- Nicotinic acid adenine dinucleotide phosphate analogues substituted on the nicotinic acid and adenine ribosides. Effects on receptormediated Ca2+ release
-
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a Ca2+ releasing intracellular second messenger in both mammals and echinoderms. We report that large functionalized substituents introduced at the nicotinic acid 5-position are recognize
- Trabbic, Christopher J.,Zhang, Fan,Walseth, Timothy F.,Slama, James T.
-
p. 3593 - 3610
(2015/05/05)
-
- Investigation of Electronic Effects in the Pyridine and Pyridine N-Oxide Rings. Part 4. Kinetics and Mechanism of the Reaction of Diazodiphenylmethane with Substituted Carboxypyridine and 2-carboxypyridine N-Oxides in Dimethylforamide
-
Rate constants for the reaction of 15 substituted carboxypyridines and four substituted 2-carboxypyridine N-oxides with diazodiphenylmethane (DDM) in dimethylformamide (DMF) were determined at 30 deg C, by the known spectrophotometric method.For comparison, rate constants for the raection of 12 substituted benzoic acids were determined under the same conditions.Kinetic and thermodynamic parameters obtained, together with products analyses, essentially verify the previously proposed reaction mechanism in this solvent.The empirical Hammett treatment has benn applied to the results, and it was shown that a scattered overall plot (ρ=1.019, log ko=-2.98, r=0.91, s=0.22, n=31) was obtained with additive ? constants from the corresponding ? values for the pyridine aza-group and N-oxide group and Hammett ? constants for substituents.Fairly good separate correlations were obtained from the data for substituted benzoic acids (ρ=1.07, log ko=-2.91, r=0.985, s=0.12, n=12), halogen- and nitro-substituted acids (ρ=1.18, log ko=-3.35, r=0.995, s=0.04, n=4).A far less satisfactory correlation was obtained when it was applied to the substituted carboxypyridines, including the N-oxides (ρ=1.15, log ko=-3.35, r=0.91, s=0.18, n=19).It was concluded that powerful solvent nucleophilic stabilisation of the reactant carboxylic acid in the initial state is greatly influenced by the type of substitution, substituent solvation, and probably also by the kind of electronic interaction of the particular substituent with the heteroaromatic nuclei.
- Radojkovic-Velickovic, Mirjana,Misic-Vukovic, Milica
-
p. 1975 - 1977
(2007/10/02)
-
- Hydroxy- and amino-substituted piperidinecarboxylic acids as γ-aminobutyric acid agonists and uptake inhibitors
-
The syntheses of (3RS, 4RS)-4-hydroxypiperidine-3-carboxylic acid (4), (3RS, 5SRJ-5-hydroxypiperiden-3-carboxylic acid (20), (3RS, 4SR)-4-acetamidopiperidine-3-carboxylic acid (10), and (3RS, 5SR)-5-acetamidopiperidine-3-carboxylic acid (18), related to the specific γ-aminobutyric (GABA) uptake inhibitors (RS)-piperidine-3-carboxylic acid (nipecotic acid) and (3RS, 4SR)-4-hydroxypiperidine-3-carboxylic acid (21), are described. Furthermore, (3RS, 4SR)-3-hydroxypiperidine-4-carboxylic acid (14), related to the specific GABA agonist piperidine-4-carboxylic acid (isonipecotic acid), has been synthesized. The structures of 4, 10, 14, 18, and 20 have been established by 270-MHz 1H NMR spectroscopic analyses. The affinity of the compounds for the GABA receptors and for the neuronal (synaptosomal) GABA uptake system in vitro has been measured. Compound 14 interacts selectively with the GABA receptors but less effectively than isonipecotic acid and the cis-isomer 22. Compounds 4, 18, and 20 are inhibitors of the GABA uptake system, although much weaker than nipecotic acid and (3RS, 4SR)-4-hydroxypiperidine-3-carboxylic acid (21). Compound 10 is inactive in both test systems.
- Jacobsen,Labouta,Schaumburg,Falch,Krogsgaard-Larsen
-
p. 1157 - 1162
(2007/10/02)
-