Condensed thiazoles,II: Synthesis of 7-substituted thiazolo[4,5-d]pyrimidines as possible anti-HIV,anticancer, and antimicrobial agents

Summary Some 3-substituted 2-thioxothiazolo[4,5-d]pyrimidin-7(6H)-ones (2a,b;4) have been synthesized and converted to their 7-chloro (3,5), 7-diethanolamino (6a,b), 7-bis(2-chloroethyl)amino (7), 7-azido (8), 7-amino (9), 7-hydrazino (16), 7-mercapto (11a,b), and 7-methylthio (12) derivatives. These compounds were evaluated for theirin vitro antimicrobial, anti-HIV; and anticancer activities.For part I of this series, see Monatsh Chem127: 1203     

The Effect of Different Ethoxylations for Sorbitan Monolaurate on Enhancing Simultaneous Saccharification and Fermentation (SSF) of Wheat Straw to Ethanol

In this paper, four nonionic surfactants with different hydrophilic–lipophilic balance (HLB) based on sorbitan monolaurate were synthesized by introducing ethylene oxide gas (n = 20, 40, 60, and 80 ethylene oxide units). The chemical structure of the prepared ethoxylated surfactants was confirmed using Fourier transform-infrared and ¹H NMR spectroscopes. The surface tension and thermodynamic properties of the prepared surfactants have been studied. The simultaneous saccharification and fermentation (SSF) process for ethanol production from microwave/alkali pretreated wheat straw has been assayed using nonionic surfactants have different ethylene oxide units. Ethanol yield was 82% and 61% for Kluyveromyces marxianus and Saccharomyces cerevisiae, respectively, with the addition of 2.5 g/l of the prepared nonionic surfactant (HLB = 18.2). Results show that the production of ethanol from microwave/alkali pretreated wheat straw increased with increasing the (HLB) value of the nonionic surfactant.     

Photoluminescence of Uranium(VI): Quenching Mechanism and Role of Uranium(V)

The photoluminescence of uranium(VI) is observed typically in the wavelength range 400–650 nm with the lifetime of several hundreds μs and is known to be quenched in the presence of various halide ions (case A) or alcohols (case B). Here, we show by density functional theory (DFT) calculations that the quenching involves an intermediate triplet excited state that exhibits uranium(V) character. The DFT results are consistent with previous experimental findings suggesting the presence of photoexcited uranium(V) radical pair during the quenching process. In the ground state of uranyl(VI) halides, the ligand contributions to the highest occupied molecular orbitals increase with the atomic number (Z) of halide ion allowing larger ligand‐to‐metal charge transfer (LMCT) between uranium and the halide ion. Consequently, a larger quenching effect is expected as Z increases. The quenching mechanism is essentially the same in cases A and B, and is driven by an electron transfer from the quencher to the UO₂²⁺ entity. The relative energetic stabilities of the triplet excited state define the “fate” of uranium, so that in case A uranium(V) is oxidized back to uranium(VI), while in case B uranium remains as pentavalent.     

DNA-Mediated Stack Formation of Nanodiscs

Membrane-scaffolding proteins (MSPs) derived from apolipoprotein A-1 have become a versatile tool in generating nano-sized discoidal membrane mimetics (nanodiscs) for membrane protein research. Recent efforts have aimed at exploiting their controlled lipid protein ratio and size distribution to arrange membrane proteins in regular supramolecular structures for diffraction studies. Thereby, direct membrane protein crystallization, which has remained the limiting factor in structure determination of membrane proteins, would be circumvented. We describe here the formation of multimers of membrane-scaffolding protein MSP1D1-bounded nanodiscs using the thiol reactivity of engineered cysteines. The mutated positions N42 and K163 in MSP1D1 were chosen to support chemical modification as evidenced by fluorescent labeling with pyrene. Minimal interference with the nanodisc formation and structure was demonstrated by circular dichroism spectroscopy, differential light scattering and size exclusion chromatography. The direct disulphide bond formation of nanodiscs formed by the MSP1D1_N42C variant led to dimers and trimers with low yield. In contrast, transmission electron microscopy revealed that the attachment of oligonucleotides to the engineered cysteines of MSP1D1 allowed the growth of submicron-sized tracts of stacked nanodiscs through the hybridization of nanodisc populations carrying complementary strands and a flexible spacer.     

Polarographic behaviour of α- and γ-substituted acetoacetanilide derivatives in alcoholic aqueous media

A polarographic study on a series of newly synthesized compounds, namely N-(3-pyridyl)-2,3-dioxobutanamide-2-arylhydrazones (1 a–f) in a wide range ofpH is reported and discussed. CPE indicated that these compounds are reduced in the hydrazono form. A scheme is proposed and confirmed through isolation and identification of 2,5-dimethyl-3,6-di[N-(3-pyridyl)amide]-1,4-dihydro-pyrazine as an electrolysis product.

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Das polarographische Verhalten von - und -substituierten Acetoacetanilid-Derivaten in alkoholisch-wäßrigem Medium

Zusammenfassung Es wird über eine polarographische Untersuchung einer Reihe von neu synthetisierten Verbindungen, die N-(3-pyridyl)-acetoacetamid--arylhydrazone1 a–fbd, in einem weitenpH-Bereich berichtet. Kontrollierte Potential-Elektrolyse (CPE) zeigte, daß diese Verbindungen in ihrer Hydrazonoform reduziert werden. Es wird ein Reaktionsschema vorgeschlagen und auch mit der Isolierung und Identifizierung von 2,5-Dimethyl-3,6-di[N-(3-pyridyl)amid]-1,4-dihydropyrazin als Elektrolyseprodukt belegt.

     

A novel synthesis for quinoline derivatives

Condensation of ethyl 2-(2-oxo-2,3-dihydro-1H-indolid-3-ene)cyanoacetate and/or 2-(2-oxo-2,3-dihydro-1H-indolid-2-ene)malononitrile with 3-methylpyrazolin-5-one, 1-phenyl-3-methyl-pyrazolin-5-one, benzoyl acetonitrile or ethyl acetoacetate affords different substituted quinolines. The reaction is suggested to proceed through a nucleophilic addition followed by ring opening and recyclization steps.     

Electroreduction of the activated olefinic double bond in some 2-aryl-1(2-acetylamino-1,3,4-thiadiazol-5-yl)-propionitrile derivatives

The electrochemical reduction of a series of the title compounds has been investigated in alcoholic buffered media at the DME. A mechanism for the reduction process has been proposed and confirmed through spectrophotometric and potentiometricpKa determinations and identification of CPE products. A trial to calculate the kinetic parameterk _f,h ^o by different methods is included.

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Elektroreduktion der aktivierten olefinischen Doppelbindung in einigen 2-Aryl-1(2-acetylamino-1,3,4-thiadiazol-5-yl)-propionitril-Derivaten

Zusammenfassung Es wurde die elektrochemische Reduktion einer Serie der Titelverbindungen in alkoholischer, gepufferter Lösung an der tropfenden Quecksilberelektrode untersucht. Ein Mechanismus für den Reduktionsprozeß wird vorgeschlagen, der auf Befunde spektrophotometrischer und potentiometrischerpKa-Messungen und die Identifizierung von Produkten der kontrollierten Potentialelektrolyse (CPE) gestützt ist. Ein Versuch zur Ermittlung der kinetischen Parameterk _f,h ^o mit verschiedenen Methoden wurde unternommen.

     

Reactions with the Arylhydrazones of α-Cyanoketones: The Structure of 2-Arylhydrazono-3-ketimino-nitriles

Analysis of the IR., UV., and polarographic data of a variety of 2-arylhydrazono-3-ketimino-nitriles indicated that these derivatives exist mainly in the intramolecularly chelated hydrazone structure 1 . Compounds 1 reacted with hydrazine hydrate to yield the corresponding 5-amino-4-arylazopyrazoles ( 3 ). Compounds 3a reacted with acetylacetone, ethyl acetoacetate, and diethyl malonate to yield the pyrazolo[1, 5-a]pyrimidine derivatives 4, 5 , and 7 respectively. Compound 3a also reacted with benzoylisothiocyanate to yield the pyrazolyl thiourea derivative 8 .