Search results for "SoMe"
showing 10 items of 5114 documents
Stereoselective Synthesis of 8,12-Furanoeudesmanes from Santonin. Absolute Stereochemistry of Natural Furanoeudesma-1,3-diene and Tubipofurane.
1996
Ketobutenolide 3, easily obtained from santonin (1), has been transformed into two natural furanoeudesmanes 4 and 5, isolated from Commiphora molmol and Tubipora musica, respectively. trans- And cis-decalin systems were obtained by stereoselective reduction of the C(4)-C(5) double bond in 3 in the following way: hydrogenation of 3 over Pd/C followed by acidic treatment gave the cis isomer 10 as the major product; selective hydrogenation of the C(1)-C(2) double bond with the Wilkinson's catalyst followed by reduction with NaTeH yielded mainly the trans isomer 9. Compounds 9 and 10 were transformed into 4 and 5 in parallel sequences. Optical rotation and CD measurements of the synthetic produ…
Measurement of Protein Synthesis: In Vitro Comparison of 68Ga-DOTA-Puromycin, [3H]Tyrosine, and 2-Fluoro-[3H]tyrosine
2012
Aim: Puromycin has played an important role in our understanding of the eukaryotic ribosome and protein synthesis. It has been known for more than 40 years that this antibiotic is a universal protein synthesis inhibitor that acts as a structural analog of an aminoacyl-transfer RNA (aa-tRNA) in eukaryotic ribosomes. Due to the role of enzymes and their synthesis in situations of need (DNA damage, e.g., after chemo- or radiation therapy), determination of protein synthesis is important for control of antitumor therapy, to enhance long-term survival of tumor patients, and to minimize side-effects of therapy. Multiple attempts to reach this goal have been made through the last decades, mostly u…
ChemInform Abstract: Advances in Indolo[2,3-a]carbazole Chemistry: Design and Synthesis of Protein Kinase C and Topoisomerase I Inhibitors
2010
Indolo[2,3-a]carbazoles, their pyrrolo[3,4-c]anellated variants and structurally closely related bisindolylmaleimides represent a biologically highly interesting class of natural compounds which are potential anticancer agents. According to the ongoing literature new and efficient synthetic methods yield a great variety of these compounds which have been reported in detail. The biological activities and the inhibitory activities against the target enzymes protein kinase C and topoisomerase I are also discussed including structure activity relationships. A molecular binding model of the protein kinase C inhibitors with the target enzyme at the atomic level is presented and supported by X-ray…
Synthese von Benzo[b]thioxanthenen
1995
Synthesis of Benzo[b]thioxanthenes Benzo[b]thioxanthenes, heterocyclic compounds related to tetracenes and tetracyclines can be obtained by the reaction of 2H-benzo[b]thiete (1) and 1,4-naphthoquinones (3a–g). The primary cycloadducts 4a–g undergo an autoxidation process leading to the quinones 6a–g. The dihydroxy compound 4e shows an additional isomerization by a tetrafold H transfer (4e 5e′). Another preparative route to benzo[b]thioxanthenes makes use of the cycloadditon reaction of 1 and 1,4-epoxynaphthalenes (7a–d). The primary adducts can be transformed to the title compounds by catalytic dehydration processes (8a–d 9a-d). An alternate regioselective opening of the oxygen bridge can b…
ChemInform Abstract: Photoinduced Molecular Rearrangements. Some Comments on the Ring-Photoisomerization of 1,2,4-Oxadiazoles into 1,3,4-Oxadiazoles.
2010
The ring-photoisomerization of 3-amino- and 3-methylamino-5-phenyl-1,2,4-oxadiazoles into the corresponding 2-amino- and 2-methylamino-5-phenyl-1,3,4-oxadiazoles has been reinvestigated by examining the effect of a base on the photoreaction. On irradiating at λ = 254 nm in methanol, yields of the ring-photoisomers were found to be significantly enhanced by the addition of triethylamine (TEA) in the photoreaction medium. By contrast, irradiation of the 3-amino-5-phenyloxadiazole in acetonitrile containing TEA gave an almost complete photoreduction into benzoylguanidine, while few percent of the ring photoisomer were detected. Furthermore, the pyrene-sensitized photolysis of 3-amino-5-phenylo…
Rearrangement of Germacranolides. Synthesis and Absolute Configuration of Elemane and Heliangolane Derivatives from Cnicin
2003
A study of the Cope rearrangement of 15-oxo-germacranolides to 15-oxo-elemanolides has been carried out. The synthesis of two natural elemanolides, isolated from Centaurea paui, and an efficent isomerization of the C-4/C-5 double bond of 15-oxo-germacranolides to form heliangolides are reported. The absolute configuration of all the compounds has been ascertained. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Mammalian Xenobiotic Epoxide Hydrolases
2002
ChemInform Abstract: Modified Photobehavior of Carboxylic Acid Derivatives Induced by Protonation.
1987
Abstract A series of carboxylic acid derivatives 1–6 containing a second interacting function have been converted into the corresponding O -protonated species or acylium ions upon treatment with 96% sulfuric acid or oleum, respectively, at room temperature. The resulting stable cations have been spectroscopically characterized and submitted to irradiation. Cis-trans photoisomerization was observed in the ionic speciesderived from trans -crotonic, fumaric and maleic acids, and maleic anhydride. By contrast protonated crotonolactone 5a+ was found to be photostable. Finally, protonated α-bromobutyrolactone 6a+ was clean and efficiently dehydrohalogenated to 5a+ upon irradiation. Since the norm…
Conformational studies of hexapeptides containing two dehydroamino acid residues in positions 3 and 5 in peptide chain
2008
Abstract Synthesis and structural studies of hexapeptides containing two dehydroamino acid residues in positions 3 and 5 in a peptide chain were performed. All the investigated peptides adopted bent conformations, stabilized by intramolecular hydrogen bonding, and could exist as two different conformers in solution. Only in the case of the peptide containing ΔAla residues, expected 3 10 -helical conformation was found.
Crystal structure of diethyl (E)-2-[(benzofuran-2-yl)methylidene]succinate
2015
The title compound, C17H18O5, was synthesized by a base-free catalytic Wittig reaction. The molecule consists of a diethyl itaconate unit, which is connectedviathe C=C double bond to a benzofuran moiety. The benzofuran ring system (r.m.s. deviation = 0.007 Å) forms dihedral angles of 79.58 (4) and 12.12 (10)° with the mean planes through thecisandtransethoxycarbonyl groups, respectively. An intramolecular C—H...O hydrogen bond involving the O atom of the benzofuran moiety is observed. In the crystal, molecules are linked into ribbons running parallel to thebaxis by C—H...O hydrogen bonds.