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611.
Noriyuki Kogure 《Tetrahedron letters》2005,46(35):5857-5861
One new yohimbane and five new sarpagine-type indole alkaloids were isolated from the radix of Gelsemium sempervirens Ait. f., and their structures were determined by spectroscopic analysis, chemical conversion or total synthesis. It was found that 2-acyl sarpagine-type alkaloids possessing an Nb-methyl group take a keto-amino structure or a transannular form in solution depending on the solvent. 相似文献
612.
We report herein a concise and biomimetic synthesis of a precursor of barrenazine A, a cytotoxic alkaloid. The C2-symmetry of this molecule suggested the dimerization of an aminoketone, as the precursor of the central core pyrazine. This compound was prepared by assembly of aspartic acid and glycine. 相似文献
613.
Summary Velocity-difference induced focusing (V-DIF) of analytes by a dynamic pH junction represents a simple yet effective on-line
preconcentration method to improve concentration sensitivity in capillary electrophoresis (CE). Differences in buffer type,
pH and conductivity between sample and background electrolyte (BGE) segments of the capillary are properties used to optimize
purine focusing within a multi-section electrolyte system. This method permits the injection of large volumes of sample (up
to 450 nL or about 18% of capillary length), resulting in over a 50-fold improvement in sensitivity with baseline resolution.
The limit of detection (S/N=3) for xanthine is determined to less than 4.0×10−8 M under optimum conditions when using UV detection. Analysis of micromolar amounts of xanthine in pooled urine is also demonstrated
without sample pretreatment. A dual mechanism involving dynamic pH and isotachophoretic modes is proposed to enhance analyte
focusing performance when employing buffer pH junctions based on different types of electrolyte co-ions. 相似文献
614.
T. S. Tulyaganov 《Chemistry of Natural Compounds》2006,42(4):459-461
Three new alkaloids nitraridine (1), dihydronitraridine (2), and tetrahydronitraridine (3) were isolated from the aerial part of Nitraria komarovii. Their structures were established based on chemical transformations and spectral data. The compounds were synthesized. Spectral
properties of the komarovine subgroup of alkaloids were discussed.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 370–372, July–August, 2006. 相似文献
615.
本文从峨眉千里光(Sencic Fubcri Hensl)中分得二个吡咯里西啶类生物碱。经测定,一个为阔叶千里光碱(1),另一个为新阔叶千里光碱(2)。它们的~(1)H NMR研究尚未见报道。两者的~(13)C NMR研究已有报道,但1的许多~(13)C谱峰归属,不同的作者所得的结果不一致,而2的~(13)C谱峰归属与本文的二维NMR实验结果不一致。这二个化合物的NMR谱较为复杂,部分谱峰相互重选,其归属用一般方法不易确定。本文采用最近由我们提出的选择性远程~(13)CDEPT技术对这二个化合物的结构及其 相似文献
616.
A total synthesis of glypetelotine, the first sulphur-containing indole alkaloid from the leaf extracts of Glycosmis petelotii collected in the north of Vietnam, was described from indole through 6 steps. The structure of the glypetelotine was confirmed by IR, 1H NMR, 13C NMR and MS analysis. The spectral data of synthetic compound was identical with those of natural compound. 相似文献
617.
Balawant S. Joshi S. William Pelletier A. A. Ali Elizabeth M. Holt J. Phillip Bowen Tedman Ehlers 《Journal of chemical crystallography》2000,30(2):135-138
The crystal and molecular structure of augustamine (1), C17H19NO4 an amaryllidaceae alkaloid of the tazettine group has been determined by direct methods from single crystal x-ray diffractometer data and refined by full-matrix least squares. The alkaloid (1) crystallizes in the space group P212121, with cell parameters: a = 7.833(8) b = 11.08(2) å, c = 16.69(6) Å, Z = 4, Dc = 1.381 g/cm–3, R = 7.6% for 1115 observed reflections. The molecule, having a hexacyclic ring system, is very rigid with the ring B in a chair conformation. Molecular mechanics calculations have been made using MM3(2000) force field. 相似文献
618.
NaLI Qi Tai ZHENG Zhi Da MIN* Department of Natural Products Chemistry China Pharmaceutical University Nanjing Institute of Materia Medica Chinese Academy of Medical Sciences & Peking Union Medical College Xian Nong Tan street Beiji 《中国化学快报》2001,(10)
Pueraria peduncularis (Grah. ex Benth.) Benth. is a plant of Leguminosae which grows in the southwest of China. Different from other plants of Pueraria, it could not be used as a medicine due to its toxicity1. In order to use the Pueraria plants safer, we studied the constituents of P. peduncularis. Previous phytochemical studies of an n-BuOH extract afforded three triterpenoid saponins2-3. The continuing investigation on CHCl3 extract led to the isolation of a new indole alkaloid. … 相似文献
619.
采用高速逆流色谱(HSCCC)技术从铁棒锤根氯仿提取物中分离制备了一种高纯度咪唑类生物碱1H-imidazole-2-carboxylic acid,butyl ester (ICABE)。采用高效液相色谱(HPLC)测定目标化合物在两相溶剂中的分配系数,优化HSCCC分离ICABE的溶剂体系,确定了以正己烷-氯仿-乙醇-水(10:1:13:2,v/v/v/v)为HSCCC的两相溶剂系统,以上相为固定相,下相为流动相,流动相流速为1.8 mL/min,主机转速850 r/min,检测波长为230 nm条件下进行分离制备,在350 min内从100 mg粗样品中一步分离得到7.5 mg ICABE,经HPLC检测其纯度达98%以上(峰面积归一化法),结构由UV、1H-NMR和13C-NMR得以鉴定。该方法简便、快速,所得产物纯度高,适合于铁棒锤中ICABE的制备分离。 相似文献
620.
MA Jingwei KAN Hong MA Yinghui MEN Lihui PI Zifeng LIU Zhiqiang LIU Zhongying 《高等学校化学研究》2014,30(5):731-737
Ultra performance liquid chromatographic-electrospray ionization-mass spectrometry(UPLC-ESI-MS) was used to investigate the potential interaction between selected ingredients of Aconitum and fritillary. The efflux ratios of 14-benzoylmesaconine(BM), 14-benzoylaconine(BC), 14-benzoylhypaconine(BH), mesaconitine(MA), aco- nitine(AC) and hypaconitine(HA) was 11.16, 12.53, 11.69, 12.8, 11.03 and 6.15, respectively, and the secretion of them was inhibited by Veraparnil, which means they are the substrates of permeability-glycoprotein(P-gp). The transport of Aconitum alkaloids extract through a Caco-2 cell monolayer was determined in the absence and presence of fritillary extract. And the fritillary extract increased the absorption of Aconitum alkaloids. Peimine(PE) and peimi- nine(PEN) in fritillary increased the absorption of pure Aconitum alkaloids. The transport of digoxin was respectively enhanced by PE and PEN, which means they are the inhibitors of P-gp. PEN showed more effective inhibition than PE at the same concentration. The in vitro data suggest that the compounds such as fritillary present in alkaloids were able to inhibit the P-gp activity and lead modifying the transport of alkaloids. 相似文献