ISOLATION AND CHARACTERIZATION OF THE ACTIVE PRINCIPLE OF ELEPHANTOPUS CAROLINIANUS AND APPROACHES TO THE SYNTHESIS OF SESQUITERPENE LACTONES.

摘要

Isolation and characterization of the active principle of Elephantopus carolinianus is described. Ground plant was extracted with 95% ethanol using a soxhelet apparatus. The concentrate was partitioned between chloroform and water. The chloroform layer was concentrated and partitioned between petroleum ether and aqueous methanol. The alcohol layer was concentrated, freeze-dried, and chromatographed on silica gel with benzene, benzene-chloroform mixtures, chloroform, and 10% methanolic chloroform as eluents. By spectral data (UV, IR, Mass Spectra, PMR, and CMR) and elemental analysis, the compound was identified as deoxyelephantopin. An error in the NMR data reported by Lee, Cowherd, and Wolo was noted.; Two approaches to eudesmanolides are outlined. 3-Butylthio-2-cyclohexenone was alkylated first with methyl iodide, then with 1,3-dichloro-2-butene. The sulfoxide was then formed and displaced with t-butyl sodiocyanoacetate. Hydrolysis of the vinylchloride, followed by cyclo-dehydration of the diketone gave 7-cyanomethyl-10-methyl-1(9),7(8)-hexalin-2-one, a promising sesquiterpenoid intermediate. Alternatively 6-methyl-3-butylthio-2-cyclohexenone was alkylated with 1-bromo-2-pentyne. The resulting alkyne was then examined as an alternate intermediate.; The second sequence involves the reaction of enamines with alkyl pentadienoates. The best A-ring precursor--the enamine of 2-methyl-5-ethylenedioxyheptanal, was synthesized from ethyl vinyl ketone and diethyl methylmalonate via saponification, decarboxylation, esterification, ketalization, reduction, and oxidation. The 3-substituted 2,4-pentadienoates were made by vinyl cuprate addition to 3-substituted alkyl propiolates or dialkyl alkoxymethylenemalonates. 1-Pyrrolidino-cyclohexene was heated in the presence of ethyl 3-(2-1-ethoxyethoxy) ethyl)-2,4-pentadienoate or ethyl 2-carbethoxy-2,4-pentadienoate to give 1,4-addition products.