Search results for "Configuration"
showing 10 items of 601 documents
ChemInform Abstract: Two-Carbon Bridge Substituted Cocaines: Enantioselective Synthesis, Attribution of the Absolute Configuration, and Biological Ac…
2010
In an effort to learn more about the general structure-activity relationships of cocaine with the aim to elucidate those structural features that might confer antagonistic properties to such analogues, we describe herein our synthetic efforts to prepare two-carbon bridge functionalized (methoxylated and hydroxylated) analogues. Our approach makes use of a modification of the classical Willstatter synthesis of cocaine: Mannich type cyclization of acetonedicarboxylic acid monomethyl ester with methylamine hydrochloride and 2-methoxysuccindialdehyde in a citrate buffer solution afforded the 6- and 7-substituted 2-carbomethoxy-3-tropinones 3a,b and 4a,b in approximate yields of 64%. Reduction o…
Struktur-Wirkungs-Beziehungen bei Histaminanaloga, 22. Mitt. Absolute Konfiguration und histaminartige Wirkung der enantiomeren α, Nα-Dimethylhistami…
1980
Es werden die Synthesen der enantiomeren α, Nα-Dimethylhistamine (+)—3 und (−)—3, die Ableitung der absoluten Konfiguration sowie die histaminartige Wirksamkeit der Enantiomere am Ileum (H1) und Atrium (H2) des Meerschweinchens beschrieben. Structure-Activity Relationship of Histamine Analogues. XXII: Absolute Configuration and Histamine-like Activity of the Enantiomeric α, Nα-Dimethylhistamines The synthesis of the enantiomeric α, Nα-Dimethylhistamines (+)—3 and (−)—3, the determination of the absolute configuration and the histamine-like activity of the enantiomers on the guinea-pig ileum (H1) and atrium (H2) are reported.
Struktur-Wirkungs-Beziehungen bei Histaminanaloga, 23. Mitt. Absolute Konfiguration und histaminartige Wirkung der enantiomeren α-Chlormethylhistamin…
1981
Es wird die histaminartige Wirksamkeit der enantiomeren α-Chlormethylhistamine (+)-2a und (−)-2a sowie der Nα-Methyl-α-chlormethylhistamine (+)-2b und (−)-2b am Ileum (H1) und Atrium (H2) des Meerschweinchens beschrieben und die absolute Konfiguration der Enantiomere abgeleitet. Structure-Activity Relationships of Histamine Analogues, XXIII: Absolute Configuration and Histamine-like Activity of the Enantiomeric α-Chloromethylhistamines and Nα-Methyl-α-chloromethylhistamines The histamine-like activities of the enantiomeric α-chloromethylhistamines (+)-2a and (−)-2a and of the Nα-methyl-α-chloromethylhistamines (+)-2b and (−)-2b on the guinea pig ileum (H1) and atrium (H2) are reported. The …
Towards a converged barrier height for the entrance channel transition state of the N(2D)+CH4 reaction and its implication for the chemistry in Titan…
2011
Abstract The N( 2 D) + CH 4 reaction appears to be a key reaction for the chemistry of Titan’s atmosphere, opening the door to nitrile formation as recently observed by the Cassini–Huygens mission. Faced to the controversy concerning the existence or not of a potential barrier for this reaction, we have carried out accurate ab initio calculations by means of multi-state multi-reference configuration interaction (MS-MR-SDCI) method. These calculations have been partially corrected for the size-consistency errors (SCE) by Davidson, Pople or AQCC corrections. We suggest a barrier height of 3.86 ± 0.84 kJ/mol, including ZPE, for the entrance transition state, in good agreement with the experime…
Les résultats des élections professionnelles dans les entreprises du secteur privé (2013-2016)
2019
International audience
Construction stages of cable-stayed bridges with composite deck
2012
A cable-stayed bridge is built by following a construction sequence of different subsequent stages that imply changes of the geometric configuration, restraints and consequently stress and strain patterns. A study is presented about stay stressing sequences in cable-stayed bridges with composite deck for the case of construction made by the cantilever method. Initial cable forces are found through partial elastic schemes of construction stages. Different stay stressing procedures are implemented and a comparison between them is proposed in order to evaluate the differences in terms of deformed shape and internal force distribution of the deck and the pylon. Results can be useful to give pra…
Crystal structure of (R)-6-fluoro-2-[(S)-oxiran-2-yl]chroman
2015
The title compound, C11H11FO2, is a building block in the synthesis of the active pharmaceutical ingredient DL-nebivolol. The synthesis starting from the enantiomerically pure (R)-6-fluoro-4-oxo-3,4-dihydro-2H-chromene-2-carboxylic acid resulted in a mixture of two stereoisomers, namely (R)-6-fluoro-2-[(S)-oxiran-2-yl]chroman and (R)-6-fluoro-2-[(R)-oxiran-2-yl]chroman. The mixture was separated by column chromatography but only one stereoisomer crystallized. The X-ray structure analysis revealed that the solid consisted of theR,Sisomer. A similar procedure was repeated for (S)-6-fluoro-4-oxo-3,4-dihydro-2H-chromene-2-carboxylic acid and, in this case, theS,Risomer was produced as a crystal…
Crystal structure and absolute configuration of (3aR,3′aR,7aS,7′aS)-2,2,2′,2′-tetramethyl-3a,6,7,7a,3′a,6′,7′,7′a-octahydro-4,4′-bi[1,3-benzodioxolyl…
2017
The absolute configuration,i.e.(3aR,3′aR,7aS,7′aS), of the title compound, C18H26O4, synthesizedviaa palladium-catalyzed homocoupling reaction, was determined on the basis of the synthetic pathway and was confirmed by X-ray diffraction. The homocoupled molecule is formed by two chemically identical moieties built up from two five- and six-membered fused rings. The supramolecular assembly is controlled mainly by C—H...O interactions that lead to the formation of hydrogen-bonded chains of molecules along the [001] direction, while weak dipolar interactions and van der Waals forces hold the chains together in the crystal structure.
1,1′-(Diphosphene-1,2-diyl)bis(2,2,6,6-tetramethylpiperidine)
2017
The title compound, C18H36N2P2, crystallizes in the triclinic space groupP-1 with two independent molecules in the asymmetric unit. Both molecules adopt atransconfiguration of the tetramethylpiperidine units along the P=P axis. The crystal packing is stabilized only by van der Waals interactions.
Crystal structure and absolute configuration of (4S,5R,6S)-4,5,6-trihydroxy-3-methylcyclohex-2-enone (gabosine H)
2017
The absolute configuration of the title compound, determined as 4S,5R,6S on the basis of the synthetic pathway, was confirmed by single-crystal X-ray diffraction. The molecule is formed by a substituted six-membered cyclohexene ring adopting an envelope conformation and substituted by carbonyl, methyl and hydroxyl groups. The supramolecular structure is mainly built by a combination of O—H⋯O and weaker C—H⋯O hydrogen bonds.