title: A protecting group free synthesis of (+/-)-neostenine via the [5 + 2] photocycloaddition of maleimides.
abstract: A concise, linear synthesis of the Stemona alkaloid (+/-)-neostenine is reported. Key features include an organocopper-mediated bislactone C2-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.
authors.affiliation: School of Chemistry, Cantock's Close, University of Bristol, Bristol BS8 1TS, UK.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Lainchbury
authors.forename: Marcus I
authors.initials: MI
authors.lastname: Medley
authors.forename: Piers M
authors.initials: PM
authors.lastname: Taylor
authors.forename: Paul
authors.initials: P
authors.lastname: Hirst
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Dohle
authors.forename: Kevin I
authors.initials: KI
authors.lastname: Booker-Milburn
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis*; D001381:Azepines / Q000737:chemistry; D003510:Cyclohexanes / Q000737:chemistry; D005663:Furans / Q000737:chemistry; D007783:Lactones / Q000737:chemistry; D008301:Maleimides / Q000737:chemistry*; D008956:Models, Chemical; D010777:Photochemistry; D011758:Pyrroles / Q000737:chemistry; D041901:Stemonaceae / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D001381:Azepines; D003510:Cyclohexanes; D005663:Furans; D007783:Lactones; D008301:Maleimides; D011758:Pyrroles; C441784:stenine; C043592:maleimide; C506365:Cyclohexane