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1.
Dirk Schwäbisch 《Journal of fluorine chemistry》2004,125(1):119-124
Starting with 1,2,4,6-tetra-O-acetyl-3-O-dodecyl-β-d-glucose (1), mixed alkyl-perfluoroalkyl substituted sugar derivatives with an anomeric perfluoroalkylthio group and an O-alkyl group in the 3 position were synthesized via 2,4,6-tri-O-acetyl-3-O-dodecyl-1-thio-β-d-glucose (4). The latter was S-perfluorohexylated with 1-iodoperfluorohexane in a dithionite initiated reaction yielding perfluorohexyl 2,4,6-tri-O-acetyl-3-O-dodecyl-1-thio-β-d-glucopyranoside (5). Experiments with the aim compound 5 completely to deacetylate ended in surprising results. Thus, methanolic methanolate solution produced the orthoester 7 as the result of α-fluoride replacement by methoxy groups as well as the methyl glucoside 8 as the result of a transglycosylation reaction. Alumina supported cesium fluoride cleaved regioselectively the two acetyl groups in the 4- and 6-position yielding perfluorohexyl 2-O-acetyl-3-O-dodecyl-1-thio-β-d-glucopyranoside (10). A complete deacetylation of 5 to amphiphile 11 succeeded only with methanolic tert-butanolate. However, the products 8 and 10 were likewise formed. 相似文献
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Atsuko Nakamura 《Tetrahedron letters》2005,46(37):6373-6376
Xestobergsterol A, a potent inhibitor of histamine release, has been synthesized from dehydroepiandrosterone in a route that used introduction of a novel 15-oxygen functionality, side-chain construction via the orthoester Claisen rearrangement and TBAF-promoted epimerization-aldol condensation. 相似文献
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Keisuke Kato Hideaki Nouchi Satoshi Takaishi Hikaru Tanaka Tomoyuki Mochida Koki Shigenobu 《Tetrahedron》2006,62(11):2545-2554
The oxidative cyclization-carbonylation of propargylic esters mediated by Pd(II) afforded cyclic orthoesters, which were hydrolyzed into γ-acetoxy-β-ketoesters. Based on the NMR experiments, it was presumed that the cyclization reaction was initiated by a nucleophilic attack of carbonyl oxygen to the alkyne carbon coordinated to palladium(II). When the γ-acetoxy-β-ketoesters were treated with a basic condition, Knoevenagel-Claisen type condensation took place, and spiro furanone derivatives were obtained in good yields. We applied these reactions to steroid derivatives, and steroid derivatives having a spiro furanone fragment were synthesized. Among them, the spiro furanone 4j had vasorelaxant and bradycardiac activities. Compounds 2i-4k had inhibitory effect on CYP3A. 相似文献
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Kana M. Sureshan 《Tetrahedron》2009,65(13):2703-5526
A metal mediated unusual 1-3 acyl migration from C4-O to C2-OH of myo-inositol 1,3,5-orthoformate was observed during the alkylation of racemic 4-O-benzoyl-myo-inositol 1,3,5-orthoformate. This has been exploited for the selective esterification of either the C4(6)-OH or the C2-OH of myo-inositol by varying the amount of the base used. While the use of 1 equiv of the base (sodium hydride or potassium tert-butoxide) for the acylation of myo-inositol orthoesters gives the corresponding C4-ester exclusively, the use of two or more equivalents of base for the same reaction gives the C2-ester exclusively. The relatively higher stability of the alkoxide of racemic 2-O-acyl-myo-inositol 1,3,5-orthoester as compared to the alkoxide of 4-O-acyl-myo-inositol 1,3,5-orthoester is suggested to be responsible for the observed isomerization. 相似文献
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A one-pot synthesis of some unsymmetrical 2,5-disubstituted-1,3,4-oxadiazoles via cyclocondensation of benzoylhydrazines with orthoesters under solvent-free and microwave conditions are described here. The reaction is efficiently catalyzed by silica- supported sulfuric acid as it provided the title compounds in high yields and relatively short times. The catalyst is reusable and can be applied several times without considerable decrease in the yields and rates of the reactions. 相似文献
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Ahmad Shaabani Abbas Rahmati Elham Farhangi Ali Hossein Rezayan 《Monatshefte für Chemie / Chemical Monthly》2007,138(6):615-618
Summary. A novel class of 3,4-dihydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones was synthesized in very short reaction times with good yields in the presence of 3-butyl-1-methyl imidazolium bromide
as a room temperature ionic liquid at 120°C. The ionic liquid can be recycled for subsequent reactions without any loss of
efficiency. 相似文献
10.
Armin Presser Olaf Kunert Irmgard Pötschger 《Monatshefte für Chemie / Chemical Monthly》2006,137(3):365-374
Summary. Several improved approaches for the preparation of tetra-O-benzyl-α-D-glucopyranosyl bromide and tetra-O-pivaloyl-α-D-glucopyranosyl bromide are discussed. The importance of these compounds, which are useful glycosyl donors, was demonstrated
by successful preparation of cholesteryl glucopyranosides in an almost neutral medium without the formation of orthoesters.
In addition, accurate 1H and 13C NMR resonance assignments of the synthesized cholesteryl glycosides were performed by 2D NMR spectroscopy. 相似文献