Total Syntheses of (±)-Isosteviol and (±)-Beyer-15-ene-3β,19-diol by Manganese(III)-Based Oxidative Quadruple Free-Radical Cyclization
摘要:
Tetraene 1 was prepared in nine steps from the known propargylic alcohol 7 in 17% overall yield or as a 2:1 E/Z mixture in only five steps in 7% overall yield. Oxidative cyclization of 1 with 2 equiv of Mn(OAc)(3). 2H(2)O and 1 equiv of Cu(OAc)(2) in MeOH at 25 degrees C provided 35% of tetracycle 2. Further elaboration provided (+/-)-isosteviol (3) in six steps in 51% yield and (+/-)-beyer-15-ene-3 beta,19-diol in four steps in 17% yield.
Highly stereoselective synthesis of exocyclic alkenes via cyclialkylation
作者:Ei-ichi Negishi、Yantao Zhang、Vahid Bagheri
DOI:10.1016/s0040-4039(01)81055-8
日期:1987.1
Treatment of stereodefined ω-halo-2-iodoalkene derivatives (1), prepared viastereoselective addition reactions of alkynes, with either -BuLi (1 equiv) or -BuLi (2 equiv) can produce exocyclicalkenes whose isomeric purity is essentially 100%.