Oxadiazole derivatives R 0290Microwave-Induced One-Pot Synthesis of 4-[3-(Aryl)-1,2,4-oxadiazol-5-yl]-butan-2-ones under Solvent-Free Conditions. -A practical and rapid procedure is developed for the microwave-promoted synthesis of 1,2,4-oxadiazoles from methyl levulinate and arylamidoximes. The yields are comparable to the conventional process using levulinic acid. -(DE FREITAS, J. J. R.; DE FREITAS, J. C. R.; DA SILVA, L. P.; DE FREITAS FILHO*, J. R.; KIMURA, G. Y. V.; SRIVASTAVA*, R. M.; Tetrahedron Lett. 48 (2007) 35, 6195-6198; Dep. Quim. Fundam., Univ. Fed. Pernambuco, 50670 Recife, Brazil; Eng.) -Mais 50-147
A reação de triO -acetil-D-glucal (1) com cicloexanol (2) usando o método de Ferrier forneceu o glicosídeo cicloexílico insaturado 3, que por sua vez produziu o composto 12 através da seqüência envolvendo hidrólise, tritilação seletiva no oxigênio do C-6, oxidação alílica e cicloadição dipolar 1,3 com diazometano. O produto 17 foi obtido em quatro etapas a partir de 6. Cálculos semiempíricos de orbitais moleculares (AM1) para o composto 12 forneceram a conformação estável e também apoiaram a existência do efeito anomérico. Foi feito um esforço para abrir o anel pirazolínico dos compostos 12 e 17, porém não tivemos sucesso. A carga negativa parcial no C-3 foi responsável pela falta de reatividade deste carbono frente a redução da ligação C=N. Reaction of triO -acetyl-D-glucal (1) with cyclohexanol (2) using Ferrier's method provided the unsaturated cyclohexyl glucoside 3, which furnished the title compound 12 in a sequence involving hydrolysis, selective tritylation of oxygen at C-6, allylic oxidation with MnO 2 and 1,3-dipolar cycloaddition with diazomethane. Starting from 6, product 17 was obtained in four steps. Semiempirical molecular orbital calculations (AM1) were carried out for compound 12 which gave an idea about its stable conformation, and also supported the existence of the anomeric effect. Attempts to open the pyrazoline ring in 12 and 17 failed. Partial negative charge at C-3 was responsible for the lack of reactivity of 12 towards reduction of C=N bond.
Synthesis and Hypolipidemic Activity of N-Phthalimidomethyl Tetra-O-acyl-α-D-mannopyranosides. -Compounds (III), (VI), (VII), (IX), and (XI) are tested for their hypolipidemic activities. (IX) shows the highest activity. -(SRIVASTAVA, RAJENDRA M.; OLIVEIRA, FERNANDO J. S.; DA SILVA, LADJANE P.; DE FREITAS FILHO, JOAO R.; OLIVEIRA, SHALOM P.; LIMA, VERA L. M.; Carbohydr. Res. 332 (2001) 3, 335-340; Dep. Quim. Fundam., Univ. Fed. Pernambuco, 50670 Recife, Brazil; EN)
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