- Lewis basicity modulation of N-heterocycles: A key for successful cross-metathesis
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Cross-metathesis involving N-heteroaromatic olefinic derivatives is disclosed. The introduction of an appropriate substituent on the heteroaromatic ring decreases the Lewis basicity of the nitrogen atom, thus preventing the deactivation of the ruthenium-centered catalyst. The reaction is quite general in terms of both N-heterocycles and olefinic partners.
- Lafaye, Kevin,Nicolas, Lionel,Gurinot, Amandine,Reymond, Sbastien,Cossy, Janine
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supporting information
p. 4972 - 4975
(2015/01/08)
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- Characterization of nicotinamidases: Steady state kinetic parameters, classwide inhibition by nicotinaldehydes, and catalytic mechanism
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Nicotinamidases are metabolic enzymes that hydrolyze nicotinamide to nicotinic acid. These enzymes are widely distributed across biology, with examples found encoded in the genomes of Mycobacteria, Archaea, Eubacteria, Protozoa, yeast, and invertebrates, but there are none found in mammals. Although recent structural work has improved our understanding of these enzymes, their catalytic mechanism is still not well understood. Recent data show that nicotinamidases are required for the growth and virulence of several pathogenic microbes. The enzymes of Saccharomyces cerevisiae, Drosophila melanogaster, and Caenorhabditis elegans regulate life span in their respective organisms, consistent with proposed roles in the regulation of NAD+ metabolism and organismal aging. In this work, the steady state kinetic parameters of nicotinamidase enzymes from C. elegans, Sa. cerevisiae, Streptococcus pneumoniae (a pathogen responsible for human pneumonia), Borrelia burgdorferi (the pathogen that causes Lyme disease), and Plasmodium falciparum (responsible for most human malaria) are reported. Nicotinamidases are generally efficient catalysts with steady state kcat values typically exceeding 1 s -1. The Km values for nicotinamide are low and in the range of 2 -110 μM. Nicotinaldehyde was determined to be a potent competitive inhibitor of these enzymes, binding in the low micromolar to low nanomolar range for all nicotinamidases tested. A variety of nicotinaldehyde derivatives were synthesized and evaluated as inhibitors in kinetic assays. Inhibitions are consistent with reaction of the universally conserved catalytic Cys on each enzyme with the aldehyde carbonyl carbon to form a thiohemiacetal complex that is stabilized by a conserved oxyanion hole. The S. pneumoniae nicotinamidase can catalyze exchange of 18O into the carboxy oxygens of nicotinic acid with H218O. The collected data, along with kinetic analysis of several mutants, allowed us to propose a catalytic mechanism that explains nicotinamidase and nicotinic acid 18O exchange chemistry for the S. pneumoniae enzyme involving key catalytic residues, a catalytic transition metal ion, and the intermediacy of a thioester intermediate.
- French, Jarrod B.,Cen, Yana,Vrablik, Tracy L.,Xu, Ping,Allen, Eleanor,Hanna-Rose, Wendy,Sauve, Anthony A.
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experimental part
p. 10421 - 10439
(2011/10/07)
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- TRPA1 ANTAGONISTS
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Compounds of formula (I), wherein R1, R2, R3, and Y are defined in the description are TRPA1 antagonists. Compositions comprising such compounds and methods for treating conditions and disorders using such compounds and compositions are also disclosed.
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Page/Page column 28; 30
(2009/09/04)
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- MELANIN-CONCENTRATING HORMONE RECEPTOR ANTAGONISTS CONTAINING PIPERIDINE DERIVATIVES AS THE ACTIVE INGREDIENT
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The invention provides melanin-concentrating hormone receptor antagonists containing as the active ingredient piperidine derivatives represented by the general formula [I]: ???[wherein R1 is hydrogen, hydroxyl, lower alkyl, or the like; R2, R3a, R3b, R4a, R4b, R5a, R5b and R6 each stands for hydrogen, halogen, or the like; W1 and W2 each independently stands for -O-, -CH2-, or the like; Y1, Y2, Y3 and Y4 stand for -CH-, -CF-, -N-, or the like; Z stands for lower alkyl, an aliphatic heterocyclic group, or the like; Ar is a mono- or bi-cyclic aliphatic heterocycle or an aromatic heterocycle; and n is an integer of 1 to 8]. The compounds act as antagonist against melanin-concentrating hormone receptor and are useful as drugs for central diseases, circulatory diseases, or metabolic diseases.
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Page/Page column 31
(2010/02/14)
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