A Protecting Group Free Synthesis of (±)-Neostenine via the [5 + 2] Photocycloaddition of Maleimides
作者:Michael D. Lainchbury、Marcus I. Medley、Piers M. Taylor、Paul Hirst、Wolfgang Dohle、Kevin I. Booker-Milburn
DOI:10.1021/jo801108h
日期:2008.9.1
A concise, linear synthesis of the Stemona alkaloid (+/-)-neostenine is reported. Key features include an organocopper-mediated bislactone C-2-desymmetrization for the stereoselective construction of the cyclohexane-lactone C,D-rings. The assembly of the fused pyrrolo[1,2-a]azepine core was achieved by application of a [5 + 2] maleimide photocycloaddition. A custom FEP flow reactor was used to Successfully overcome the scale limitations imposed by a classical immersion well batch reactor. The synthesis was completed in 14 steps from furan, in 9.5% overall yield, without the use of any protecting groups.