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白花刺参中两个新三萜皂苷 总被引:2,自引:0,他引:2
从著名藏药白花剌参(Morina nepalensis var.alba Hand-Mazz)全草的水溶 性部分中分离得到两个新的乌苏烷型三萜皂苷,命名为剌参苷A(1)和剌参苷B(2). 应用2DNMR新技术,包括^1H-^1H COSY,HSQC,HMBC,2D HMQC-TOCSY,ROESY,以 及选择性激发实验1D SELTOCSY和1D SELNOESY,并结合化学方法,确定它们的结构 分别为3-O-a-L-阿拉伯吡喃糖基-(1→3)-α-L-阿拉伯吡喃糖基坡摸醇酸28-O-β -D-葡萄吡喃基-(1→6) -β-D-葡萄吡喃糖苷(1)和3-O-a-L-阿拉伯吡喃糖基-( 1→3)-β-D-木糖吡喃基坡摸醇酸28-O-β-D-葡萄吡喃基-(1→6) -β-D-葡萄吡喃 糖苷(2),并对其氢和碳的化学位移进行了全归属。 相似文献
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珠子参化学成分分析 总被引:6,自引:0,他引:6
从珠子参根茎中分离得到7个化合物. 利用核磁共振、 质谱和红外等手段, 并结合其理化性质, 鉴定了其结构, 它们分别是24(R)-珠子参苷R1, 6-O-[β-D-吡喃葡萄糖基(1→2)-β-D-吡喃葡萄糖基]-20-O-[β-D-吡喃葡萄糖基(1→4)-β-D-吡喃葡萄糖基]-20(S)-原人参三醇、 6″-乙酰基-人参皂苷Rd、 人参皂苷Rf、 竹节参皂苷Ⅳa、 人参皂苷Rd和竹节参皂苷Ⅴ. 其中, 24(R)-珠子参苷R1和6-O-[β-D-吡喃葡萄糖基(1→2)-β-D-吡喃葡萄糖基]-20-O-[β-D-吡喃葡萄糖基(1→4)-β-D-吡喃葡萄糖基]-20(S)-原人参三醇为2个新化合物, 6″-乙酰基-人参皂苷Rd 和人参皂苷Rf为首次从珠子参根茎中得到. 相似文献
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从萝摩科植物海枫藤[Marsdenia officinalis Tsiang et P.T.Li.]的藤茎中分离得到四个C21甾体去氧糖苷(1)~(4). 通过化学降解和波谱技术, 确定它们的化学结构依次为: 12-O-桂皮酰基-20-O-乙酰基(20S)-孕甾烷-6-烯-3β,5α,8β,12β,14β, 17β,20-庚醇 3-O-甲基-6-去氧-β-D-阿洛吡喃糖基-(1→4)-β-D-夹竹桃吡喃糖基-(1→4)-β-D-磁麻吡喃糖苷(1), 12-O-桂皮酰基-20-O-乙酰基(20S)-孕甾烷-6-烯-3β,5α,8β,12β,14β,17β,20-庚醇3-O-β-D-葡萄吡喃糖基-(1→4)-3-O-甲基-6-去氧-β-D-阿洛吡喃糖基-(1→4)-β-D-磁麻吡喃糖基-(1→4)-β-D-磁麻吡喃糖苷(2), 12-O-桂皮酰基-20-O-乙酰基(20S)-孕甾烷-6- 烯-3β,5α,8β,12β,14β,17β,20-庚醇3-O-β-D-黄夹吡喃糖基-(1→4)-β-D-磁麻吡喃糖基-(1→4)-β-D-磁麻吡喃糖苷(3), 12-O-烟酰基-肉珊瑚苷元3-O-β-D-葡萄吡喃糖基-(1→4)-3-O-甲基-6-去氧-β-D-阿洛吡喃糖基-(1→4)-β-D-夹竹桃吡喃糖基- (1→4)-β-D-磁麻吡喃糖基-(1→4)-β-D-磁麻吡喃糖苷(4). 其中1和2为新化合物, 分别命名为haifengtenoside A, haifengtenoside B, 3和4分别为已知化合物mucronatoside H 和 hainaneosides A, 系首次从该植物中分离得到. 相似文献
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蒺藜草中一个新的六糖甾体皂甙结构的NMR研究 总被引:2,自引:0,他引:2
从蒺藜草中分离得到一个新的六糖甾体皂甙,利用NMR方法,特别是2D NMR技术,确定了它的化学结构3-O-{β-D-吡喃木糖基-(1→3)-[β-D吡喃木基-(1→2)]β-D-吡喃葡萄糖甙-(1→4)-[α-L吡喃鼠李糖基-(1→2)]-β-D吡喃半乳糖基}-22-甲氧基-26-O{β-D-吡喃和葡萄糖基}-蒺藜皂甙元。 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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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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《Tetrahedron》2014,70(21):3377-3384
The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative. 相似文献
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Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner. 相似文献
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Hao Xu Liyang Pan Xiaomin Fang Baoying Liu Wenkai Zhang Minghua Lu Yuanqing Xu Tao Ding Haibo Chang 《Tetrahedron letters》2017,58(24):2360-2365
A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis. 相似文献
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A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs). 相似文献
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Andrey A. BerezinPanayiotis A. Koutentis 《Tetrahedron》2011,67(22):4069-4078
Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO4 oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised. 相似文献