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951.
Guang-Ying Chen Bin Zhang Ting Zhao Najat Nidhal Wang Jia-Li Xue-Ming Zhou 《Natural product research》2020,34(13):1874-1878
AbstractA new triterpenoid glucoside, leuctriterpencoside (1), along with two known compounds (2–3) were isolated from Leucas zeylanica. The structure of the new compound was elucidated using comprehensive spectroscopic methods. Compound 1 showed significant inhibitory activity against α-glucosidase (IC50 value of 0.85?±?0.12?μM). 相似文献
952.
STUDYONTHESEPARATIONOFGLUTAMICACIDBYION-EXCHANGEShenJinyu;WangQinyu(DepartmentofChemicalEngineering,TsinghuaUniversity,Beijin... 相似文献
953.
腐植酸与苯乙烯的接枝共聚改性 总被引:4,自引:0,他引:4
研究了腐植酸(HA)与苯乙烯(St)以H_2O_2-FeCl_2为引发体系的接枝共聚。结果表明,HA对St聚合有阻聚及滞聚作用。接枝度在H_2O_2/FeCl_2=3(摩尔比)时有极大值,提高聚合温度可使接枝效率和接枝度同时增加、增加St-HA的用量比可使接枝度增加,但接枝效率降低,接枝比基本不变。由接枝共聚物的红外光谱分析得出HA与PSt是以C-O-C连接的。接枝共聚物的磺化产物在水和酸性介质中均能溶解。 相似文献
954.
IINTRODUCTIONChiralphosphinesareveryusefulligandsinenantioselectivecatalysiswithtransitionmetalcomplexes"'.Becausesugarisrichnotonlyinstereochemistrybutalsoinnatureandpossessesmanyhydroxylgroupsassyntheticstartingpoints,theyhavereceivedmuchattentionsincethe1970st2i.However,thetypesofchiralphosphinesinwhichthephosphorusatomsareattacheddirectlytothesecondarycarbonsofsugararefew.Thedifficultiesinthesyntheticprocessesarepartofthereason.Bythenucleophilicreplacementreaction,itisdifficulttolink… 相似文献
955.
Reaction of phenylsulfonyl formamides, readily available in a single step from an aromatic aldehyde and sodium phenylsulfinate, with ketene diethyl acetal under basic conditions gives N-formyl β-amino acid esters in good yield, which can be kinetically resolved with a lipase. 相似文献
956.
《Arabian Journal of Chemistry》2022,15(11):104189
The quality of grains is influenced by storage pests, which are not only spoilers of stored grain, but also vectors of human and animal diseases. Chemical pesticides play an essential role in the cultivation and storage of cereals, however, due to the low degradability and residual toxicity of synthetic pesticides on the environment and non-target organisms, as well as the increasing resistance of target organisms to them, consideration should be given to the development of alternative pest control agents. Compounds isolated from natural sources have emerged as preferred targets for the development of novel insecticidal agents because of their eco-friendliness, safety, and effectiveness. In this review, we primarily focus on the natural product (NPs) control of storage pests. The effective monomer components of NPs and their anti-insect mechanisms were discussed, and natural sources of inspiration and models for insect repellents are described. This review aimed to provide guidelines for the exploitation and utilization of green and efficient natural insecticides. 相似文献
957.
Ipsita RoyMunishwar N. Gupta 《Tetrahedron》2003,59(29):5431-5436
The non-thermal effects of microwave irradiation on enzyme-catalyzed reactions have been evaluated by keeping the reaction temperature constant during irradiation. Subtilisin-catalyzed transesterification and α-chymotrypsin-catalyzed esterification have been carried out in six solvents of differing polarities and at three different temperatures. In all cases, microwave irradiation was found to increase the initial reaction rates by 2.1-4.7 times at all hydration levels. It is also shown that microwave irradiation can be used in conjunction with other strategies (like pH tuning and salt activation) for enhancing initial reaction rates. 相似文献
958.
Yung-Son Hon Tzyy-Rong HsuChun-Yan Chen Yi-Hui LinFong-Jong Chang Cheng-Han HsiehPing-Hui Szu 《Tetrahedron》2003,59(9):1509-1520
The reactivity of aryl alkyl ketone with a preheated mixture of dibromomethane and diethylamine is poor and gives an α-methylenation product in very low yield even under refluxing condition. It can be accelerated dramatically by microwave irradiation. Under microwave condition, the cyclic 1,3-dicarbonyls, aryl alkyl ketones, heteroaryl alkyl ketones and acyclic benzyl ketone give α-methylenation products in modest to good yields. 相似文献
959.
960.
F. Bredice H. Sobral M. Villagran-Muniz H.O. Di Rocco G. Cristoforetti S. Legnaioli V. Palleschi A. Salvetti E. Tognoni 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
A Nd:YAG laser pulse was focused, in air or on a Cu target, between the plates of a planar charged capacitor. The plasma generates a transient redistribution of the electrical charges on the plates that can be easily measured as a voltage drop across a resistor connected to the ground plate. At the same time, the Stark broadening of the Hα spectral line (656.3 nm) obtained from the optical emission spectrum of the plasma was measured. In this work, we show that the peak of electrical signal measured on the resistor is, in the energy range of our laser (30 mJ to 220 mJ) and at time delays typical of Laser-Induced Breakdown Spectroscopy applications (500–5000 ns), univocally related to the temporal evolution of the Stark broadening of the Hα line. Therefore, after a proper calibration depending on the material and the experimental geometry, the peak of the electrical signal can be used to predict the temporal evolution of the electron density of the generated plasma. 相似文献