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Pramchai Deelertpaiboon Suwatchai Jarussophon Patoomratana Tuchinda Chutima Kuhakarn Manat Pohmakotr 《Tetrahedron letters》2009,50(46):6233-6235
Treatment of glycals with trialkylaluminum in the presence of a catalytic amount of Yb(OTf)3 leads to the corresponding alkyl 2,3-unsaturated glycosides in good to excellent yields. Reactions of protected glycals are achieved under very mild conditions. 相似文献
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Gao JM Kamnaing P Kiyota T Watchueng J Kubo T Jarussophon S Konishi Y 《Journal of chromatography. A》2008,1208(1-2):47-53
Palmatine and its reduced form, dl-tetrahydropalmatine are a group of isoquinoline alkaloids that have been reported to display a variety of biological and pharmacological activities. Both drugs are hydrophilic and are difficult to be purified by conventional purification methods of natural products. A high-performance displacement chromatography (HPDC) method successfully purified palmatine and its semi-synthetic derivative dl-tetrahydropalmatine from crude extract of the African medicinal plant Enantia chlorantha. The crude extract from the root bark of E. chlorantha was fractionated on an analytical reversed-phase C(18) column by using 0.1% trifluoroacetic acid (TFA) or acetic acid/H2O as a carrier and cetylpyridinium trifluoroacetate (or acetate) (1.9mg/mL) in 0.1% TFA (or acetic acid)/H2O as a displacer. Palmatine was quantitatively purified at >98% purity in the fully developed displacement mode. dl-Tetrahydropalmatine was semi-synthesized by NaBH4 reduction from crude palmatine and directly purified by HPDC. Both palmatine and dl-tetrahydropalmatine were identified by high-resolution electrospray tandem mass spectrometry, (1)H NMR and (13)C NMR. This is the first report of one-step HPDC purification of natural and semi-synthetic products from a complex crude extract. 相似文献
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Manat Pohmakotr Kanhokthron Boonkitpattarakul Suwatchai Jarussophon Patoomratana Tuchinda 《Tetrahedron》2006,62(25):5973-5985
α,α-Difluoro-α-phenylsulfanyl-α-trimethylsilylmethane (PhSCF2SiMe3) has been demonstrated as an α,α-difluoro-α-phenylsulfanylmethyl carbanion equivalent. gem-Difluorophenylsulfanylmethylation of carbonyl compounds has been successfully achieved by using PhSCF2SiMe3 in the presence of TBAF in THF. The adducts have been converted to the corresponding gem-difluoroalkenes by a novel pyrolytic and/or FVP elimination of the β-hydroxy-α-phenylsufinyl derivatives under reduced pressure. 相似文献
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