Synthesis and tautomeric transformations of 2-(tert-butyl)-1,2,4-benzotriazine-3(2H)-thiones

Treatment of 2-(tert-butyl)-1,2,3,4-benzotetrazinium tetrafluoroborates with sodium thiocyanate afforded 2-(tert-butylazo)phenyl isothiocyanates 3, which exist in equilibrium with 2-(tert-butyl)-1,2,4-benzotriazine-3(2H)-thiones 3′. The equilibrium depends on the substituents R in the benzene ring: the percentage of the open isomer 3 is about 20% for R = H or Me; for R = Cl or Br, the equilibrium is completely shifted to cyclic isomer 3′. The equilibrium is slow on the time scale of the ¹H and ¹³C NMR experiments. For compounds 3a/3′a (R = H), the spectra at 24 °C show two sets of signals, while those at 0 °C contain only signals for isomer 3′a. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1192–1195, July, 2006.     

Synthesis of Protein Conjugates of 2-Carboxy-L-Arabinitol 5-Phosphate and 2-Carboxy-L-Ribitol 5-Phosphate

Abstract

The synthesis of 5-O-[5-(pentanoic acid)]-phosphono-L-erythro-pent-2-ulose 2 was successfully achieved by coupling benzyl 5-hydroxypentanoate 9b and 1-O-benzyl-L-erythro-pent-2-ulose ethane- 1,2-diyl dithioacetal 13 with the enediol pyrophosphate 18. Compound 2 was coupled to carrier proteins, porcine thyroglobuline and bovine serum albumin and the conjugates were treated with KCN to give conjugates of the hapten 1, designed to raise catalytic antibodies.     

Alkynylhalocarbenes

(Alk-1-ynyl)chlorocarbenes (3), generated from 1,1-dihaloalk-2-ynes and 3-substituted 3-bromo-1,1,1-trichloropropanes under the action of Bu^tOK in THF at 20°C, react with excess alkali metal alkoxide4 to give 3-substituted 2-(alk-1-ynyl)oxiranes (6) in 26–78% yields, most likely as a result of insertion of carbene3 into the α-C−H bond of alkoxides4 and subsequent cyclization of the resulting 1-substituted 2-chloro-2-(alk-1-ynyl)etoxides. The yields of oxiranes6 depend on the nature of the alkali metal used to prepare alkoxides4 and on the method employed for the preparation of the latter. For Part 2, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1185–1192, June, 1998.     

Synthesis and immunological study of a wall teichoic acid-based vaccine against E. faecium U0317

ABSTRACT

A repeat unit of cell wall teichoic acids (WTA) isolated from E. faecium U0317 was chemically synthesized efficiently by a stepwise strategy. It was derivatized with a 5-aminopentanyl linker to facilitate conjugation with carrier proteins KLH and HSA. Immunological studies of the KLH conjugate 1 demonstrated that it could provoke robust immune responses and high titers of IgG antibodies, which could successfully recognize the synthesized WTA repeat unit 3. This result suggested that synthetic glycoconjugate 1 could be a promising vaccine candidate against E. faecium for further studies.     

A NEW APPROACH TO A DISACCHARIDIC HAPTEN CONTAINING A GALACTOFURANOSYL ENTITY1-2

A short synthetic entry into the disaccharidic hapten β-D-Galf-(1→3)-α-D-Manp-O(CH₂)₈CO₂Me containing a galactofuranosyl entity at the non-reducing part is described. The synthetic scheme was designed in such a way that each required building block could be obtained by minimizing the number of chemical and purification steps. Indeed, compound 8 was obtained according to a four step–one pot preparation.     

Synthesis,crystal structure,spectroscopy, and electrochemistry of a uranium complex

A uranium coordination compound with pyridine-2,6-dicarboxylic acid in deionized water has been synthesized and characterized by IR, UV, XPS, and X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group C2/c with a?=?1.8427(4)?nm, b?=?0.6886(16)?nm, c?=?1.5442(4)?nm, α?=?90°, β?=?94.082(2)°, γ?=?90°, Z?=?4, and V?=?1.9544(8)?nm³. The structure shows an eight-coordinate uranium forming a hexagonal bi-pyramidal 3-D geometry with pyridine-2,6-dicarboxylate as building units. Fluorescent studies show several strong emissions. Cyclic voltammetric measurement of the compound reveals that uranium(VI) is reduced irreversibly at E _1/2?=?927?mV with ΔE _p?=?77?mV, E _1/2?=??289?mV with ΔE _p?=?113?mV. The electron transfer number (n) involved in reduction processes could be calculated to be approximately two and one, which corresponded to the unusual U(VI)/U(IV) and U(IV)/U(III) couples.     

Synthesis and fungicidal activity of 1,3,4-oxadiazol-2-yl thioether derivatives containing a phenazine-1-carboxylic acid scaffold

To find new higher fungicidal activities lead compounds and develop new eco-friendly agrochemicals, natural product phenazine-1-carboxylic acid (PCA) as scaffold, a series of 1,3,4-oxadiazol-2-yl thioether derivatives was synthesized and bio-assayed. The results reveal that most target compounds possessed moderate to good fungicidal activities against R. solani, S. sclerotioru and P. oryzac Cavgra. Compounds 6n and 6o exhibit more than 90% bioactivity against S. sclerotioru. The EC₅₀ value of compounds 6n and 6o are 11.16 and 30.47?μM respectively, in particular, compound 6n show equal activity against S. sclerotioru to PCA (10.49?μM). This result provides a valuable lead compound for further studies.     

Silylamido-Derivate von Eisen und Kobalt

Zusammenfassung FeCl₃ und CoCl₂ reagieren mit NaN[Si(CH₃)₃]₂ zu grün gefärbten, sublimierbaren bzw. destillierbaren monomeren Disilylmetallamiden der Zusammensetzung Fe{N[Si(CH₃)₃]₂}₃ (I) und Co{N[Si(CH₃)₃]₂}₂ (II). Die Verbindungen lösen sich leicht in organischen Lösungsmitteln und addieren keine weiteren Liganden.Gleichzeitig 5. Mitt. über silylsubstituierte Metallamide; 1. Mitt.:U. Wannagat undH. Niederprüm, Chem. Ber.94, 1540 (1961); 2. Mitt.:U. Wannagat undH. Kuckertz, Angew. Chem.75, 95 (1963); 3. Mitt.:J. Pump, E. G. Rochow undU. Wannagat, Angew. Chem.75, 374 (1963); 4. Mitt.:H. Bürger undU. Wannagat, Mh. Chem.94, 761 (1963).31. Mitt.:H. Bürger undU. Wannagat, Mh. Chem.94, 761 (1963).     

Mono-, Bis- und Tris(trimethylsilyl)hydroxylamin

Ohne ZusammenfassungMit 1 Abbildung77. Mitt.:U. Wannagat undM. Schulze, Z. Chem.8, 255 (1968).Vorläufige Mitt.:U. Wannagat, Angew. Chem.78, 648 (1966).Auszugsweise vorgetragen auf dem 155th National Meeting der American Chemical Society, San Francisco, April 1968.Sonderdrucke überU. W., D-33 Braunschweig, Pockelsstr. 4, Inst. für Anorg. Chem. der Techn. Universität.Mit Auszügen aus der DissertationO. Smrekar, Techn. Hochschule Graz 1969.     

Synthesis of novel azabicyclo derivatives containing a thiazole moiety and their biological activity against pine-wood nematodes

Abstract

To explore a new skeleton with nematicidal activity, a series of novel azabicyclo derivatives containing a thiazole moiety were designed, synthesized and evaluated for their nematicidal activities. The bioassay results against pine-wood nematodes (Bursaphelenchus xylophilus) showed that most of the title compounds displayed nematicidal activity at a concentration of 40?mg/L. Especially, the title compounds2-((8-methyl-8-azabicyclo[3.2.1]octan-3-yl)oxy)-4-(4-chlorophenyl)thiazole (7e), 2-((8-methyl-8-azabicyclo[3.2.1]octan-3-yl)thio)-4-phenylthiazole (10a) and 2-((8-methyl-8-azabicyclo [3.2.1]octan-3-yl)thio)-4-(4-chlorophenyl)thiazole (10e) exhibited more than 90% mortality against Bursaphelenchus xylophilus.     

Terrenolide S,a new antileishmanial butenolide from the endophytic fungus Aspergillus terreus

Terrenolide S, a new butenolide derivative (6), together with six known compounds: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (1), stigmast-4-ene-3-one (2), stigmasta-4,6,8(14),22-tetraen-3-one (3), terretonin A (4), terretonin (5) and butyrolactone VI (7) have been isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus (Asteraceae). Their structures were established by extensive spectroscopic analyses (1D, 2D NMR and HRESIMS), as well as optical rotation measurement and comparison with literature data. Compound 1 displayed a potent activity towards methicillin-resistant Staphylococcus aureus (MRSA) and Cryptococcus neoformans with IC₅₀ values of 2.29 and 10.68 µM, respectively. Moreover, 1, 2 and 6 exhibited antileishmanial activity towards Leishmania donovani with IC₅₀ values of 11.24, 15.32 and 27.27 µM, respectively and IC₉₀ values of 14.68, 40.56 and 167.03 µM, respectively.     

Syntheses,structures, and thermal properties of new Au(III) organometallic compounds with ancillary S-, O-, and/or N-donor ligands

((CH₃)₂Au)₂C₂O₄ (1), ((CH₃)₂AuSCN)₂ (2), (CH₃)₂AuSSP(OCH₃)₂ (3), and (CH₃)₂AuSSP(OC₂H₅)₂ (4) were prepared and recrystallized from hexane to determine their crystal structures and analyze them by thermal methods (TGA). The compounds have been investigated as new possible precursors for metal–organic chemical vapor deposition (MOCVD). Compounds 1 and 2 are solids, while 3 and 4 are liquids. Crystal structures of 1 and 2 have been studied by single-crystal X-ray diffraction (XRD): compounds are monoclinic, space group for 1 P2₁/c, for 2 P2₁/n. Compound 1 has crystal parameters a?=?7.6952(5)?Å, b?=?11.1814(8)?Å, c?=?12.2893(8)?Å, α?=?90°, β?=?104.922(4)°, γ?=?90°; 2 has crystal parameters a?=?5.6184(3)?Å, b?=?15.2744(6)?Å, c?=?6.9202(3)?Å, α?=?90°, β?=?102.864(2)°, γ?=?90°. These are neutral complexes, in which molecules are only connected by van der Waal's interactions. Thermal gravimetric analyses (TGA) have shown that 3 and 4 evaporate practically without decomposition. MOCVD experiments were carried out at lower pressure using 3 and 4 as precursors. The films were grown on Si substrate and investigated by XRD and SEM.     

New natural barrigenol-like triterpenoid isolated from the husks of Xanthoceras sorbifolia Bunge

The Xanthoceras sorbifolia Bunge husks were known for their abundant triterpenoids resource, which contributed to many bioactivities, such as antitumor, antiinflammatory and neuroprotection. The present study has led to the purification of a new triterpenoid saponin, 21β-O-acetyl-xanthohuskiside A (1), together with six known barrigenol derivatives (2–7), whose structures were authenticated on the basis of NMR, HR-MS, IR spectrum and acid hydrolysis experiment. Compound 7 showed more noteworthy cytotoxicity towards three human tumour cell lines (HCT-116, HepG-2 and U87-MG) than other compounds.     

Efficient Synthesis of a Water-Soluble Glucoamide Inhibitor Against Human Aldose Reductase by Click Chemistry

While D-glucose is the natural substrate of aldose reductase (AR) in the polyol pathway, the K _m value of D-glucose against AR is large. A glucoamide 1 was designed as a tool to investigate whether AR has a strong affinity for the open form of D-glucose. Glucoamide 1 was synthesized in high yield by modification of the reaction condition for click chemistry. It was found that our modified condition was applicable for highly polar alkynes and gave coupling products in excellent yield (90% to 100%). Although weak inhibitory activity against AR was observed, kinetic studies showed that AR does not accept glucoamide 1 in its active site.     

Cloning, expression, and sequence analysis of diaminopropionate ammonia lyase gene from a nonvirulentsalmonella typhimurium PU011

Background: Seeds ofLathyrus sativus, a legume plant, contain 3-oxalyl and 2,3-dioxalyl DAP (O-DAP), neurotoxins which when consumed causes Neurolathyrism or Osteolathyrism, in humans, affecting nervous system and bone formation respectively. Some microorganisms viz virulent and non-virulentSalmonella typhimurium, Salmonella typhi and Pseudomonad have been shown to detoxifyL-α,β-diaminopropionate (DAP), the immediate precursor of O-DAP. Result: The gene coding for diaminopropionate ammonia lyase (DAPAL) which detoxifies DAP was cloned from nonvirulentS. typhimurium PU011 intoEscherichia coli DH5α and the nucleotides sequenced (1212 bp). Whereas the specific enzyme activity of DAPAL obtained from recombinantE. coli PU018 was 0.346 U/mg, the specific activity of the enzyme from nonvirulentS. typhimurium PU011 was 0.351 U/mg. The DAPAL corresponding to 43 kDa protein was found both in nonvirulentS. typhimurium PU011 andE. coli PU018. The Km value was found to be 0.740 mM and 0.680 mM forS. typhimurium PU011 and 0.741 mM and 0.683 mM forE. coli PU018 when grown in minimal medium (MM+DAP) andL. sativus seed extracts respectively, indicating that both of them were capable of utilizing the neurotoxins present inL. sativus seeds. The biomass, enzyme production and the effect of pH and temperature on DAPAL enzyme activity from both non-virulentS. typhimurium PU011 andE. coli PU018 were found to be similar. Conclusion: The recombinantE. coli PU018 as well as non-virulentS. typhimurium PU011 are as good as pathogenicS. typhimurium in detoxifying DAP, the immediate precursor of O-DAP present inL. sativus seeds.     

Intramolecular O→Te and N→Te coordination bonds in molecules of β-tellurocyclohexenals and their nitrogen analogs

The structures of -tellurocyclohexenals and their nitrogen analogs, viz., -methyltellurocyclohexenal (6), -(4-ethoxyphenyltelluro)cyclohexenal (7), di(2-formylcyclohexen-1-yl) telluride (8), -(4-ethoxyphenyltelluro)cyclohexenylidene(4"-methylaniline) (9), -bromotellurenylcyclohexenylidene(4"-methylaniline) (10), and -bromotellurenylcyclohexenal (4-methylbenzoyl)hydrazone (11), were studied by X-ray diffraction analysis. Compounds 6—11 have a Z configuration at the double bond, which provides the formation of intramolecular OTe or NTe coordination bonds. The bonds about the Te atom have a T-shaped configuration. There is only one of two possible OTe coordination bonds in dialdehyde 8 and, consequently, this compound belongs to the 10-Te-3-tellurane structural type. Hydrazone 11 possesses both NTe and OTe intramolecular coordination bonds. Taking into account these interactions, the coordination polyhedron of the tellurium atom can be considered as a trigonal bipyramid. The intramolecular OTe or NTe coordination bond lengths in compounds 6 (2.692 ), 7 (2.657 ), 8 (2.657 ), and 9 (2.690 ) are 0.9—1.0 smaller than the sums of the van der Waals radii of the corresponding atoms. These bond lengths in compounds 10 (2.170 ) and 11 (2.203 ) are almost equal to the standard covalent bond length.     

Synthesis and cytotoxicity of new 2-oxo-7-phenyl-2,3-dihydrothiazolo[4,5-b]pyridine-5-carboxylic acid amides

Abstract

The synthesis and anticancer activity evaluation of new thiazolo[4,5-b]pyridine-5-carboxylic acid amides is described. The structures of the synthesized compounds were confirmed by spectroscopic data and a single crystal X-ray diffraction analysis for 2.4. The synthesized compounds were screened for their in vitro anticancer activity according to US NCI protocols. The most active 7-(4-fluorophenyl)-2-oxo-2,3-dihydrothiazolo[4,5-b]pyridine-5-carboxylic acid (4-chlorophenyl)amide 2.2 and 7-(4-chlorophenyl)-2-oxo-2,3-dihydrothiazolo[4,5-b]pyridine-5-carboxylic acid (4-chlorophenyl)amide 2.5 were screened for their cytotoxicity effects on C6 Rat glioma cells and U373 Human glioblastoma astrocytoma cells which revealed promising results comparable to temozolamide as reference control according MTT assay data.     

Cytotoxic constituents of Abutilon indicum leaves against U87MG human glioblastoma cells

The study was aimed to identify cytotoxic leads from Abutilon indicum leaves for treating glioblastoma. The petroleum ether extract, methanol extract (AIM), chloroform and ethyl acetate sub-fractions (AIM-C and AIM-E, respectively) prepared from AIM were tested for cytotoxicity on U87MG human glioblastoma cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. These extracts exhibited considerable activity (IC₅₀ values of 42.6–64.5 μg/mL). The most active AIM-C fraction was repeatedly chromatographed to yield four known compounds, methyl trans-p-coumarate (1), methyl caffeate (2), syringic acid (3) and pinellic acid (4). Cell viability assay of 1–4 against U87MG cells indicated 2 as most active (IC₅₀ value of 8.2 μg/mL), whereas the other three compounds were much less active. Interestingly, compounds 1–4 were non-toxic towards normal human cells (HEK-293). The content of 2 in AIM-C was estimated as 3% by HPLC. Hence, presence of some more active substances besides methyl caffeate (2) in AIM-C is anticipated.     

New Synthetic Route to (1S)-4,5-Dimethoxy-1-[(methylamino)methyl] Benzocyclobutane,a Key Intermediate of Ivabradine

An efficient process for the preparation of (1S)-4,5-dimethoxy-1-[(methylamino)methyl] benzocyclobutane (S)-3 as ivabradine intermediate, which was obtained in 56% yield, is described. The salient feature of this process is the racemization of the undesired (1R)-4,5–dimethoxy-1,2-dihydrocyclobutabenzene-1-carboxylic acid (R)-12, and the overall yield of (S)-12 was improved to 70% by three resolutions of the racemized acid with R-(α)-phenylethanamine. The reduction of amide (S)-13 was achieved with NaBH₄-I₂ in refluxing tetrahydrofuran, giving the corresponding amine (S)-3 in 90% yield. The improved synthetic route described herein is cost-efficient, environmentally friendly and feasibile for scale-up production.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Generation of antiserum to Irgarol 1051 and development of a sensitive enzyme immunoassay using a new heterologous hapten derivative

A polyclonal antiserum to Irgarol 1051 was developed in sheep and used to construct an enzyme immunoassay method for the measurement of the antifouling compound in river and seawater samples. The antiserum was generated by a hapten derivative, 2-(tert-butylamino)-4-(cyclopropylamino)-6-(thiopropionic acid)-1,3,5-triazine, coupled to a mixture of keyhole limpet hemocyanin and bovine serum albumin, and the competitive enzyme immunoassay was constructed using a plate-coating antigen made of a heterologous new hapten derivative, 2-(tert-butylamino)-4-(cyclopropylamino)-6-(phenoxybenzoic acid)-1,3,5-triazine, linked to gelatine. The assay showed a sensitivity of about 5 ng L^–1 in river and seawater matrices with reasonable specificity with respect to commonly used triazines such as atrazine (3%), simazine (>0.1%) and desethylatrazine (>0.01%). However, high cross-reactivity levels were found with ametryn (56%) and prometryn (60%). Tests on the effects of organic solvents on assay performance indicated a high tolerance to methanol but much less so to acetonitrile. The assay was found to be highly reproducible and robust owing to the stability of the sheep antibody and the highly optimised competitive assay reagents which included the use of the new triazine-O-phenoxybenzoic acid derivative.