Search results for "stereochemistry"
showing 10 items of 4831 documents
The chemistry of [1,2,3]triazolo[1,5- c ]pyrimidine
2001
Abstract Reactions of [1,2,3]triazolo[1,5-c]pyrimidine 2 with some electrophiles and nucleophiles are reported. Triazole ring opening and loss of nitrogen is the principal reaction with electrophiles. With strong acids protonation on N6 competes successfully. Derivatives in which the pyrimidine ring has been opened are obtained in reactions with nucleophiles. No stable simple substitution compounds were found.
Aza-Henry Reaction of Isatin Ketimines with Methyl 4-Nitrobutyrate en Route to Spiro[piperidine-3,3′-oxindoles]
2015
A new enantioselective route to spiro[piperidine-3,3′-oxindoles] from isatin ketimines is described. The aza-Henry reaction of N-Boc-isatin ketimines with methyl 4-nitrobutyrate in the presence of a Ph2BOX-CuBr2 complex provided the corresponding nitro amino esters with good diastereoselectivity and excellent enantioselectivity (up to >99% ee). The aza-Henry adducts were transformed into spiro[piperidine-3,3′-oxindoles] after reduction of the nitro group to oxime, and cleavage of the N-Boc group and lactamisation.
Oligopeptide der β-Carbolin-3-carbonsäure - Synthese und Affinität zu Benzodiazepinrezeptoren
1987
Es wurden Oligopeptide der β-Carbolin-3-carbonsaure dargestellt und deren Affinitat zum Benzodiazepinrezeptor in Mausehirn-Membranen bestimmt. Uber Struktur-Affinitatsbeziehungen wird berichtet. Oligopeptides of β-Carboline-3-carboxylic Acid - Synthesis and Benzodiazepine Receptor Affinity Oligopeptides of β-carboline-3-carboxylic acid were prepared and tested with respect to their affinity for the benzodiazepine receptor in mouse brain membranes. Structure-affinity relationships are reported.
New Sesquiterpene Lactones and Other Constituents fromCentaurea paui
1997
Aerial parts of Centaurea paui afforded, in addition to several known sesquiterpene lactones, the two new elemanolides 2–4, the new elemane derivative 5 as well as the five new heliangolides 14–18. Their structures were elucidated by spectroscopic methods, especially high-field NMR spectroscopy. The structure of the heliangolide 12 previously isolated from this plant, has been confirmed by X-ray diffraction.
Structurally diverse second-generation [2.2]paracyclophane ketimines with planar and central chirality: syntheses, structural determination, and eval…
2005
A set of 20 novel [2.2]paracyclophane ketimines with planar and central chirality has been synthesized from enantiomerically pure and racemic 5-acyl-4-hydroxy[2.2]paracyclophane and alpha-branched chiral amines. Their X-ray structures were determined to elucidate the three-dimensional structures and the absolute configuration. The ketimines were used as catalysts in the asymmetric 1,2-addition reactions of diethylzinc with substituted benzaldehydes to furnish chiral alcohols in up to 95 % ee.
An Unexpected Three-Component Condensation Leading to Amino(3-oxo-2,3-dihydro-1H-isoindol-1-ylidene)acetonitriles.
2005
The reaction of 2-carboxybenzaldehyde with primary amines in the presence of cyanide leads to the formation of 2-substituted amino(3-oxo-2,3-dihydro-1H-isoindol-1-ylidene)acetonitriles. These compounds originate from the condensation of 2-carboxybenzaldehyde with the amine and two molecules of hydrogen cyanide and represent a novel class of isoindolinones.
Studies on the UV-photolytic decomposition of some tensides and complexones inhibiting the inverse-voltammetric determination of metal ions
1993
The UV-photolytic decomposition of some tensides and complexones has been investigated using the DPASV peak of indium as an indicator. The results show that UV-irradiation alone can completely decompose these compounds at lower concentrations within a short time. Higher concentrations need an additional oxidising agent.
Pyrazolo[3,4‐d]pyrimidine Derivatives as COX‐2 Selective Inhibitors: Synthesis and Molecular Modelling Studies
2009
The pyrazolo[3,4-d]pyrimidine system shows a multitude of interesting pharmacological properties. Owing to the potential anti-inflammatory activity of 5-benzamido-pyrazolo[3,4-d]pyrimidin-4-one derivatives and considering the easy synthesis of this class of compounds, a set of new 5-benzamido-1H-pyrazolo[3,4-d]pyrimidin-4-ones has been prepared in 42-80% yields by reacting 5-aminopyrazole-4(N-benzoyl)carbohydrazide derivatives and the opportune triethylorthoesters. Compounds 8a, b, 10a-d, and 11a, b revealed a superior inhibitory profile against COX-2, when compared to that of reference standards NS398 and indomethacin. Molecular modelling studies confirmed the obtained biological results.
Herbizide, 1. Mitt. 2-(4-Nitroanilino)pyrimidine
1982
Aus der Kondensation von 4-Nitrophenylguanidin (1) mit den β-Diketonen 2a–h gehen die 2-(4-Nitroanilino)pyrimidine 3a–h hervor. Als Aminoheterocyclus steht Verbindungstyp 3 in enger struktureller Beziehung zu 5-Acetyl-2-amino-4-methylthiazol, das herbizide Wirkungen auszuuben vermag. Herbicides, I: 2-(4-Nitroanilino)pyrimidines Condensation of 4-nitrophenylguanidine (1) with the β-diketones 2a–h yields the 2-(4-nitroanilino)pyrimidines 3a–h. Compounds of type 3 are aminoheterocycles and as such are closely related to 5-acetyl-2-amino-4-methylthiazole which exhibits herbicidal activity.
Trichomonazide Wirkstoffe, 2. Mitt. Verzweigtkettig 4,6-disubstituierte 2-Cyanaminopyrimidine
1985
Aus der Umsetzung von Dicyandiamid (1) mit den β-Diketonen 2a–b gehen die 4,6-verzweigtkettig disubstituierten 2-Cyanaminopyrimidine 3a–b hervor. Fur Strukturtyp 3 last sich aus den spektroskopischen Daten, speziell aus den 1H- und 13C-NMR-Werten, das Vorliegen eines Gleichgewichts zwischen den tautomeren 2-Cyanamino- und 2-Cyaniminopyrimidinformen ableiten. 3 zeichnet sich durch trichomonazide, antivirale und antimykotische Wirkung aus. Trichomonacidal Agents, II: 4,6-Disubstituted 2-(Cyanoamino)pyrimidines Carrying Branched Substituents The reaction of dicyandiamide (1) with the β-diketones 2a–b yields the 4,6-branched disubstituted 2-(cyanoamino)pyrimidines 3a–b. From spectroscopic evide…