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排序方式: 共有310条查询结果,搜索用时 15 毫秒
1.
合成丙交酯中微量水分分析 总被引:3,自引:0,他引:3
合成丙交酯中微量水分分析徐溢,柳胜春(重庆大学化工学院分析教研室630044)关键词丙交酯,微量水,定量分析丙交酯是人工合成骨材料聚乳酸的合成中间体,其性能决定着合成产品的品质,要获得高质量的合成材料,对中间体的分析和监测十分重要。一般要求丙交酯中间... 相似文献
2.
Sesquiterpene Lactone Glycosides from Carpesium macrocephalum 总被引:1,自引:0,他引:1
Two new sesquiterpene lactone glycosides were isolated from the seeds of Carpesium meacrocephalum. Their structures were elucidated as 2α-O-β-D-glucopyranosy-5α,11αH-eudesma-4(15)-en-12,8β-olide and 2α-O-β-D-glucopyranosy-5αH-eudesma-4(15),11(13)-dien-12,8β-olide by spectral methods (HRMS,1D and 2D NMR). 相似文献
3.
An efficient and stereodefined process is described for the first preparation of a new prenyl-benzoylfuranone type sesquiterpenoid, (±)-3-(2,4-dihydroxybenzoyl)-4,5-dimethyl-5-(4,8-dimethyl-3(E),7(E)-nonadien-1-yl)tetrahydro-2-furanone. The synthetic strategy is based on nucleophilic addition of organometallic reagents to the functionalized ketoamides elaborated from dihydroxyacetone dimer for the stereoselective construction of the key quaternary carbon center in the target compound. 相似文献
4.
H. Etori H. Hirata Y. Yamada H. Okabayashi M. Furusaka 《Colloid and polymer science》1997,275(3):263-273
Potassium salts of N-decanoylglycine and N-decanoyl-L-alanine oligopeptides (monomer, dimer and trimer) were synthesized.
For these oligomer salts in aqueous solutions, the microstructures of micelles have been investigated by small-angle neutron-scattering
(SANS). In the calculation of SANS intensity data, the thickness of the hydrophilic layer was altered by changing the conformation
of the oligomer moiety (helical and β-sheet structures). For micelles of the trimer salts, the helical structure models provide
the best fit to the observed SANS intensity data. For micelles of the monomer-and dimer-salts, the β-sheet model provides
the best fit to the observed data. For the monomer-and dimer-micelles, the aggregation number (n) is not dependent on the species of amino acid residue, imply-ing that the decanoyl group plays a critical role in micelle
formation. However, for the trimer micelles, the n value is dependent on the species of amino acid residue.
Received: 11 July 1996 Accepted: 11 September 1996 相似文献
5.
Zheng Li Jin-Lan Yu Sheng-Yi Shi Wei Zhu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):1031-1037
A rapid method to N-acyl ureas from corresponding N-acyl thioureas is described. N-coumaroyl-N′-arylthioureas, which are easily prepared by the reaction of coumarin-3-carboxylic acid chloride with potassium thiocyanate and arylamines, can be expeditiously transformed into corresponding N-acyl ureas via r.t. grinding with wet silica supported potassium permanganate under solvent-free conditions in an excellent yield. 相似文献
6.
Stereoselective total synthesis of two chiral lactones, (+)‐trans‐cognac lactone (1b) and (+)‐trans‐aerangis lactone (2c), has been achieved from the same intermediate using a radical‐based cyclization route. 相似文献
7.
Triflic acid-mediated stereoselective direct lactonization of a variety of α-amino γ,δ-unsaturated carboxylic acid esters and the construction of new γ-butyrolactone structural motifs are reported. Several α-amino γ,δ-unsaturated carboxylic acid esters underwent stereo- and regioselective 1,5-cyclization and afforded a variety of highly substituted homoserine lactone scaffolds having contiguous stereocenters. The direct lactonization of the chiral α-amino γ,δ-unsaturated carboxylic acid esters with triflic acid led to the enantioselective synthesis of the novel homoserine lactones. A plausible mechanism for the direct lactonization of α-amino γ,δ-unsaturated carboxylic acid esters is presented. The stereochemistry of major isomers 3f, 7a, 7b, and 7d was unambiguously established from the X-ray structure analysis. 相似文献
8.
Highly regio- and stereoselective synthesis of glucosylspiro-oxindole/acenaphthenone derivatives was accomplished through 1,3-dipolar cycloaddition (1,3-DC) reaction. The glucosyl α,β-unsaturated-7,3-lactone (a sugar lactone) derived from d-glucose was used as a chiral dipolarophile in 1,3-DC reaction for the first time. The azomethine ylides generated from sarcosine/l-proline/thiazolidine-4-carboxylic acid/piperidine-2-carboxylic acid with isatin and acenaphthoquinone were trapped by the sugar lactone to give a series of glucosylspiro-pyrrolidine derivatives in good yields. 相似文献
9.
Siriphorn Chimplee Sittiruk Roytrakul Suchada Sukrong Theera Srisawat Potchanapond Graidist Kanyanatt Kanokwiroon 《Molecules (Basel, Switzerland)》2022,27(2)
Triple negative breast cancer (TNBC) is a breast cancer subtype characterized by the absence of estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 expression. TNBC cells respond poorly to targeted chemotherapies currently in use and the mortality rate of TNBC remains high. Therefore, it is necessary to identify new chemotherapeutic agents for TNBC. In this study, the anti-cancer effects of 7-α-hydroxyfrullanolide (7HF), derived from Grangea maderaspatana, on MCF-7, MDA-MB-231 and MDA-MB-468 breast cancer cells were assessed using MTT assay. The mode of action of 7HF in TNBC cells treated with 6, 12 and 24 µM of 7HF was determined by flow cytometry and propidium iodide (PI) staining for cell cycle analysis and annexin V/fluorescein isothiocyanate + PI staining for detecting apoptosis. The molecular mechanism of action of 7HF in TNBC cells was investigated by evaluating protein expression using proteomic techniques and western blotting. Subsequently, 7HF exhibited the strongest anti-TNBC activity toward MDA-MB-468 cells and a concomitantly weak toxicity toward normal breast cells. The molecular mechanism of action of low-dose 7HF in TNBC cells primarily involved G2/M-phase arrest through upregulation of the expression of Bub3, cyclin B1, phosphorylated Cdk1 (Tyr 15) and p53-independent p21. Contrastingly, the upregulation of PP2A-A subunit expression may have modulated the suppression of various cell survival proteins such as p-Akt (Ser 473), FoxO3a and β-catenin. The concurrent apoptotic effect of 7HF on the treated cells was mediated via both intrinsic and extrinsic modes through the upregulation of Bax and active cleaved caspase-7–9 expression and downregulation of Bcl-2 and full-length caspase-7–9 expression. Notably, the proteomic approach revealed the upregulation of the expression of pivotal protein clusters associated with G1/S-phase arrest, G2/M-phase transition and apoptosis. Thus, 7HF exhibits promising anti-TNBC activity and at a low dose, it modulates signal transduction associated with G2/M-phase arrest and apoptosis. 相似文献
10.
Schupp PJ Charlton TS Taylor MW Kjelleberg S Steinberg PD 《Analytical and bioanalytical chemistry》2005,383(1):132-137
A challenge for understanding the role of bacterial cell–cell signalling in the environment is the detection of those signals,
which are often present in low (nmol L−1) concentrations. We describe here a simple purification method, solid-phase extraction (SPE), for increasing the sensitivity
of detection for one such group of signals, acyl homoserine lactones (AHLs), in environmental samples. Spiking of dried marine
sponge tissue (Stylinos sp.) with AHLs resulted in detection down to 0.01 ppm for 3-oxo-hexanoyl homoserine lactone (3-oxo C6-HSL) and 1 ppm for hexanoyl homoserine lactone (C6-HSL). Compared with liquid extraction methods use of SPE resulted in twofold and tenfold improvements in sensitivity, respectively. 相似文献