Search results for "Asymmetric"
showing 10 items of 241 documents
Stereoselective Synthesis of Spiro-Decalin Oxindole Derivatives via Sequential Organocatalytic Michael-Domino Michael/Aldol Reaction.
2022
A highly stereoselective procedure for the synthesis of spiro-polycyclic oxindoles bearing five contiguous stereogenic centers including two tetrasubstituted carbons has been developed. Under sequential organocatalysis performed by a pyrrolidine-based organocatalyst and DBU, a highly atom-economical Michael–domino Michael/aldol reaction sequence was optimized, yielding variously functionalized spiro-decalin oxindoles with excellent stereoselectivity (>99:1 dr, up to 92% ee). peerReviewed
[3 + 2] Cycloadditions in Asymmetric Synthesis of Spirooxindole Hybrids Linked to Triazole and Ferrocene Units: X-ray Crystal Structure and MEDT Stud…
2022
Derivatization of spirooxindole having triazole and ferrocene units was achieved by the [3 + 2] cycloaddition (32CA) reaction approach. Reacting the respective azomethine ylide (AY) intermediate generated in situ with the ethylene derivative produced novel asymmetric cycloadducts with four contiguous asymmetric carbons in an overall high chemical yield with excellent regioselectivity and diastereoselectivity. X-Ray single-crystal structure analyses revealed, with no doubt, the success of the synthesis of the target compounds. The 32CA reaction of AY 5b with ferrocene ethylene 1 has been studied within MEDT. This 32CA reaction proceeds via a two-stage one-step mechanism involving a high asyn…
N-Heterocyclic Carbene Catalyzed Asymmetric Synthesis of Pentacyclic Spirooxindoles via [3+3] Annulations of Isatin-Derived Enals and Cyclic N-Sulfon…
2019
A convenient enantioselective route to new types of pentacyclic spirooxindoles via [3+3] annulation reactions of isatin-derived enals and cyclic N-sulfonyl ketimines, using N-heterocyclic carbene (NHC) catalysis has been developed. The new protocol leads to pentacyclic spirooxindoles bearing a quaternary spirostereocenter in good yields and good to high enantiomeric ratios. peerReviewed
Multiplicity results for asymmetric boundary value problems with indefinite weights
2004
We prove existence and multiplicity of solutions, with prescribed nodal properties, to a boundary value problem of the formu″+f(t,u)=0,u(0)=u(T)=0. The nonlinearity is supposed to satisfy asymmetric, asymptotically linear assumptions involving indefinite weights. We first study some auxiliary half-linear, two-weighted problems for which an eigenvalue theory holds. Multiplicity is ensured by assumptions expressed in terms of weighted eigenvalues. The proof is developed in the framework of topological methods and is based on some relations between rotation numbers and weighted eigenvalues.
Leadership in internationalization strategies
2022
This paper examines leadership in internationalization strategies for an asymmetric cost duopoly where firms choose between exports and foreign direct investment (FDI) in a sequential setting. The incentive to lead and to engage in FDI is stronger for the more efficient firm. With sequential choices and the efficient firm playing in advance, it is less likely that firms pick identical internationalization strategies in equilibrium, as compared with simultaneous choices; this is more so for greater cost asymmetry. It also happens for large enough oligopoly profitability when the inefficient firm plays in advance. Follow-the-leader behaviour in FDI arises for low values of the setup cost. Alt…
Data from: The "unguarded-X" and the genetic architecture of lifespan: Inbreeding results in a potentially maladaptive sex-specific reduction of fema…
2018
Sex differences in ageing and lifespan are ubiquitous in nature. The "unguarded-X” hypothesis (UXh) suggests they may be partly due to the expression of recessive mutations in the hemizygous sex chromosomes of the heterogametic sex, which could help explain sex-specific ageing in a broad array of taxa. A prediction central to the UX hypothesis is that inbreeding will decrease the lifespan of the homogametic sex more than the heterogametic sex, because only in the former does inbreeding increase the expression of recessive deleterious mutations. In this study, we test this prediction by examining the effects of inbreeding on the lifespan and fitness of male and female Drosophila melanogaster…
0134 : Atrial fibrillation is associated with a marker of endothelial function and oxidative stress in patients with acute myocardial infarction
2016
Background Atrial fibrillation (AF), whether silent or symptomatic, is a frequent and severe complication of acute myocardial infarction (AMI). Asymmetric dimethylarginine (ADMA), an endogenous eNOS inhibitor, is a risk factor for endothelial dysfunction. We addressed the relationship between ADMA plasma levels and AF occurrence in AMI. Methods 273 patients hospitalized for AMI were included. Continuous electrocardiographic monitoring (CEM) e48 hours was recorded and ADMA was measured by High Performance Liquid Chromatography on admission blood sample. Results The incidence of silent and symptomatic AF was 39(14%) and 29 (11%), respectively. AF patients were markedly older than patients wit…
0127: Atrial fibrillation is associated with a marker of endothelial function and oxidative stress in patients with acute myocardial infarction
2016
Background Atrial fibrillation (AF), whether silent or symptomatic, is a frequent and severe complication of acute myocardial infarction (AMI). Asymmetric dimethylarginine (ADMA), an endogenous eNOS inhibitor, is a risk factor for endothelial dysfunction. We addressed the relationship between ADMA plasma levels and AF occurrence in AMI. Methods 273 patients hospitalized for AMI were included. Continuous electrocardiographic monitoring (CEM) ≥48 hours was recorded and ADMA was measured by High Performance Liquid Chromatography on admission blood sample. Results The incidence of silent and symptomatic AF was 39(14%) and 29 (11%), respectively. AF patients were markedly older than patients wit…
New insights into symptomatic or silent atrial fibrillation complicating acute myocardial infarction
2015
International audience; Atrial fibrillation (AF) is the most frequent heart rhythm disorder in the general population and contributes not only to a major deterioration in quality of life but also to an increase in cardiovascular morbimortality. The onset of AF in the acute phase of myocardial infarction (MI) is a major event that can jeopardize the prognosis of patients in the short-, medium- and long-term, and is a powerful predictor of a poor prognosis after MI. The suspected mechanism underlying the excess mortality is the drop in coronary flow linked to the acceleration and arrhythmic nature of the left ventricular contractions, which reduce the left ventricular ejection fraction. The p…
Symmetric dimethylarginine serum level as a new marker of left ventricular ejection fraction in patients with acute myocardial infarction
2013
Purpose: Asymmetric dimethylarginine (ADMA) is a by-product of protein methylation that has been implicated in the prognosis after acute myocardial infarction (MI) and heart failure through Nitric Oxide Synthase (NOS) inhibition. We aimed to investigate whether SDMA – the endogenous symmetrical stereoisomer of ADMA- that has insignificant inhibitory effects on NOS- might be a marker of left ventricular function in acute MI. Methods: Blood samples from 635 consecutive patients hospitalized 1 (23%). Mean LVEF was 55±13%. Mean ADMA, SDMA and L-arg levels were at 0.72±0.42, 0.51±0.44 and 91±54 μmol/L, respectively. Spearman analysis showed that LVEF was correlated negatively with SDMA (r=-0.151…