Search results for "stereochemistry"
showing 10 items of 4831 documents
ChemInform Abstract: Synthesis of Pyrido[2,1-a]isoquinolin-4-ones and Oxazino[2,3-a]isoquinolin-4-ones: New Inhibitors of Mitochondrial Respiratory C…
2014
Benzo[a]quinolizine is an important heterocyclic framework that can be found in numerous bioactive compounds. The general scheme for the synthesis of these compounds was based on the preparation of the appropriate dihydroisoquinolines by Bischler-Napieralski cyclization with good yields, followed by the Pemberton method to form the oxazinones or pyridones derivatives via acyl-ketene imine cyclocondensation. All the synthesized compounds were assayed in vitro for their ability to inhibit mitochondrial respiratory chain. Most of the tested compounds were able to inhibit the integrated electron transfer chain, measured as NADH oxidation, which includes complexes I, III and IV, in the low micro…
4-[5-(4-Fluorophenyl)-3-isopropylisoxazol-4-yl]pyridine
2006
In the title compound, C17H15FN2O, the exocyclic bond angles at the C atoms of the isoxazole ring bearing the pyridyl and 4-fluorophenyl substituents are 129.66 (17) and 134.58 (16)°, respectively. The structure was determined in a study of the molecular geometry of isoxazole derivatives with biological activity as MAPK inhibitors.
Synthesis and pharmacological activity of silyl isoxazolines 2
2003
Silyl isoxazolines have been synthesized by [2+3] cycloaddition reaction of nitrile oxides to vinyl- and allylsilanes. The addition of 3-pyridylnitrile oxide to 1,3-divinyl-1,1,3,3-tetraphenyldisiloxane affords 1,3-bis{5-[3-(3-pyridyl)isoxazolin-2-yl]}-1,1,3,3-tetraphenyldisiloxane; the latter exists as a mixture of trans- and cis-isomers.The bond angle of the Si–O–Si fragment in thetrans-isomer equals 180(3)° and in the cis-isomer it is 162(3)°.The pharmacological properties of 4-[3-(5-trimethylsilylisoxazolin-2-yl)]pyridinium-chloride have been studied.
New Synthesis oftrans-Disubstituted Cyclam Macrocycles – Elucidation of the Disubstitution Mechanism on the Basis of X-ray Data and Molecular Modeling
1998
A new way to synthesize trans-disubstituted cyclam tetraazamacrocycles 1 is reported. The synthesis proceeds in three steps via the tricyclic 1,4,8,11-tetraazatricyclo[9.3.1.14,8]hexadecane system 2, which can be selectively dialkylated and hydrolyzed under basic conditions to give the final product 1. An understanding of the reactivity, based on the X-ray experimental electrostatic potential and molecular modeling of the 1,4,8,11-tetraazatricyclo[9.3.1.14,8]hexadecane macrotricycle, has permitted the elucidation of a new reaction pathway leading to the trans-disubstituted cyclam.
Cardopatine and isocardopatine, two novel cyclobutane substances from Cardopatium corymbosum
1978
Two new natural substances containing a cyclobutane unit, cardopatine and isocardopatine, the trans and cis isomers respectively of 5,5″ (cyclobut-1,2-ylene-diethynylene)bis 2,2′-bithiophene), together with the known α-terthienyl and 5-(but-3-en-1-ynyl)-2,2′-bithienyl, have been isolated from the roots of Cardopatium corymbosum. Evidence is given that the novel cyclobutane substances are not the products of a spontaneous dimerization of a bithienyl monomeric unit. Structure determination and conformational analysis are reported.
Influence of synthesis conditions on the morphology of Dodecasil 1H
1993
Abstract The synthesis of Dodecasil 1H was studied in the system SiO2/1-adamantylamin/NH3/water with the objective of controlling the particle size and the morphology of the crystals. Since nucleation occurs in a very early stage of the synthesis, the heating rate to the final temperature and/or holding points during heat up have a strong influence on both parameters. Crystals smaller than 150 μm could only be obtained by the use of seed crystals, which are completely consumed in the synthesis with subsequent new nucleation. Using seed crystals, the expensive template 1-adamantylamine can be substituted with cheaper reagents such as sodium dodecyl sulfate or trimethylethylammonium bromide a…
Regioselective Synthesis of 2-Imino-1,3-thiazolidin-4-ones by Treatment ofN-(Anthracen-9-yl)-N′-ethylthiourea with Bromoacetic Acid Derivatives
2002
The reaction between N-(anthracen-9-yl)-N′-ethylthiourea (1) and methyl bromoacetate yielded mainly 2-[(anthracen-9-yl)imino]-3-ethyl-1,3-thiazolidin-4-one (2), together with some of the regioisomeric 3-(anthracen-9-yl)-2-ethylimino-1,3-thiazolidin-4-one (3). The structures of the products were elucidated by NMR techniques and, for 3, X-ray crystallographic analysis. Treatment of 1 with bromoacetyl bromide again yielded 2 and 3, but with a reversed product distribution ratio, thus providing an interesting and unexpected regioselectivity, depending on the electrophile selected. The underlying cause of the observed regioselectivity is a result of different reaction pathways taken by the two e…
Herbizide, 8. Mitt. Herbicides, VIII. Kernchlorierte und -bromierte Anilinoethentricarbonitrile
1987
In einer Reihe von Herbiziden tritt als gemeinsames Strukturelement die Nitrilgruppe auf, wie in 2,6-Dichlorbenzonitril oder 4-Amino-2,3,5,6-tetrafluorbenzonitril. Als ein weiterer Vertreter dieser Strukturklasse ist in unseren jungsten Untersuchungen das 2-Cyanamino-4,6-diethylpyrimidin durch seine herbizide Wirksamkeit aufgefallen. In Fortfuhrung dieser Forschungsrichtung und in Anlehnung an Herbizide, in denen Kernhalogenierungen eine dominierende Rolle spielen, sind nunmehr entsprechende Partialstrukturen in unsere Untersuchungen einbezogen worden.
13C nuclear magnetic resonance spectra of several podocarpane and cassane diterpenoids
1990
The 13C NMR spectra of several diterpenic derivatives having the podocarpane and cassane skeleton were recorded and interpreted. The most significant effects due to substituent orientation, B/C ring junction stereochemistry and conformational changes are briefly discussed.
Antidiabetische wirkstoffe. V Lang- und verzweigtkettig substituierte chlor-dihexylamino-1,3,5-triazine
1985
Die nucleophile Substitution eines Chloratoms in 2,4-Dichlor-6-dihexylamino-1,3,5-triazin (1) durch Amine (2a-c) fuhrt zu den Alkylamino-chlor-dihexylamino-1,3,5-triazinen 3a-c. Fur Strukturtyp 3 typische Signale in den 1H-NMR-Spektren sind das Triplett bei 0,9 ppm fur die endstandigen Methylgruppen und das Multiplett bei 3,3-3,65 ppm fur die den Stickstoffatomen benachbarten Methylengruppen. In Verbindungsklasse 3 finden sich Vertreter mit antidiabetischer, trichomonazider, antiviraler und anthelminthischer Wirksamkeit. The nucleophilic substitution of one chlorine atom in 2,4-dichloro-6-dihexylamino-1,3,5-triazine (1) by amines 2a-c leads to the alkylamino-chlorodihexylamino-1,3,5-triazin…