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Catechol Moieties (catechol + moiety)
Selected AbstractsIron(III) Chelation: Tuning of the pH Dependence by Mixed LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2003Anne-Marie Albrecht-Gary Abstract The iron(III) chelating properties of two heteropodands with 8-hydroxyquinoline and catechol binding groups were examined and compared to those of the corresponding homopodal analogues, O-TRENSOX and TRENCAMS. Like the parent homopodands, the two heteropodands are based on the TREN scaffold and the chelating units are connected by amide groups, TRENSOX2CAMS having two 8-hydroxyquinoline and one catechol arms and TRENSOXCAMS2 one 8-hydroxyquinoline and two catechol moieties. The aqueous coordination chemistry of these ligands was examined by potentiometric and spectrophotometric methods in combination with 1H NMR spectroscopy. The respective pFeIII values showed a cooperative effect of the mixed chelating units. Moreover, the pFeIII dependence on pH showed that the mixed ligands exhibit a higher complexing ability than the parent ligands over the pH range 5,9 which is of biological relevance. This result could be of great interest for medical applications. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Studies on the Biosynthesis of Bovilactone-4,4 and Related Fungal Meroterpenoids,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2008Martin Lang Abstract The initial step in the biosynthesis of suillin (1), boviquinone-4 (2) and bovilactone-4,4 (3) in Suillus species is the geranylgeranylation of 3,4-dihydroxybenzoic acid at the 2-position. Feeding experiments with advanced precursors have identified boviquinone-4 and deacetylsuillin (9) as building blocks for the dilactone and catechol moieties, respectively, of bovilactone-4,4 (3). In order to explain the failure of boviquinone-4 (2) to incorporate side-chain-labelled deacetylsuillin (9#), an alternative sequence for the formation of 2 is proposed. During these experiments an interesting change in metabolism was noticed: after administration of larger quantities of aromatic carboxylic acids, the boviquinone-4 present in the fruit bodies disappeared and de novo synthesis of bovilactone-4,4 occurred. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Thermodynamic Analysis of Receptors Based on Guanidinium/Boronic Acid Groups for the Complexation of Carboxylates, ,-Hydroxycarboxylates, and Diols: Driving Force for Binding and CooperativityCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004Sheryl L. Wiskur Dr. Abstract The thermodynamics of guanidinium and boronic acid interactions with carboxylates, ,-hydroxycarboxylates, and diols were studied by determination of the binding constants of a variety of different guests to four different hosts (7,10). Each host contains a different combination of guanidinium groups and boronic acids. The guests included molecules with carboxylate and/or diol moieties, such as citrate, tartrate, and fructose, among others. The Gibbs free energies of binding were determined by UV/Vis absorption spectroscopy, by use of indicator displacement assays. The receptor based on three guanidinium groups (7) was selective for the tricarboxylate guest. The receptors that incorporated boronic acids (8,10) had higher affinities for guests that included ,-hydroxycarboxylate and catechol moieties over guests containing only carboxylates or alkanediols. Isothermal titration calorimetry revealed the enthalpic and entropic contributions to the Gibbs free energies of binding. The binding of citrate and tartrate was investigated with hosts 7,10, for which all the binding events were exothermic, with positive entropy. Because of the selectivity of hosts 8,10, a simple boronic acid (14) was also investigated and determined to be selective for ,-hydroxycarboxylates and catechols over amino acids and alkanediols. Further, the cooperativity of 8 and 9 in binding tartrate was also investigated, revealing little or no cooperativity with 8, but negative cooperativity with 9. A linear entropy/enthalpy compensation relationship for all the hosts 7,10, 14, and the carboxylate-/diol-containing guests was also obtained. This relationship indicates that increasing enthalpy of binding is offset by similar losses in entropy for molecular recognition involving guanidinium and boronic acid groups. [source] Synthesis of (R)-(,)-2-Fluoronorapomorphine , A Precursor for the Synthesis of (R)-(,)-2-Fluoro- N -[11C]propylnorapomorphine for Evaluation as a Dopamine D2 Agonist Ligand for PET InvestigationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2005Kåre Søndergaard Abstract 2-Fluoronorapomorphine, the PET labelling precursor to 2-fluoro- N -[11C]propylnorapomorphine, was prepared in 13 steps from codeine in a total yield of 10,%. Codeine was converted in four steps into N -benzylnorcodeine which was oxidised by using the Swern protocol. Subsequent acid-catalysed rearrangement afforded N -benzylnormorphothebaine which was selectively triflylated at the 2-position and pivaloylated at the 11-position. The triflate underwent palladium-catalysed amination with benzophenone imine. Amination conditions required sequential base addition to give substantial conversion of the triflate to the corresponding N -substituted benzophenone imine. After acidic hydrolysis the resulting aniline was transformed into the 2-fluoro compound via the Balz,Schiemann reaction. Hydrogenolysis of the N -benzyl group followed by deprotection of the catechol moiety using BBr3 provided 2-fluoronorapomorphine. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Exothermic thermal reaction of dopamine with 3,5-dinitrobenzoic acidJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2003Yoshikatsu Ito Abstract Pyrolysis of the crystalline 1,:,1 molecular complex DA,dnba, which was prepared from cocrystallization of dopamine (DA) and 3,5-dinitrobenzoic acid (dnba), was studied. This cocrystal decomposed violently at the melting-point, leading to the formation of a black solid along with a tiny amount of 3-amino-5-nitrobenzoic acid (1). The pyrolysis reaction was followed by differential scanning calorimetry (DSC) and one large exothermic peak was observed at the decomposition temperature. In view of the DSC patterns for cocrystal DA,dnba and other compounds, it seems that both a catechol moiety and an amino group of DA in addition to a strong electron acceptor such as dnba are required for the appearance of the exothermic peak. On the basis of (a) elemental analysis of the black solid and (b) other pyrolysis experiments for cocrystals PA,dnba (PA: ,-phenylethylamine), BA,dnba (BA: benzylamine), DMDA,dnba (DMDA: O,O,-dimethyldopamine) and DHBA,dnba (DHBA: 3,4-dihydroxybenzylamine), it is assumed that the black solid was formed mainly through elimination of more than one molecule of water from one molecule of DA,dnba. Copyright © 2003 John Wiley & Sons, Ltd. [source] Bisubstrate Inhibitors of the Enzyme Catechol O -Methyltransferase (COMT): Efficient Inhibition Despite the Lack of a Nitro GroupCHEMBIOCHEM, Issue 9 2004Ralph Paulini A new generation of bisubstrate inhibitors for the S -adenosylmethionine- and magnesium ion-dependent enzyme catechol O -methyltransferase (COMT), feature binding affinities (IC50 values) in the double-digit nanomolar range despite the lack of a nitro group on the catechol moiety. Inhibitor potency does not directly correlate with the pKa value of the catechol HO groups and is strongly enhanced by hydrophobic aromatic substituents attached in a biaryl-type fashion to position 5 of the catechol ring. [source] | ||||||||||