共查询到20条相似文献,搜索用时 125 毫秒
1.
2.
自菊科蒿属植物万年蒿(Artemisia Sacrorum Ledeb)地上部分首次分得三个贝壳杉烷型(Kauranetape)二萜类化合物,经理化常数测定及光谱分析(IR,’H-NMR,~(13)C-NMR,MS,二维核磁共振光谱)鉴定其结构分别为:3α,16α,17-三羟基贝壳杉烷[I],3α,16α-二羟基贝壳杉烷-17-0-β-D-葡萄糖甙[Ⅱ]和16α-羟基贝壳杉-3-酮-17-0-β-D-葡萄糖甙[Ⅲ]。其中[Ⅰ]为一新天然产物,[Ⅱ]为一未见报道的新化合物。通过对该三个化合物的~(13)C-NMR光谱分析,讨论了不同位置取代基对其~(13)C-NMR光谱化学位移的影响。 相似文献
3.
4.
~(13)C-NMR是分析有机化合物碳链结构的有效手段,但对于某些化合物特别是聚合物,很难找到已知结构的标准谱图来对照确定其结构。近年来发表的饱和链烃~(13)C-NMR 化学位移计算公式因计算过程较繁,笔算很费时间。本文介绍的用 PC-1500袖珍计算机计算的方法,不仅能算出~(13)C-NMR 化学位移并能模拟~(13)C-NMR 谱图,快速、简便、直观,几分钟内即可 相似文献
5.
6.
三萜和甾体是由六个异戊二烯单元组成的一大类天然产物,具有复杂多样的化学结构和广泛的生物活性.真菌是三萜和甾体化合物发现的重要源泉,但与植物相比,目前从真菌中发现的三萜骨架类型仍然很少,仍有较大的研究空间.基因组挖掘已成为后基因组时代发现新颖天然产物的重要手段,其主要通过与相似功能基因的比较来发现新功能基因.随着高通量测序技术和生物信息技术的飞速发展,一些具有重要生物活性的真菌三萜或甾体的生物合成途径逐渐被阐明,这为利用基因组挖据手段从真菌中发现新颖三萜或甾体化合物奠定了基础.重点介绍近年来在真菌三萜或甾体生物合成方面的研究进展情况. 相似文献
7.
计算机辅助有机化合物结构解析工作可粗分为数据库检索和人工智能解析两大类。本文通过子结构(本文中的子结构是以碳原子为中心的β层子结构,以下同)与~(13)C-NMR谱相关性研究,并建立~(13)C-NMR谱自动解析系统。首先,采用统计方法,由已知波谱数据寻求共振碳的β层环境结构与共振碳化学位移的对应范围,产生以碳为中心原子的β层子结构-~(13)C-NMR谱相关表。在解析未知化合物结构时,由未 相似文献
8.
9.
10.
本文系统介绍了结构解析专家系统ESESOC.I.的研制过程。该系统能够综合利用IR,~1H-NMR,~(13)C-NMR对含有C,H,O的有机化合物结构进行自动解析。 相似文献
11.
通过几个应用例子 ,说明了作者建立的Sadtler标准碳谱检索系统是有机物定性分析和结构指定的必备工具之一 相似文献
12.
Ljubrinka Lorenc Lidija Bondarenko Vlada Pavlovi Hermann Fuhrer Grety Rihs Jaroslav Kalvoda Mihailo Lj. Mihailovi 《Helvetica chimica acta》1989,72(3):608-623
Thermolysis of steroidal 5α, 8α- peroxides of type 3a-d generates as major products the corresponding diseco compounds containing a 14-membered ring instead of the standard A-B-C-ring skeleton. Depending on the reaction conditions, either the primary products of type 9 or the α, β-unsaturated ketones of type 4 , formed by subsequent elimination of AcOH, are isolated. The latter, configurationally uniform compounds undergo epoxidation of the C(9)=C(10) bond followed by a Baeyer-Villiger oxidation to give, as final products, the 15-membered cyclic epoxyenol lactones of type 20 and 21 . The structures of the various products were determined by 1H- and 13C-NMR spectroscopy. The conformations of the 14- and 15-membered rings were established by X-ray structure analyses of 7 and 21a . A reaction mechanism for the above transformations is discussed. 相似文献
13.
A new steroidal saponin was isolated from the leaves of Agave attenuata. Its structure was established as (3beta,beta,25S)-spirostan-3-yl O-beta-D-glucopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 2)-O-[beta-D-glucopyranosyl-(1 --> 3)]-beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranoside. The structural identification was performed using detailed analyses of 1H- and 13C-NMR spectra including 2D NMR spectroscopic techniques (COSY, HETCOR, and COLOC) and chemical conversions. The hemolytic activity of the steroidal saponin was evaluated using an in vitro assay. 相似文献
14.
A new steroidal saponin was isolated from the leaves of Agave shrevei. Its structure was established as 3-[O-beta-D-glucopyranosyl-(1-->2)-O-[O-beta-D-glucopyranosyl-(1-->4)-O-[O-beta-D-glucopyranosyl-(1-->6)]-O-beta-D-glucopyranosyl-(1-->4)-beta-D-galactopyranosyl)-oxy]-(3beta,5alpha,25R)-spirostane. The structural identification was performed using detailed analyses of 1H- and 13C-NMR spectra including 2D NMR spectroscopic techniques (COSY, HETCOR, HMBC, and HMQC) and chemical conversions. The haemolytic activity of the steroidal saponin was evaluated using an in vitro assay. 相似文献
15.
Zheng Chong-zhi Qian Cheng Wang Yuan Cheng Wei-ming Yuan Shen-gang Hui Yong-zheng 《Analytica chimica acta》1989
The configuration of a computerized information system for organic chemistry is outlined. Data banks for infrared, 13C-NMR, mass and x-ray diffraction spectra are accessed individually or from a central structure-handling and search system. Other facilities include a Chinese chemical documentation system, accessible in English or Chinese, and data analysis by multivariate techniques. 相似文献
16.
17.
The expert system CARBON is built around a knowledge base consisting of spectra/structure correlations, tables of data, mathematical formulae and graph-theory procedures and on a data base of 2500 assigned 13C-NMR spectra. The built-in knowledge enables the user to obtain suggestions for solutions to problems of different types arising in 13C-NMR spectroscopy. Use of the system is facilitated by appropriate command files, large on-line help files, and user-friendly dialogue. The system can be used with spectrometries other than 13C-NMR and in other fields concerned with correlations between chemical structures and properties. 相似文献
18.
ComputerHandlingofChemicalandBiologicalDataofTraditionalChineseMedicinesCHEChun-taoa**,PaulR.CarlieraandOpheliaC.W.Leeb(aDepa... 相似文献
19.
Accurate, practical prediction of 13C NMR chemical shifts has been achieved with a new system, CAST/CNMR, taking account of stereochemistry. The CAST/CNMR system has solved the critical problem of the accurate distinction of differences and similarities in stereochemical structures around a specific carbon, which has not yet been achieved by any other database-oriented system for prediction of 13C NMR chemical shifts. CAST/CNMR uses a three-dimensional structural database together with a 13C NMR spectral database. Absolute/relative configurational and conformational structural information are described by the CAST (CAnonical-representation of STereochemistry) coding method. This paper provides an overview of the CAST/CNMR system, and describes its application to two natural products as examples. 相似文献
20.
Diarylheptanoids, natural products with a 1,7-diphenylheptane structural skeleton, are mainly distributed in the roots, rhizomes and bark of Alpinia, Zingiber, Curcuma and Alnus species. They have become of interest in natural product research over the past twenty years because of their remarkable anti-cancer, anti-emetic, estrogenic, anti-microbial and anti-oxidant activity. This paper compiles all 307 naturally occurring diarylheptanoids from 46 plants as reported in 137 references with their distributions, physiological activities and 13C-NMR spectral data. 相似文献