Home About us Contact
|
Home About us Contact | ||
|
|
||
Molecular Rearrangement (molecular + rearrangement)
Selected AbstractsSynthesis of Thienothiopyranthiones by a New Molecular Rearrangement.CHEMINFORM, Issue 29 2005Vladimir A. Ogurtsov Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Photoinduced Molecular Rearrangements.CHEMINFORM, Issue 43 20014-Oxadiazoles into , 4-Oxadiazoles., Some Comments on the Ring-Photoisomerization of Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis of 3-Aminotropones from N -Boc-Protected Furan-2-amine (=tert -Butyl Furan-2-ylcarbamate; Boc=(tert -Butoxy)carbonyl) by Cycloaddition Reactions and Subsequent RearrangementHELVETICA CHIMICA ACTA, Issue 2 2008Ángel Abstract The 3-aminotropones (=3-aminocyclohepta-2,4,6-trien-1-ones) 4 were prepared in two steps by i) a [4+3] cycloaddition reaction between a conveniently substituted ,,,,-dihalo ketone 1 and a furan-2-amine derivative 2 functionalized at C(2) by a protected amino group (,3), and ii) a base-induced molecular rearrangement of the cycloadduct 3via cleavage of the O-bridge. A mechanism for the formation of 3-aminotropones is proposed on the basis of the initial deprotonation of the [(tert -butoxy)carbonyl]amino (BocNH) group of 3, followed by O-bridge opening, an acid,base equilibrium, and finally an alkoxyaluminate elimination to afford the conjugated stable troponoid system (Scheme,7). [source] Preparation of 2-phenyl-2-hydroxymethyl-4-oxo-1,2,3,4-tetrahydroquinazoline and 2-methyl-4-oxo-3,4-dihydroquinazoline derivatives formation,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2000Pavel Hradil The cyclization of phenacyl anthranilate has been studied with the aim to develop the synthesis of 2-(2,-aminophenyl)-4-phenyloxazole. However, a different course of the reaction than expected was observed. 2-Phenyl-2-hydroxymethyl-4-oxo-1,2,3,4-tetrahydroquinazoline (3a) was formed by the reaction of phenacyl anthranilate (2) with ammonium acetate under various conditions. 3-Hydroxy-2-phenyl-4(1H)-quinolinone (4) arose by heating compound 3a in acetic acid. The same compound was obtained by melting compound 3a, but the yield was lower. Different types of products resulted in the reaction of compound 3a with acetic anhydride. Under mild conditions acetylated products 2-acetoxymethyl-2-phenyl-4-oxo-1,2,3,4-tetrahydroquinazoline (7a) and 2-acetoxymethyl-3-acetyl-2-phenyl-4-oxo-1,2,3,4-tetrahydroquinazoline (8) were prepared. If the reaction was carried out under reflux of the reaction mixture, molecular rearrangement took place to give cis and trans 2-methyl-4-oxo-3-(1-phenyl-2-acetoxy)vinyl-3,4-dihydroquinazolines (9a and 9b). All prepared compounds have been characterised by their 1H, 13C and 15N NMR spectra, IR spectra and MS. [source] Soil moisture stress-induced alterations in bioconstituents determining tea qualityJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2003PR Jeyaramraja Abstract The impact of water stress on the biochemical constituents that determine black tea quality was investigated. Phenylalanine ammonia lyase (PAL) activity was highest in the drought tolerant ,Assam' cultivar UPASI-2, followed by UPASI-8 and UPASI-9, under non-stress conditions. Under soil moisture stress a reduction in PAL activity was found in all three clones investigated. A strong positive correlation was observed between an increase in soil moisture deficit and a decrease in PAL activity. Lower PAL activity correlated well with lower synthesis of flavanols such as epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), which are important precursors of theaflavin-3,3,-digallate that determines final tea quality. Altered synthesis of EGCG and ECG could be due to their molecular rearrangement at elevated leaf temperature during drought. Synthesis of quality constituents such as gallic acid and caffeine declined significantly owing to both drought and waterlogging stress. The reduction in gallic acid due to water stress could lead to lower synthesis of theaflavin fractions such as epitheaflavic acid, epitheaflavic acid-3,-gallate and theaflavic acid and, thereby, quality deterioration. Similarly to drought, flooding stress was also found to alter the biochemical constituents necessary for tea quality. Copyright © 2003 Society of Chemical Industry [source] Excitatory amino acid transporters EAAT-1 and EAAT-2 in temporal lobe and hippocampus in intractable temporal lobe epilepsyAPMIS, Issue 4 2009SINAN SARAC Intractable temporal lobe epilepsy (TLE) is an invalidating disease and many patients are resistant to medical treatment. Increased glutamate concentration has been found in epileptogenic foci and may induce local over-excitation and cytotoxicity; one of the proposed mechanisms involves reduced extra-cellular clearance of glutamate by excitatory amino acid transporters (EAAT-1 to EAAT-5). EAAT-1 and EAAT-2 are mainly expressed on astroglial cells for the reuptake of glutamate from the extra-cellular space. We have studied the expression of EAAT-1 and EAAT-2 in the hippocampus and temporal lobe in 12 patients with TLE by immunhistochemistry and densitometry. The expression of EAAT-1 and EAAT-2 was reduced to approximately 40% and 25%, respectively, in CA1 of the hippocampus. In the same area, an increased expression of glial fibrillary acid protein (GFAP) at 90% reflected molecular rearrangements and upregulation of GFAP in the existing astrocytes as Ki-67 staining failed to demonstrate any signs of astrocytic proliferation. The aetiology of the reduced expression of EAAT-1 and EAAT-2 remains unclear. The downregulation of EAAT-1 and EAAT-2 may be an adaptive response to neuronal death or it may be a causative event contributing to neuronal death. Further studies of the EAATs and their function are needed to clarify the mechanisms and significance of EAAT-1 and EAAT-2 disappearance in TLE. [source] | ||||||||||