排序方式: 共有68条查询结果,搜索用时 46 毫秒
21.
Monasnicotinates A-D, four new pyridine alkaloids from the fungal strain Monascus pilosus BCRC 38093
Wu MD Cheng MJ Yech YJ Chen YL Chen KP Chen IS Yang PH Yuan GF 《Molecules (Basel, Switzerland)》2011,16(6):4719-4727
Four new pyridine derivatives, monasnicotinates A-D (1-4) were isolated from the red yeast rice of Monascus pilosus BCRC 38093. Their structures were elucidated on the basis of physicochemical evidence, in-depth NMR spectroscopic analysis, and high-resolution mass spectrometry. Their inhibitory effects on NO production was also evaluated. 相似文献
22.
23.
Ming-Jen Chen 《Tetrahedron letters》2007,48(36):6271-6274
Acylsilanes with latent α-acylamino radical functionality were prepared from different chiral templates. Radical cyclizations of these acylsilanes efficiently constructed polyhydroxylated indolizidine derivatives with excellent stereoselectivity at the bridgehead position. These cyclization products were converted to (+)-lentiginosine, (+)-1,8a-di-epi-lentiginosine, and (+)-1,2-di-epi-swainsonine. 相似文献
24.
Wang I-Chou Chen Li-Chai Chang Tsung-Hsien Chen Chun-Lin Sung Ping-Jyun Lin Rong-An Cheng Ming-Jen Hsiao Jen-Wen Chen Jih-Jung 《Chemistry of Natural Compounds》2021,57(5):835-839
Chemistry of Natural Compounds - A new coumarin derivative, 7-O-methylparamicoumarin A (1), has been isolated from the roots of Chionanthus retusus, together with seven known compounds. The... 相似文献
25.
26.
27.
Ueng SH Chen MJ Chu SF Shao YF Fan GT Chang SY Tsai YM 《The Journal of organic chemistry》2006,71(4):1502-1512
Alpha-tributylstannyl radicals can be generated from the corresponding bromides or xanthates. These radicals undergo efficient intramolecular 1,5-cyclizations with a formyl group. The resulting beta-stannyl alkoxy radicals proceed through a 1,3-stannyl shift from carbon to oxygen to afford beta-stannyloxy radicals. This novel rearrangement is most likely irreversible and serves as a driving force to promote the cyclizations. Although the cyclization rates can be accelerated when the formyl group carries alpha-dimethyl substituents, unfortunately beta-scission of the alkoxy radicals becomes competitive with the 1,3-stannyl shift. The beta-stannyloxy radicals can be employed in further cyclizations to obtain tandem cyclization products. 相似文献
28.
Jyh-Ming Hwu Ming-Jen Chang Jui-Chi Lin Hsiu-Yu Cheng George-J Jiang 《Journal of organometallic chemistry》2005,690(26):10601-6308
This investigation attempts to elucidate the copolymerization reaction ethylene and p-methylstyrene via the homogeneous metallocene catalyst, Et(Ind)2ZrCl2. With increasing of p-methylstyrene concentration, the poly[ethylene-co-(p-methylstyrene)] copolymer shows systematical decrease of melting temperature and crystallinity and increase of glass transition temperature. The benzylic protons of p-methylstyrene are ready for numerous chemical reactions, such as halogenation and oxidation, which can introduce functional groups at the p-methyl group position under mild reaction conditions. With the bromination reaction of poly[ethylene-co-(p-methylstyrene)], polyethylene graft copolymers, such as polyethylene-g-poly(methyl methacrylate) and polyethylene-g-polystyrene can be prepared via atomic transfer radical polymerization. The following selective bromination reaction of p-methylstyrene units in the copolymer and the subsequent radical graft-from polymerization were effective methods of producing polymeric side chains with well-defined structure. The products were characterized by nuclear magnetic resonance, gel-permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis. Additionally, the morphology of PE/PMMA and PE/PMMA/PE-g-PMMA blend are compared by using scanning electron microscope. 相似文献
29.
Ming-Jen Chen Ya-Ting Liu Chiao-Wen Lin Vinoth Kumar Ponnusamy Jen-Fon Jen 《Analytica chimica acta》2013
This paper describes the development of a novel, simple and efficient in-tube based ultrasound-assisted salt-induced liquid–liquid microextraction (IT-USA-SI-LLME) technique for the rapid determination of triclosan (TCS) in personal care products by high performance liquid chromatography-ultraviolet (HPLC-UV) detection. IT-USA-SI-LLME method is based on the rapid phase separation of water-miscible organic solvent from the aqueous phase in the presence of high concentration of salt (salting-out phenomena) under ultrasonication. In the present work, an indigenously fabricated home-made glass extraction device (8-mL glass tube inbuilt with a self-scaled capillary tip) was utilized as the phase separation device for USA-SI-LLME. After the extraction, the upper extractant layer was narrowed into the self-scaled capillary tip by pushing the plunger plug; thus, the collection and measurement of the upper organic solvent layer was simple and convenient. The effects of various parameters on the extraction efficiency were thoroughly evaluated and optimized. Under optimal conditions, detection was linear in the concentration range of 0.4–100 ng mL−1 with correlation coefficient of 0.9968. The limit of detection was 0.09 ng mL−1 and the relative standard deviations ranged between 0.8 and 5.3% (n = 5). The applicability of the developed method was demonstrated for the analysis of TCS in different commercial personal care products and the relative recoveries ranged from 90.4 to 98.5%. The present method was proven to be a simple, sensitive, less organic solvent consuming, inexpensive and rapid procedure for analysis of TCS in a variety of commercially available personal care products or cosmetic preparations. 相似文献
30.
Hao-Chiun Chang Shih-Wei Wang Chin-Yen Chen Tsong-Long Hwang Ming-Jen Cheng Ping-Jyun Sung Kuang-Wen Liao Jih-Jung Chen 《Molecules (Basel, Switzerland)》2020,25(24)
Qin Pi (Fraxinus chinensis Roxb.) is commercially used in healthcare products for the improvement of intestinal function and gouty arthritis in many countries. Three new secoiridoid glucosides, (8E)-4′′-O-methylligstroside (1), (8E)-4′′-O-methyldemethylligstroside (2), and 3′′,4′′-di-O-methyl-demethyloleuropein (3), have been isolated from the stem bark of Fraxinus chinensis, together with 23 known compounds (4–26). The structures of the new compounds were established by spectroscopic analyses (1D, 2D NMR, IR, UV, and HRESIMS). Among the isolated compounds, (8E)-4′′-O-methylligstroside (1), (8E)-4′′-O-methyldemethylligstroside (2), 3′′,4′′-di-O-methyldemethyloleuropein (3), oleuropein (6), aesculetin (9), isoscopoletin (11), aesculetin dimethyl ester (12), fraxetin (14), tyrosol (21), 4-hydroxyphenethyl acetate (22), and (+)-pinoresinol (24) exhibited inhibition (IC50 ≤ 7.65 μg/mL) of superoxide anion generation by human neutrophils in response to formyl-L-methionyl-L-leuckyl-L-phenylalanine/cytochalasin B (fMLP/CB). Compounds 1, 9, 11, 14, 21, and 22 inhibited fMLP/CB-induced elastase release with IC50 ≤ 3.23 μg/mL. In addition, compounds 2, 9, 11, 14, and 21 showed potent inhibition with IC50 values ≤ 27.11 μM, against lipopolysaccharide (LPS)-induced nitric oxide (NO) generation. The well-known proinflammatory cytokines, tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6), were also inhibited by compounds 1, 9, and 14. Compounds 1, 9, and 14 displayed an anti-inflammatory effect against NO, TNF-α, and IL-6 through the inhibition of activation of MAPKs and IκBα in LPS-activated macrophages. In addition, compounds 1, 9, and 14 stimulated anti-inflammatory M2 phenotype by elevating the expression of arginase 1 and Krüppel-like factor 4 (KLF4). The above results suggested that compounds 1, 9, and 14 could be considered as potential compounds for further development of NO production-targeted anti-inflammatory agents. 相似文献