Search results for "stereochemistry"
showing 10 items of 4831 documents
Hierarchical halogen bonding induces polymorphism
2009
Co-crystals of 1-iodo-3,5-dinitrobenzene and 1,4-diazabicyclo[2.2.2]octane manifest either two strong or one strong and one weak intermolecular 2 : 1 halogen bond (XB) motifs in polymorphic structures I and II, respectively, whereas weaker XB-donor 4,4-bipyridine just forms 1 : 1 structure III with one strong halogen bond.
Topical Anti-Inflammatory Lignans from Haplophyllum hispanicum Haplophyllum hispanicum
1996
The present paper reports the results of the methanol extract of Haplophyllum hispanicum Spach on single or repeated local 12-O-tetradecanoylphorbol acetate (TPA) administration and in the oxazolone-induced contact-delayed hypersensitivity mouse ear edemas. Two topical anti-inflammatory aryl naphthalide lignans were isolated from the active fractions of the methanol extract. They were identified by spectroscopic methods, including 13C NMR and heteronuclear multiple bond correlation (HMBC), as diphyllin acetyl apioside and tuberculatin. The former was the most active on acute TPA edema with a ID50 of 0.27 μmol/ear
Unequivocal determination of isomeric products of reaction between 3-methyl-1-phenyl-2-pyrazoline-4,5-dione and aromatic 1,2-diamines
1999
Abstract Regioselectivity of condensation of 3-methyl-1-phenyl-2-pyrazoline-4,5-dione with aromatic 1,2-diamines is dependent on substituent present. Isomeric 3-methyl-1-phenyl-1H-pyrazolo-[3,4-b]-quinoxaline products are distinguished by comparison of their 2D z-gradient selected 1H, 15N HMBC (Heteronuclear Multiple Bond Correlation) spectra. Multiplicity of H5 signal, which is recognizable by the cross-peak for CH3(3)-N4 and H5-N4 interactions, indicates substitution in position 6 or 7. The applied method is expected to be useful for structure determinations in other positional isomers.
H2-Antihistaminika, 25. Mitt. Synthese und H2-antagonistische Wirkung monosubstituierter 1,2,4-Oxadiazol-3,5-diamine
1985
Es wurden die N3- bzw. N5-substituierten 1,2,4-Oxadiazol-3,5-diamine 4a-e und 5a-e dargestellt und auf Histamin-H2-antagonistische Aktivitat untersucht. H2-Antihistaminics, XXV: Synthesis and H2-Antagonistic Activity of Monosubstituted 1,2,4-Oxadiazole-3,5-diamines The N3-or N5-substituted 1,2,4-Oxadiazole-3,5-diamines 4a-e and 5a-e were prepared and tested for histamine H2-antagonistic activity.
3-(4-Fluorophenyl)-4-(4-pyridyl)quinolin-2(1H)-one
2006
The title compound, C20H13FN2O, has the quinolin-2(1H)-one unit in the lactam form. The molecules form rows along the b axis via N—H⋯N hydrogen bonds
ChemInform Abstract: Cyclocondensation of 6-Acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with Hydroxylamine and Hydrazine.
2010
The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4a) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4b), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane (5). The structure determination of the compounds obtained is based on 1H and 13C nmr spectra including NOE measurements.
Dehydrotriphenylene zum Aufbau gewinkelter molekularer Bandstrukturen
1998
Dehydrotriphenylenes for the Generation of Bent Molecular Ribbons The synthetic sequences 1 11 and 17 23a lead to highly reactive mono- and bisdienophiles whose cycloaddition processes with in situ generated isobenzofuran 13 were studied: 11 + 13 15 and 23a + 2×13 24a.
ChemInform Abstract: Stereoselective Synthesis of Quinolizidine Alkaloids: (-)-Lasubin II.
2008
Initially, lasubin II was synthesized diastereoselectively in racemic form [3]. Asymmetric syntheses of lasubin II were achieved based on stereoselective transformations of enantiomerically pure substrates [4] or, for example, via a diastereoselective aza-Diels-Alder reaction using a resolved chiral arylaldehyde tricarbonylchromium complex [5]. Recently, an enantioselectively catalyzed aza-Diels-Alder reaction [6] and a [2+2+2] cycloaddition reaction [7] were successfully used for the synthesis of enantiomerically pure lasubin II.
Stereoselective Synthesis of Quinolizidine Alkaloids: (–)-Lasubin II
2008
Initially, lasubin II was synthesized diastereoselectively in racemic form [3]. Asymmetric syntheses of lasubin II were achieved based on stereoselective transformations of enantiomerically pure substrates [4] or, for example, via a diastereoselective aza-Diels-Alder reaction using a resolved chiral arylaldehyde tricarbonylchromium complex [5]. Recently, an enantioselectively catalyzed aza-Diels-Alder reaction [6] and a [2+2+2] cycloaddition reaction [7] were successfully used for the synthesis of enantiomerically pure lasubin II.
H2-Antihistaminica, 1. Mitt.: 2-Substituierte 4-[[2-(N′-Methyl-thioureido)-äthylmercapto]-methyl]-imidazole
1976
Es wird die Synthese der 2-substituierten 4-[[2-(N′-Methylthioureido)-athylmercapto]-methyl]-imidazole 5a–f als potentielle H2-Antihistaminica beschrieben. Ausgehend von den Imidazol-4-carbinolen 3a–f lassen sich die 2-substituierten 4-[(2-Amino-athylmercapto)-methyl]-imidazole 4a–f durch saurekatalysierte Reaktion mit Cysteamin darstellen und mit Methylisothiocyanat in die entsprechenden Thioharnstoffderivate 5 uberfuhren. 2-Substituted 4-[[2-(N′-Methyl-thioureido)-ethylmercapto]-methyl]-imidazoles The synthesis of 2-substituted 4-[[2-(Ns′-methyl-thioureido)-ethylmercapto]-methyl]-imidazoles 5a–f, as potential H2-antihistaminics, is described. The acid catalyzed reaction of the imidazole-4…