Search results for "stereochemistry"

Calixarenes as Stoppers in Rotaxanes

1998

The synthesis of the amide-based rotaxane 7a bearing calix[4]arene blocking groups is described for the first time. While rotaxane formation fails if a calix[4]arene is functionalized at the upper rim with only an amino or methylamino group lacking any spacer, the prolonged amine 5a works successfully as stopper unit preventing dethreading of the dimeric wheel 1a by its size. Rotaxane formation of 8b was observed only by MALDI-TOF mass spectrometry of the reaction mixture of the amine 5b, the axle 6 and 1a. With the larger trimeric wheel 1b no stable rotaxane could be obtained. It either does not act as a concave template or its opening is too wide, even for the bulky calixarene stoppers.

ChemInform Abstract: Chemical and Chemoenzymatic Synthesis of Glycopeptide Selectin Ligands Containing Sialyl Lewis X Structures

2010

13C NMR Spectral Characterization of 4-Aryl-Substituted Bispyrazolo[3,4-b;4′,3′-e]pyridines

1996

A sesquiterpene ester from Lactuca serriola

1992

Abstract The aerial parts of Lactuca serriola yielded a new guaiane ester together with five known guaianolides.

Docking of Indolo- and Pyrrolo-pyrimidines to DNA New DNA-interactive Polycycles from 2-Amino-indoles/pyrroles and BMMA

2003

H2-Antihistaminika, 34. Mitt. 1,3,4-Oxadiazol-2,5-diamine mit H2-antagonistischer Aktivität

1987

Es wird uber die Synthese und H2-antagonistische Wirksamkeit von mono- und disubstituierten 1,3,4-Oxadiazol-2,5-diaminen mit Piperidinomethylphenoxypropylseitenkette sowie deren methylierte Derivate berichtet. H2-Antihistaminics, XXXIV: 1,3,4-Oxadiazole-2,5-diamines with H2-Antagonistic Activity Syntheses and H2-antagonistic activities of mono- and disubstituted 1,3,4-oxadiazole-2,5-diamines with a [(piperidinomethyl)phenoxy]propyl substituent and of their methyl derivatives are reported.

3-(1H-Indol-3-yl)-4-(3,4,5-trimethoxyphenyl)-2,5-dihydro-1H-pyrrole-2,5-dione

2005

The crystal structure of the title compound, C21H18N2O5, was determined in order to study the electrocyclic reactivity of 3,4-di­aryl-1H-pyrrole-2,5-dione derivatives. Intermolecular hydrogen bonds form sheets.

Novel bis(tetrahydropyrrolo[3,4-b]carbazoles) linked with aliphatic chains: synthesis and structural aspects

2001

Syntheses of novel bis(tetrahydropyrrolo[3,4-b]carbazoles) by a [4+2]cycloaddition reaction are described. By variation of dienophiles bis(tetrahydropyrrolo[3,4-b]carbazoles) of varying aliphatic spacer length could be obtained in high yields. These conformationally highly flexible molecules represent an interesting class of compounds, believed to have an affinity towards DNA, as potential DNA ligands.

Stereocontrolledα-Alkylation of Fully ProtectedL-Serine

2004

Diastereoselective alkylation of the (2S,4S) and (2R,4S) diastereomers of 3-tert-butyl 4-methyl 2-tert-butyl-1,3-oxazolidine-3,4-dicarboxylate (1a/b) is reported. Formation of both diastereomers of these oxazolidines was achieved by changing the order of protection steps, and their relative and absolute configurations were determined by NOESY spectroscopy. The use of the bulky ring substituent tBu together with Boc as the N-protecting group led to the exclusive formation of only one alkylated diastereomer. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Triazolopyridines. Part 24: New polynitrogenated potential helicating ligands

2004

The synthesis of novel 7-{[1,2,3]triazolo[1,5-a]pyridin-3-yl}-[1,2,3]triazolo[1,5-a]pyridines 7, 2-pyridyl-[1,2,3]triazolo[1,5-a]pyrid-7-ylmethanols 11, 3-(6-substituted-2-pyridyl)-[1,2,3]triazolo[1,5-a]pyridines 12, and 7,7′-disubstituted-3,3′-[1,2,3]triazolo[1,5-a]pyridine 20, interesting polynitrogenated ligands as potential helicating compounds or luminescent sensors, from [1,2,3]triazolo[1,5-a]pyridines is described.