RESUMO
A new method for selective cleavage of 2-naphthylmethyl (NAP) ether utilizing 10-20 molar excess of HF/pyridine in toluene was revealed and strategically applied to a divergent approach towards generation of a high-mannose type oligosaccharide library.
Assuntos
Éter/química , Manose/química , Naftalenos/química , Oligossacarídeos/química , Ácido Fluorídrico/química , Oligossacarídeos/síntese química , Piridinas/química , Tolueno/químicaRESUMO
The activity and stability of a ß-glycosidase (Thermus thermophilus) and two α-galactosidases (Thermotoga maritima and Bacillus stearothermophilus) were studied in different hydrophilic ionic liquid (IL)/water ratios. For the ILs used, the glycosidases showed the best stability and activity in 1,3-dimethylimidazolium methyl sulfate [MMIM][MeSO(4)] and 1,2,3-trimethylimidazolium methyl sulfate [TMIM][MeSO(4)]. A close correlation was observed between the thermostability of the enzymes and their stability in IL media. At high IL concentration (80%), a time-dependent irreversible denaturing effect was observed on glycosidases while, at lower concentration (<30%), a reversible inactivation affecting mainly the k (cat) was obtained. The results demonstrate that highly thermostable glycosidases are more suitable for biocatalytic reactions in water-miscible ILs.
Assuntos
Glicosídeo Hidrolases/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biocatálise , Biotecnologia , Estabilidade Enzimática , Geobacillus stearothermophilus/enzimologia , Geobacillus stearothermophilus/genética , Glicosídeo Hidrolases/química , Glicosídeo Hidrolases/genética , Interações Hidrofóbicas e Hidrofílicas , Imidazóis , Líquidos Iônicos , Cinética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Temperatura , Thermotoga maritima/enzimologia , Thermotoga maritima/genética , Thermus thermophilus/enzimologia , Thermus thermophilus/genética , Água , alfa-Galactosidase/química , alfa-Galactosidase/genética , alfa-Galactosidase/metabolismoRESUMO
Synthesis of a tetrasaccharide related to the repeating unit of the O-antigen from Escherichia coli K-12 is reported in the form of its octyl glycoside. Syntheses of the 1,2-cis glycosidic linkages have been accomplished by using NIS in conjunction with H(2)SO(4)-silica, and it was found to be stereoselective and productive. The synthesized tetrasaccharide will be utilized as the substrate for galactofuranosyltransferase, WbbI.
Assuntos
Escherichia coli K12/imunologia , Antígenos O/química , Oligossacarídeos/síntese química , Sequência de CarboidratosRESUMO
H(2)SO(4)-silica-promoted removal of benzylidene, isopropylidene, trityl and tert-butyldimethylsilyl groups from sugar derivatives was accomplished by following an 'on-column' protocol in a virtually waste-free condition.
Assuntos
Alcenos/isolamento & purificação , Compostos de Benzilideno/isolamento & purificação , Compostos de Organossilício/isolamento & purificação , Dióxido de Silício/química , Sulfatos/química , Compostos de Tritil/isolamento & purificação , Alcenos/química , Compostos de Benzilideno/química , Hidrólise , Estrutura Molecular , Compostos de Organossilício/química , Compostos de Tritil/químicaRESUMO
Simple and convergent synthesis of a tetra- and a trisaccharide portions of an antitumor compound Julibroside J(28), isolated from Albizia julibrissin, that showed significant in vitro antitumor activity against HeLa, Bel-7402 and PC-3M-1E8 cancer cell lines is reported. The tetrasaccharide has been synthesized as its p-methoxyphenyl glycoside starting from commercially available D-glucose, L-rhamnose and L-arabinose. The trisaccharide part has been synthesized from commercially available N-acetyl D-glucosamine, D-fucose and D-xylose using simple protecting group manipulations. Sulfuric acid immobilized on silica has been used successfully as a Brönsted acid catalyst for the crucial glycosylation steps.
Assuntos
Albizzia/química , Antineoplásicos Fitogênicos/síntese química , Saponinas/química , Trissacarídeos/síntese química , Triterpenos/química , Antineoplásicos Fitogênicos/farmacologia , Sequência de Carboidratos , Células HeLa , Humanos , Dados de Sequência Molecular , Saponinas/farmacologia , Trissacarídeos/farmacologia , Triterpenos/farmacologiaRESUMO
Chemoselective hydrolysis of a variety of thioglycosides in the presence of a wide range of protecting groups has been achieved by using N-iodosuccinimide and H(2)SO(4) immobilized on silica in good to excellent yields.
