Search results for "acids"

Tricks and Tracks in the Identification and Quantification of Endocannabinoids

2013

Abstract The endocannabinoid system serves pivotal roles in a diverse range of physiological and pathophysiological states, including behavior, pain, schizophrenia, obesity, Alzheimer disease, multiple sclerosis and cardiovascular disease. A number of endocannabinoids (eCBs) and their receptors have been characterised and identified in a plethora of biological matrices. The eCBs include N-arachidonoyl ethanolamine (anandamide), 2-arachidonoyl glycerol, 2-arachidonoyl glyceryl ether (noladin ether), O-arachidonoyl ethanolamine (virodhamine) and N-arachidonoyl dopamine. Advanced targeted mass spectrometry methods, particularly the selected reaction monitoring, has facilitated sensitive quanti…

Why Do Five-Membered Heterocyclic Compounds Sometimes Not Participate in Polar Diels–Alder Reactions?

2013

The reactions of bicyclic enone (BCE, 1) with cyclopentadiene (Cp, 2) and the five-membered heterocyclic compounds (FHCs) furan 3 and N-methyl pyrrole 4 for the construction of polycyclic heterocyclic compounds have been studied at the B3LYP/6-31G* level. No reaction takes place in the absence of Lewis acid (LA) catalysts as a consequence of the high activation energy associated with these reactions. Electrophilic activation of BCE 1 by formation of a complex with the BF3 LA, 1-BF3, and solvent effects favor the reactions. However, a different reactivity is manifested by Cp 2 and FHCs 3 and 4. Thus, while the reaction of 1-BF3 with Cp 2 yields the expected exo [4 + 2] cycloadduct, the react…

Phorbol Esters and Muscarinic Receptor Agonists Activate Phospholipase D in Heart and Brain

1991

Phospholipase D (PLD) hydrolyzes phosphatidylcholine and thereby seems to play a key role in a novel pathway of signal transduction. PLD activity in rat hippocampal slices and atria of rat, guinea pig and chicken hearts was determined by measuring the catalytic products choline (Ch), phosphatidic acid (PA) and, in the presence of a primary alcohol, phosphatidylpropanol or phosphatidylethanol. It was found that the PLD activity was high, even under resting conditions, in both tissues, especially in the hippocampus, and that the enzyme activity could be enhanced by activation of protein kinase C and by muscarinic receptor stimulation.

ChemInform Abstract: Low-Loading Asymmetric Organocatalysis

2012

Asymmetric organocatalysis is now recognized as the third pillar of asymmetric synthesis. Recent years have witnessed increasing interest towards the use of highly active and stereoselective organocatalysts. This critical review documents the advances in the development of chiral organocatalysts which are systematically used in ≤3 mol% loading in all the sub-areas of the field, namely aminocatalysis, Bronsted acids and bases, Lewis acids and bases, hydrogen bond-mediated catalysis, phase transfer and N-heterocyclic carbene catalyses (194 references).

Surfactant-assisted chromogenic sensing of cyanide in water

2009

Chromogenic cyanide recognition in water was achieved by the use of a hydrophobic dye in micellar containers.

Kronenether mit einem Lewis-sauren Zentrum, eine neue Klasse heterotoper Wirtmoleküle

1991

Aminosäureester als chirale Hilfsgruppen in Lewis-Säure-katalysierten Umsetzungen elektronenreicher Siloxydiene mit Iminen

1990

ChemInform Abstract: Reversal of Asymmetric Induction in Stereoselective Strecker Synthesis on Galactosyl Amine as the Chiral Matrix.

1989

Abstract The reversal of the direction of asymmetric induction in Lewis acid catalyzed Strecker synthesis using the 2,3,4,6-tetra-O-pivaloyl-β-D-galactopyranosyl amine 1 is described. In isopropanol or tetrahydrofuran 1 had given ( R )-diastereomers of the corresponding α-amino nitriles preferably. However, in chloroform in the presence of heterogeneous zinc chloride the same auxiliary alternatively leads to an excess of the ( S )-diastereomers.

Nickel as a Lewis Base in a T‐Shaped Nickel(0) Germylene Complex Incorporating a Flexible Bis(NHC) Ligand

2018

Flexible, chelating bis(NHC) ligand 2, able to accommodate both cis- and trans-coordination modes, was used to synthesize (2)Ni(η 2 -cod), 3. In reaction with GeCl2, this produced (2)NiGeCl2, 4, featuring a T-shaped Ni(0) and a pyramidal Ge center. Complex 4 could also be prepared from [(2)GeCl]Cl, 5, and Ni(cod)2, in a reaction that formally involved Ni-Ge transmetalation, followed by coordination of the extruded GeCl2 moiety to Ni. A computational analysis showed that 4 possesses considerable multiconfigurational character and the Ni→Ge bond is formed through σ-donation from the Ni 4s, 4p, and 3d orbitals to Ge. (NHC)2Ni(cod) complexes 9 and 10, as well as (NHC)2GeCl2 derivative 11, incor…

The Aluminyl Anion : A New Generation of Aluminium Nucleophile

2020

Trivalent aluminium compounds are well known for their reactivity as Lewis acids/electrophiles, a feature that is exploited in many pharmaceutical, industrial and laboratory-based reactions. Recently, a series of isolable aluminium(I) anions ('aluminyls') have been reported, which offer an alternative to this textbook description: these reagents behave as aluminium nucleophiles. This minireview covers the synthesis, structure and reactivity of aluminyl species reported to date, together with their associated metal complexes. The frontier orbitals of each of these species have been investigated using a common methodology to allow for a like-for-like comparison of their electronic structure a…