An efficient approach to various functionalized alpha-fluoro-alpha-alkynyl esters and gamma-iodoallenoates from available allenoates though a LDA-generated alkynyl enolate intermediate was investigated. The reactions of alkynyl enolates with NFSI in LDA at -80°C for 0.5 hour gave alpha-alkynyl-alpha-fluoro esters in 41-80% yields; while the silyl ether of alkynyl enolate reacted with I2 in EtOH at -80°C for 5 minutes resulted solely the gamma-iodoallenoate in 75% yield.;The bioassay-guided fractionation of the bioactive ethanolic crude extract of a Peruvian medicinal plant, Ambrosia peruviana led to the identification of two compounds. Solvent partition of the extract gave hexanes, dichloromethane and methanol fractions. Upon flash column chromatography of an anticancer cytotoxic dichloromethane fraction, a pseudoguaianolide sesquiterpene lactone was isolated and identified possibly as Damsin. A long chain primary alcohol was obtained from hexanes fraction and identified as 1-Hexadecanol. Several anticancer cytotoxic fractions were also isolated and have potentials for the discovery of anticancer compounds.
展开▼
