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131.
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133.
The two chiral spiro nucleosides 4 and 5 containing the barbituric acid moiety were efficiently synthesized from optically pure precursors, and their properties were studied. The carbocyclic nucleoside 5 is considerably more stable against ring opening than the deoxyribosyl derivative 4. Both compounds present enhanced hydrogen bonding capacity with diacetyladenosine. 相似文献
134.
Roulland E Monneret C Florent JC Bennejean C Renard P Léonce S 《The Journal of organic chemistry》2002,67(13):4399-4406
An enantioselective synthesis of new 12-amino alkylidenecyclopentenone prostaglandins is reported. The key step of the synthesis involved a [3.3] sigmatropic rearrangement of an asymmetric allylic cyanate to elaborate an asymmetric 5-amino-1,6-diene which was further transformed into cyclopentenone by successive ring-closing metathesis reaction catalyzed by the Grubbs reagent and one-pot oxidation. A palladium-catalyzed cross-coupling reaction on a 5-iodo-1,5-diene allowed the synthesis of prostanoids with variable Rw side chains. These new compounds exhibit high cytotoxic activities. 相似文献
135.
The iron/alumina catalysts prepared by the impregnation of Fe(CO)5 on the support have properties quite different from those of the conventional catalysts in the CO+H2 reaction. However, the preparation procedure or the activation of the solid has a decisive effect on the activity, selectivity and stability.
Fe(CO)5 , , CO+H2. , , .相似文献
136.
Bruno Delest Jean-Michel Robert Marie-Renée Nourrisson Muriel Duflos Pierre Renard 《Tetrahedron》2004,60(29):6079-6083
The synthesis of a novel tetracyclic structure, 8,9-dihydroimidazo[4,5-c]pyrrolo[3,2-g]quinolin-4(5H)-one, has been achieved by a convergent pathway. Coupling of the weakly nucleophilic hindered aromatic amine with 1-benzylimidazole-4-carboxylic acid, 7, afforded the corresponding amide 9 using a DCP/DMF complex; subsequent Heck-type arylation leading to desired tetracyclic molecule imidazo[4,5-c]-pyrrolo[3,2-g]quinolin-4(5H)-one. 相似文献
137.
Juice was prepared from cider apples of the cultivar "Kermerrien" under oxidative conditions. After isolation by solid-phase extraction, the phenolic fraction was subjected to high-performance liquid chromatography/electrospray ionisation mass spectrometry. SIM scans were performed at m/z values obtained in model solutions. The oxidation products, resulting from coupling between a molecule of caffeoylquinic acid and caffeoylquinic acid, catechin or dimeric flavan-3-ol, were detected. 相似文献
138.
The design and synthesis of novel self-immolative spacer systems aiming at the release of phenol-containing compounds are described. The newly designed traceless linkers proved to be conveniently stable under physiological conditions and operate through spontaneous decomposition of an hemithioaminal intermediate under neutral aqueous conditions. Their utility was then illustrated by the preparation of original fluorogenic substrates of penicillin amidase whose strong fluorescence is unveiled through enzyme-initiated domino reactions. 相似文献
139.
The field-free alignment of CO2 produced in response to the excitation of a molecule by a high-intensity femtosecond pump pulse is measured with a simple coronography-like technique. The technique is based on the defocusing of a time-delayed probe pulse produced by the spatial distribution of aligned molecules. In the intensity regime explored here, the technique is shown to give valuable information about dynamic alignment. With the help of simulations, the degree of alignment is extracted from the data. 相似文献
140.
F.M. Renard 《Physics letters. [Part B]》1975,60(1):55-57
We show how a symmetry property can lead simultaneously to broad states and to narrow states. We discuss then the origin of the symmetry breaking with respect to the properties of the narrow states recently discovered. 相似文献