Cabibbo-angle-favored decays:D→SP

We have studiedD→K ₀ ^* π andD→Ka ₀ decays in the factorization approximation. The spectator model leads to a color-suppression of \(D^0 \to \bar K_0^{*0} \pi ^0 \) . However, due to the smallness off _{a 0}, a similar suppression does not occur for \(D^0 \to \bar K^0 a_0^0 \) . We show that the inclusion of annihilation contribution can lift the color-suppression of \(D^0 \to \bar K_0^{*0} \pi ^0 \) . We also include final state interactions in a dynamical model whereK (1830) pole in the direct channel dominates the annihilation process.     

Acetylene chemistry. Part 29. A convenient synthesis of 9-(n-alkynyl)acridinamines via a nucleophilic displacement reaction between 9-chloroacridine and N-alkynyl amines

Three new 9-(N-alkynyl)acridinamines 5, 6 and 7 have been synthesized from 9-chloroacridine using a simple aromatic nucleophilic substitution reaction.     

Stoichiometry,product and kinetics of catalytic oxidation of 2,6–dimethylphenol by bromo(N,N′- diethylethylenediamine)copper complexes in methylene chloride

Copper(I) dimer [(DEED)CuBr]2 (4, DEED=N,N-diethylethylenediamine) is rapidly oxidized by O2 to mixed valence peroxocopper complex [(DEED)CuBr]4O2 (1) in CH2Cl2 at –50 to 30°C. The long half- life for conversion of (1) into oxocopper(II) complex [(DEED)]CuBr]2O (3) allows (1), (3) and their carbonato derivative of [(DEED)CuBr]2CO3 (5) to be compared as oxidants of 2,6–dimethylphenol (DMPOH) to the corresponding diphenoquinone (DPQ) over a range of concentrations and temperatures. DPQ production is: 1)less than stoichiometric with deficits or slight excesses of DMPOH, but 2) mildly catalytic at moderate [DMPOH], as found with tetranuclear oxo-halo(pyridine)copper(II) oxidants. This behaviour is attributed to 1) co-product water destruction of initiators, and 2) inhibition by water of copper(I) reoxidation to complete the catalytic cycle. These inhibiting factors apparently are ameliorated by water incorporation in hydrogen-bonded phenol clusters in aprotic solvents. Initial rate measurements show that (1), (3) and (5) form monophenolate complexes with DMPOH in methylene chloride. The rate-determining step for conversion of these complexes to DPQ is fastest for oxocopper(II) complex (3) which is expected to be the strongest proticbase. Highest rates with (3) and activation parameter comparisons suggest that the ability of phenolatocoppercomplexes to accept protons from coordinated phenolate is an important factor in determining overall copper- catalyzed phenolic oxidative coupling rates.     

Comparison of the voltammetric studies at mercury and glassy carbon electrodes for the interaction of lumichrome with DNA and analytical applications

The determination of the interaction between lumichrome (LC), one of the products of decomposition of the biologically important flavins, and calf thymus double-stranded DNA was performed by using cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV) in connection with a hanging mercury drop electrode (HMDE) or glassy carbon electrode (GCE). The nature of the process taking place at both electrode surfaces was clarified. It was found that the addition of DNA to a buffered LC solution results in the decrease of redox peak currents with changes in the peak potentials at both electrodes. We assume that LC interacting with DNA produces an electrochemically inactive supramolecular complex via intercalation. There was a difference between the electrochemical parameters determined at the HMDE and those at the GCE. The binding constants ( K) of the LC-DNA complex at HMDE and GCE were determined through the changes of peak currents and their values at the 10(5) level and 10(4) level with each nucleotide residue of DNA binding one LC molecule, respectively. Furthermore, the calibration graph for the determination of DNA was obtained by the decrease in the DPSV peak current of LC in the presence of DNA. Different variables, such as the concentration of LC, the accumulation time and solution conditions, were studied and optimised to maximize the sensitivity; in addition, the detection limit and the reproducibility were determined.     

Synthesis of 3 10-helix-inducing constrained analogues of L-proline

A bicyclic indolizidinone carboxylic acid and a tricyclic constrained analogue of l-proline were synthesized and evaluated for their ability to induce helix formation as l-Ala tetrapeptides. Variable-temperature NMR, DMSO titration, CD spectra, and X-ray structure analyses, in conjunction with molecular modeling, confirmed the existence of 3(10)-helical motifs with di- and tetrapeptides of l-Ala.     

Natural product chemistry. Part 116. Synthesis of daurine and folidine: Two 2(1H)-quinolinone alkaloids fromHaplophyllum species

Structures of the recently isolated 2(1H)-quinolinone alkaloids, daurine and folidine have been confirmed by total synthesis.

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Naturstoffchemie. 116. Mitt.: Synthese des Daurins und Folidins, 2(1H)-Chinolinon-Alkaloide aus Haplophyllum Spezies

Zusammenfassung Die Strukturen der kürzlich aufgefundenen 2(1H)-Chinolinon-Alkaloide Daurin und Folidin konnten durch Totalsynthese bestätigt werden.

     

Structure of plumbazeylanone: a novel trimer of plumbagin from plumbago zeylanica

Plumbazeylanone, a quinone from Plumbago zeylanica is probably 5b,11a,12,12a-tetrahydro-1,7-dihydroxy-5b-(8-hydroxy-3-methyl-1,4-naphthoquinon-2-yl)-5a,12a-dimethyl-5a$\text{H}$-dibenzo[$\text{b}$,$\text{h}$]fluorene-5,13:6,11-diquinone, a novel trimer of plumbagin with an additional methyl group.     

Electrolytic partial fluorination of organic compounds. 79. Anodic fluorination of spiropyrazoline-5,3'-chroman-4-ones and thiochromanone analogues. A route to aroyl fluoride derivatives

[reaction: see text] Anodic fluorination of spiropyrazole-5,3'-chroman-4-ones and their thiochromanone analogues in dimethoxyethane containing Et4NF x 4HF resulted in ring opening of spiroheterocycles, which led to the formation of (5-pyrazolyl)methyl o-carbomethoxyphenyl ethers and their thioether analogues via benzoyl fluoride derivatives.     

Chemoenzymatic synthesis of enantiomerically enriched kavalactones

Lipase-mediated kinetic resolution of methyl-3-hydroxy-5-phenylpentanoate and (6E)-ethyl 5-hydroxy-3-oxo-7-phenylhept-6-enoate is described in high enantiomeric excess and good yields. The effect of different lipases in different solvents has been screened using different acylating agents. This protocol has been extended for the preparation of enantiomerically pure biologically important kavalactones.