Several tetrahydrofuran lignans have become important due to their diverse biological activities. We present initial studies on short syntheses of some of the simplest members of this natural product class. Galgravin and Veraguensin are obtained in only three or four steps from nitroalkenes and allylic alcohols via a new tandem anionic-radical process, and reductive radical cyclizations of beta-nitro ethers derived from the same precursors are suitable to obtain Galgravin as well as Galbelgin and Ganschisandrin.
The synthesis of highly functionalized 3-nitrotetrahydrofurans starting from allylic alcohols and nitroalkenes through an efficient CuCl 2 -mediated tandem anionic/radical process is reported. The one-pot reaction consists of oxa-Michael addition/SET/radical 5-exo-cyclization-ligand transfer. Functionalization of the THF ring is facile and provides diverse substituted derivatives.
The tandem reactions which consist of conjugate addition of alkoxides to nitroalkenes and radical 5‐exo cyclizations are a convenient strategy to obtain functionalized tetrahydrofurans in a single step.
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