Isolation Of The Chemical Constituents Of Two Compositae And Synthesis Of Benzimidazolyl Complexes And Their Applications In Ethylene Activation

About 80 species belong to the genus Gerbera(Compositae) in the world,of which 20 are distributed in China,mainly in the southwest;only 2 species have been used as Chinese folk medicines with the efficacy of reliving internal heat, antibiotic,reducing phlegm and a cough,invigorating the circulation,diuresis. Gerbera saxatilis is a species of genus Gerbera,which grows on the stone in the Sichuan Province.The Wedelia,consisting of 60 species,is one of the genus in the family Compositae and perennial herbs.The species of Wedelia are mainly distributed in tropical and semitropical zone with 5 species in the southeast and southwest of China.In many countries,the species of Wedelia have long been used for folk medicines with liver protecting,choleretic,antivirus and antiphiogistic efficacy. Wedelia trilobata is a species of genus Wedelia.In the first part of this dissertation,the chemical constituents and their bioactivities of two Compositae species were studied.The chemical constituents were isolated by means of general silica gel column chromatography(CC), preparative thin layer chromatography(PTLC),and recrystallization etc.The structures of these compounds were elucidated by spectroscopic methods,including IR,EI-MS,HR-ESI-MS,¹H-NMR,¹³C-NMR,DEPT,NOSEY,¹H-¹H COSY, HSQC,HMBC,and single-crystal X-ray crystallography.From Gerbera saxatilis,30 compounds were isolated,6 of them are new including 3 benzofuran and 3 coumarin derivatives.From Wedelia trilobata,6 compounds were isolated,1 of them is a new entkaurane-type diterpene. Furthermore the bioactivities of some coumarins were studied,using SRB method to evaluate their cytotoxic activity against human leukemia HL-60 cell,human hepatoma SMMC-7721 cell and human cervical carcinoma HeLa cell.The results would be a supplement for the research on bioactivity of chemical constituents in traditional Chinese medicine,helpful reference for pharmacology, chemotaxonomy and screening new medicines,and may benefit utilizing and developing the natural resources of our country.Finally,recent progress in the development of coumarin derivatives as potent anti-HIV agents was reviewed in this part.The second part of this dissertation focuses on designing and synthesis of benzimidazolyl transition metal complexes as catalysts for ethylene activation.Upon activation with aluminum compounds,these complexes are active for ethylene oligomerization and/or polymerization.The relationship between the ligand environment and the catalytic activity were elucidated.Additionally,the reaction parameters,such as the reaction temperature,cocatalyst,the amount of cocatalyst and ethylene pressure were systemically studied.Two parts are included in this part as follows:Partâ… :A series of N^N^N chromium(â…¢) complexes complexes ligated by 2-imino-6-benzimidazole pyridyl ligands was synthesized and characterized.X-ray crystallographic analysis reveals that the geometry around the chromium atom is octahedral.These tridentate chromium complexes afforded moderate to high activity for ethylene oligomerization and polymerization with broad oligomer distributions from C₄ to C₃₆ and some complexes got special distributions of oligomers.In most cases,polyethylene was the main product and higher carbon number olefins usually accounted for the majority of the oligomers.The obtained polymers were confirmed to be vinyl-terminal long-chain alkenes.Reaction conditions including cocatalyst, temperature,ethylene pressure and reaction time were found to have significant influences on the catalytic behaviors.Partâ…¡:The late transition metal complexes bearing pyridyl benzimidazole ligands were also prepared.Upon treatment with suitable cocatalyst,these complexes showed moderate catalytic activities.