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排序方式: 共有199条查询结果,搜索用时 15 毫秒
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[structure: see text] The structure of gelsemoxonine, isolated from Gelsemium elegans Benth., was revised to be a novel oxindole alkaloid having an azetidine unit. A new alkaloid, 14,15-dihydroxygelsenicine, which was presumed to be a biosynthetic precursor of gelsemoxonine, was also isolated. 相似文献
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Pattara Tiew Hiromitsu TakayamaMariko Kitajima Norio AimiUdom Kokpol Warinthorn Chavasiri 《Tetrahedron letters》2003,44(35):6759-6761
Three new compounds, mansoxetane; 4′-(3-hydroxy-1,2-oxetanyl)-2′,2-dihydroxy-4-(2-formyl-1-ethyl)-6′,6-dimethoxy biphenyl, and mansonones R and S, together with two previously reported coumarins, mansorins A and C, and four known mansonones, mansonones C, E, G and H, were obtained from the methanolic extract of the heartwood from Mansonia gagei Drumm. Their structures were established by spectroscopic methods. 相似文献
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Takehiko Yamato Fumika Kitajima Jeong Tae Gil 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3-4):257-262
The lower rim functionalized hexahomotrioxacalix[3]arene triamide 4 with cone-conformation was synthesized from triol 1 by a stepwise reaction. The different extractability for alkali metal ions, transition metal ions, and alkyl ammonium ions from water into dichloromethane is discussed. Due to the strong intramolecular hydrogen bonding between the neighboring NH and CO groups in triamide 4, its affinity to metal cations was weakened. Triamide 4 shows a single selectivity to n-BuNH 3 + . The anion complexation of triamide 4 was also studied by 1H NMR titration experiments. Triamide 4 binds halides through the intermolecular hydrogen bonding among the NH hydrogens of amide in a 1:1 fashion in CDCl3. The association constants calculated from these changes in chemical shifts of the amide protons are K a = 223 M?1 for Cl? and K a = 71.7 M?1 for Br?. Triamide 4 shows a preference for Cl? complexation than Br? complexation. 相似文献
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Yanagi T Kitajima A Anzai K Kodama K Mizoguchi J Fujiwara H Sakiyama H Kamoda O Kamei C 《Chemical & pharmaceutical bulletin》1999,47(11):1650-1654
Of 4-amino-5-chloro-2-methoxy-N-(1-ethyl-2-hydroxymethyl-4- pyrrolidinyl)benzamide, four optical isomers, (2S,4S)-1 (TKS159), (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27, were prepared from optically active 4-amino-1-ethyl-2-hydroxymethylpyrrolidine di-p-toluenesulfonate [(2S,4S)-14, (2S,4R)-17, (2R,4S)-20 and (2R,4R)-23, respectively]. The requisites, (2S,4S)-14, (2S,4R)-17, (2R,4S)-20 and (2R,4R)-23, were prepared from a commercially available trans-4-hydroxy-L-proline. The absolute configurations of (2S,4S)-1 (TKS159), (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27 were spectroscopically determined. Of the benzamide derivatives, four optical isomers, (2S,4S)-1, (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27, showed a relatively potent affinity for 5-hydroxytryptamine 4 (5-HT4) receptors in a radioligand binding assay ([3H]GR113808). The activities of 25-27 were less effective than that of 1 for the gastric emptying of a phenol red semisolid meal in rats. All this suggests that the most potent of the isomers was 4-amino-5-chloro-2-methoxy-N-[(2S,4S)-1-ethyl-2- hydroxymethyl-4-pyrrolidinyl]benzamide (1). 相似文献
8.
Takehiko Yamato Fumika Kitajima Jeong Tae Gil 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3):257-262
The lower rim functionalized hexahomotrioxacalix[3]arene triamide 4 with cone-conformation was synthesized from triol 1 by a stepwise reaction. The different extractability for alkali metal ions, transition metal ions, and alkyl ammonium ions from water into dichloromethane is discussed. Due to the strong intramolecular hydrogen bonding between the neighboring NH and CO groups in triamide 4, its affinity to metal cations was weakened. Triamide 4 shows a single selectivity to n-BuNH3+. The anion complexation of triamide 4 was also studied by 1H NMR titration experiments. Triamide 4 binds halides through the intermolecular hydrogen bonding among the NH hydrogens of amide in a 1:1 fashion in CDCl3. The association constants calculated from these changes in chemical shifts of the amide protons are Ka = 223 M−1 for Cl− and Ka = 71.7 M−1 for Br−. Triamide 4 shows a preference for Cl− complexation than Br− complexation. 相似文献
9.
Mariko Kitajima 《Tetrahedron letters》2006,47(19):3199-3202
A new pyrrolidinoindoline-type alkaloid, CPC-1, and a new tryptamine-derived dimeric alkaloid, CPC-2, were isolated from the seeds and rinds of Chimonanthus praecox f. concolor. The structure including the absolute configuration of CPC-1 was determined by chiral total synthesis. CPC-2 has a unique hexahydropyrroloquinoline skeleton. 相似文献
10.
As the glycosyl constituents of Ficus pumila L. fruits (Moraceae), three new sesquiterpenoid glucosides, pumilasides A, B and C were isolated together with benzyl beta-D-glucopyranoside, (E)-2-methyl-2-butenyl beta-D-glucopyranoside and rutin. Their structures were characterized as (1S,4S,5R,6R,7S,10S)-1,4,6-trihydroxyeudesmane 6-O-beta-D-glucopyranoside, (1S,4S,5S,6R,7R,10S)-1,4-dihydroxymaaliane 1-O-beta-D-glucopyranoside and 10 alpha, 11-dihydroxycadin-4-ene 11-O-beta-D-glucopyranoside by spectral and chemical methods. 相似文献