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本文报道从猪去氧胆酸出发,通过呋喃负离子与22-甾醛的反应以构成油菜甾醇内酯及其一类物侧链,获得了一个合成油菜甾醇内酯及其一类物的关键中间体。 相似文献
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头孢克肟侧链的合成研究 总被引:4,自引:0,他引:4
介绍了头孢克肟的抗菌活性。综述了头孢克肟侧链的合成方法,提出了从氯乙酰乙酸乙酯为原料经肟化、缩合2步反应合成头孢克肟侧链是一条适合于工业化生产的工艺路线。参考文献20篇。 相似文献
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本文报道从猪去氧胆酸立体选择性地构成26,27-双失碳油菜甾醇内酯的侧链。关键步骤是20-碳醛化合物3与2-锂-2-异丙基1,3-二噻烷4的高立体选择反应,同时报道了26,27-双失碳香蒲甾醇11的合成,它是新化合物,它的生物活性正在测定之中。 相似文献
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本文报道以猪去氧胆酸为原料,立体选择性地合成(SS2,23S)-香蒲甾醇,合成的关键步骤是用Li2Cu3(CH3)5立体专一地转化烯丙醇苯胺基甲酸酯10和13成为11和用OsO4-NMO在化合物16的不饱和侧链上立体选择性羟基化。 相似文献
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本文报道以猪去氧胆酸为原料,立体选择性地合成(22S,23S)-香蒲甾醇。合成的关键步骤是用Li_2Cu_3(CH_3)_5立体专一地转化烯丙醇苯胺基甲酸酯10和13成为11和用OsO_4-NMO在化合物16的不饱和侧链上立体选择性羟基化。 相似文献
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我国资源丰富的猪去氧胆酸(1)可以用作合成油菜甾醇内酯(2)、α-蜕皮甾酮(3)和维生素D代谢物4的原料.合成的关键是猪去氧胆酸侧链的改造.本文报道从猪去氧胆酸氧化脱羧所得到的△~(22)-甾烯(5)分别转变成合成上述化合物的中间体6,7和8,并利用从5经臭氧化制得的9合成了一个油菜甾醇内酯和α-蜕皮甾酮的共同中间体10. 相似文献
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油菜甾醇内酯(brassinolide)(1)是一种高效植物生长激素,一些实验室曾成功地进行了合成(图1)。这些合成路线不少是以20-S-22-甾醛为关键中间体,再分步接上侧链的,而C_(20)-S-22-甾醛大都由豆甾醇为原料制得。考虑到豆甾醇来源困难,我们采用国内资源丰富、价格低廉的薯蓣皂甙元为起始原料,立体选择性地合成了C_(20)-S-22-甾醛化合物7(见图2),对1及其 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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