Search results for "ALK"

Alkali metal complexation properties of resorcinarene bis-crown ethers: effect of the crown ether functionality and preorganization on complexation

2008

Abstract The synthesis and characterization of tetramethoxy resorcinarene tribenzo-bis-crown ethers, m - and p -TBBC6 , are described. The effect of the added aromatic functionality in the crown ether bridge on the alkali metal complexation properties was investigated and compared to the properties of tetramethoxy resorcinarene bis-crown-5 ( BC5 ) by means of 1 H NMR spectroscopy and X-ray crystallography. It was found that BC5 and m -TBBC6 were capable of binding alkali metal cations (K + , Rb + , and Cs + ), with the highest affinity toward Cs + cation, while no binding was observed in the case of p -TBBC6 , which confirms the significance of the complementarity and preorganization for co…

Syntheses of novelN-([18F]fluoroalkyl)-N-nitroso-4-methyl-benzenesulfonamides and decomposition studies of corresponding19F- and bromo-analogues: pot…

2003

N-([ 18 F]fluoroalkyl)-N-nitroso-4-methyl-benzensulfonamides [n-alkyl = (-CH 2 ) [ 18,19 F]F, n=2-4)] were synthesized in radiochemical yields ranging from 75-90% to provide new secondary labelling precursors for the syntheses of 18 F-labelled compounds. Preliminary decomposition studies utilizing the corresponding non-radioactive 19 F-compounds as well as the bromo containing analogous compounds were performed to evaluate their stability regarding temperature and basicity of the labelling medium. Furthermore, initial difficulties in labelling these compounds led to the development of a modified labelling procedure applying nearly solvent-free conditions. Extensive decomposition experiments…

Conformational polymorphism and amphiphilic properties of resorcinarene octapodands

2010

o-Nitroaniline functionalized resorcinarene octapodands 1-5 with pendant methyl, ethyl, pentyl, nonyl or 1-decenyl groups, respectively, were synthesized and their structural properties investigated using X-ray crystallography and NMR spectroscopy. The upper rim of each podand is identical containing flexible side arms, in which rotation around the -OCH(2)CH(2)N- linkers create excellent possibilities for polymorphism. Two conformational polymorphs of acetone solvate of 2 were identified containing different side arm orientation and crystal packing. Compound 1 crystallized from acetone and nitromethane yielding two pseudopolymorphs with different packing motifs. The longer alkyl chains of 3…

Configuration of Enolates of β-Ketocarboxylic Acid Esters — Carbocation-Carbanion Salts

1996

Deprotonation of (Z)- or (E)-3-hydroxy-2,3-dimesitylpropenoic acid methyl ester (1a) with tetrakis(dimethylamino)-methane (3) led to stable salt (E)-2a, which belongs to a very rare species of salts that consist of a heteroatom-stabilized carbocation and a heteroatom-stabilized carbanion. An analogous guanidinium salt (E)-2b was formed in the reaction of 3-oxo-2,3-diphenylpropanoic acid methyl ester (1b) and 3. The molecular structures of these enolates were studied by NMR spectroscopy and an X-ray analysis of (E)-2a {MC[N(CH3)2]3} and compared with those of the corresponding alkali enolates.

1983

Introduction des groupes alkyl dans le polyamide commercial Trogamid T. Formation d'anions polyamides par l'hydrure de sodium puis alkylation par les bromures d'alkyle

Untersuchungen von polymeren im massenspektrometer, 3. Fragmentierungsreaktionen oligomerer benzyle

1974

Beim thermischen Abbau von Polybenzylen im Massenspektrometer werden oligomere Benzylbruchstucke mit gesattigten (Phenyl-, Alkyl-) und ungesattigten (Chinonmethid)-Endgruppen gebildet. Zur Differenzierung der thermischen und elektronenstosinduzierten Abbaureaktionen wurden die Fragmentierungsreaktionen oligomere Benzyle vom Typ 1a, b im Massenspektrometer untersucht. Bei Anwendung niedriger Elektronenstosenergien wurden als Hauptfragmentierungsreaktionen Alkyl-, α-Benzyl- und β-Benzylspaltung sowie die fur 1,2-disubstituierte Benzyle strukturspezifische ortho-Umalgerung gefunden, die eine Differenzierung stellungsisomerer Oligobenzyle ermoglicht. Die genannten Reaktionen wurden durch Hochau…

Homogeneous ethylene-polymerization catalysts based on alkyl cations of the rare-earth metals: are dicationic mono(alkyl) complexes the active specie…

2003

Copper(I)‐chitin biopolymer based: An efficient and recyclable catalyst for click azide–alkyne cycloaddition reactions in water

2021

Clicked and long spaced galactosyl- and lactosylcalix[4]arenes: New multivalent galectin-3 ligands

2014

Four novel calix[4]arene-based glycoclusters were synthesized by conjugating the saccharide units to the macrocyclic scaffold using the CuAAC reaction and using long and hydrophilic ethylene glycol spacers. Initially, two galactosylcalix[4]arenes were prepared starting from saccharide units and calixarene cores which differ in the relative dispositions of the alkyne and azido groups. Once the most convenient synthetic pathway was selected, two further lactosylcalix[4]arenes were obtained, one in the cone, the other one in the 1,3-alternate structure. Preliminary studies of the interactions of these novel glycocalixarenes with galectin-3 were carried out by using a lectin-functionalized chip…

Radiosynthesis of (±)-(2-((4-(2-[18F]fluoro-ethoxy)phenyl)bis(4-methoxy-phenyl)methoxy)ethylpiperidine-3-carboxylic acid: a potential GAT-3 PET ligan…

2001

A dysfunction of GABAergic neurotransmission is related to diseases such as epilepsy, Huntington-disease and Parkinson-syndrome. A new 18F-fluorine labelled GABA transporter ligand for the GABA-transporter subtype GAT-3 was developed which may allow the in vivo visualisation of GABAergic neurotransmission. The precursors ethyl (2-(4-hydroxyphenyl)bis(4-methoxyphenyl)-methoxy)ethyl)-piperidine-3-carboxylate and ethyl(2-((4-(2-tosylethoxy)phenyl)-bis(4-methoxyphenyl)-methoxy) ethyl)-piperidine3-carboxylate were synthesised and labelled by the use of 2-[18F]fluoroethyltosylate or [18F]fluoride. Subsequent cleavage of the ester moiety gave the final product (±)-(2-((4-(2-[18F]fluoroethoxy)pheny…