Search results for "Isomer"

The influence of fluorine position on the properties of fluorobenzoxaboroles

2015

5-Fluoro-2,1-benzoxaborol-1(3H)-ol, a potent antifungal drug also known as Tavaborole or AN2690, has been compared with its three isomers in terms of its activity against several fungi as well as pKa and multinuclear NMR characterization. The molecular and crystal structure of 6-fluoro-2,1-benzoxaborol-1(3H)-ol was determined and compared with that of AN2690.

An Efficient Synthesis of γ-Aminoacids and Attempts to Drive Its Enantioselectivity

2008

Addition of carboxylic acid dianions to bromoacetonitrile lead, in good yields,to the corresponding gamma-cyanoacids, which on hydrogenation yielded gamma-amino acids. This two step methodology improves upon previously described results. Poor e.e's resultedfrom our attempts to drive the enantioselectivity of this transformation by chiral amide induction.

Biotransformation in vitro of the 22R and 22S epimers of budesonide by human liver, bronchus, colonic mucosa and skin.

2001

The pharmacological effects of glucocorticoids are greatly influenced by their pharmacokinetic properties. In the present report, the in vitro biotransformation of the 22R and 22S epimers of the topical steroid budesonide was studied in the S-9 fraction of human liver, bronchus, skin and colonic mucosa. The disappearance of unchanged epimers of budesonide was measured during 90 min of incubation by high performance liquid chromatography. The rate of disappearance was high in human liver while little biotransformation occurred in bronchial tissue and colonic mucosa, and none was detected in the skin. A marked decay of the initial concentration of unchanged budesonide epimers was noticed afte…

Tuning Azoheteroarene Photoswitch Performance through Heteroaryl Design

2017

International audience; Photoswitchable compounds, which can be reversibly switched between two isomers by light, continue to attract significant attention for a wide array of applications. Azoheteroarenes represent a relatively new but understudied type of photoswitch, where one of the aryl rings from the conventional azobenzene class has been replaced with a five-membered heteroaromatic ring. Initial studies have suggested the azoheteroarenes – the arylazopyrazoles in particular – to have excellent photoswitching properties (quantitative switching and long Z isomer half-life). Here we present a systematic computational and experimental study to elucidate the origin of the long thermal hal…

Tetrazola hemiamināls kā hirāla palīggrupa

2017

Tetrazola hemiamināls kā hirāla palīggrupa. Sējējs M., zinātniskais vadītājs Prof., Dr. chem. Sūna E., konsultēja MSc. chem., Kinēns A. Maģistra darbs uzrakstīts latviešu valodā, tā apjoms 58 lapaspuses. Darbs satur 56 attēlus, 5 tabulas. Maģistra darbs veltīts terazolu hemiaminālu hirālās palīggrupas iegūšanai un pielietojumam diastereoselektīvajā sintēzē. Izstrādātās hirālās palīggrupas efektivitāte demonstrēta, ar augstu diastereoselektivitāti veicot karbonskābju α-pozīcijas fluorēšanas un nitrozo-aldola reakcijas. Darba rezultātā izstrādāts tetrazola hemiamināla hirālās palīggrupas stereoindukcijas modelis. Demonstrēta hirālās palīggrupas šķelšana maigos reakcijas apstākļos. Tetrazola h…

Molecular orbital studies on the mechanism of catalytic isomerization of xylenes II. The photochemical process

1981

Abstract The feasibility of an intermediate step in the mechanism of photochemical isomerization of xylenes in acidic media is explored by using CNDO molecular orbital methods. Along the reaction path from 2,6-dimethylbenzenium ion to dimethylbicyclo[3.1.0]hexenyl cation, the energy surfaces for this intermediate step have been drawn both for the first singlet S1 and triplet T1 excited states. The energies of these excited states have been calculated by adding to the ground-state energy calculated by CNDO/2 method the excitation energy calculated by CNDO/S-CI method. An optimization of the saddle point energy is achieved by introducing the angle between methyl groups and the ring plane as a…

Fast evaluation of enantioselective drug metabolism by electrophoretically mediated microanalysis: application to fluoxetine metabolism by CYP2D6.

2013

In this work, a capillary electrophoretic methodology for the enantioselective in vitro evaluation of drugs metabolism is applied to the evaluation of fluoxetine (FLX) metabolism by cytochrome 2D6 (CYP2D6). This methodology comprises the in-capillary enzymatic reaction and the chiral separation of FLX and its major metabolite, norfluoxetine enantiomers employing highly sulfated β-CD and the partial filling technique. The methodology employed in this work is a fast way to obtain a first approach of the enantioselective in vitro metabolism of racemic drugs, with the additional advantage of an extremely low consumption of enzymes, CDs and all the reagents involved in the process. Michaelis-Men…

On the Photoisomerization of Caffeic Acid in the Presence of Nanostructured TiO2

2014

Lower rim arylation of calix[n]arenes with extended perfluorinated domains

2006

Abstract Exhaustive O-arylation of p-tert -butylcalix[ n ]arenes 2 ( n  = 4–8) with an excess of 3-pentadecafluoroheptyl-5-pentafluorophenyl-1,2,4-oxadiazole 3 and K 2 CO 3 in refluxing acetonitrile provides an easy entry to a new family of perfluorinated calix[ n ]arenes 1 . The cyclic tetramer furnishes a mixture of cone , partial cone , and 1,2-alternate conformers, while the larger macrocycles afford single products. The structures of all new compounds are substantiated by NMR techniques and MALDI-TOF mass spectral data. Single-crystal X-ray diffraction studies on the pentamer derivative 1b reveal a distorted cone-in conformation of the calixarene cup.

Malignant transformation of the liver tumour precursor cell line OC/CDE 22 by the four stereoisomeric fjord region 3,4-dihydrodiol 1,2-epoxides of be…

1995

In previous work we established the rat liver oval cell line OC/CDE 22 in order to study in vitro mechanisms of liver cell transformation. We have now exposed OC/CDE 22 cells to each of the four optically active fjord region dihydrodiol epoxides of benzo[c]phenanthrene to investigate their capacity for malignant transformation of liver cells. All four configurational isomers, which are among the most potent carcinogenic metabolites of polycyclic aromatic hydrocarbons tested in murine tumour models, malignantly transform OC/CDE 22 cells at a 2 microM dose level, resulting in a similar colony-forming efficiency in soft agar. Inoculation of the transformed cells into newborn syngeneic rats pro…