,N-dimethylamino）phenyl]naphtho[ 1,2-d] oxzole （3d） and 1, 1＇-bis（naphtho[ 1,2-d]oxazol-2-yl）ferrocene （3n） have been determined.