An Efficient Synthesis of (±)-Dehalo­perophoramidine

Perophoramidine
and communesin F are structurally related indole
alkaloids with an intriguing polycyclic core containing vicinal all-carbon
quaternary stereocenters. Dehalopero­phoramidine is a dehalogenated
synthetic analogue of perophoramidine. Synthetic studies toward the
total synthesis of dehalopero­phoramidine have led to the discovery
of two novel domino processes, the first encompassing four steps and
resulting in the formation of an ortho-amide. A thorough
study of the reactivity of the ortho-amide functionality
revealed the second domino reaction and ultimately yielded the target
molecule. The vicinal all-carbon quaternary stereocenters having trans relative stereochemistry are constructed early in
the reaction sequence by employing Overman’s samarium mediated
reductive dialkylation procedure. Described are the synthetic studies
that led to the final eight-step synthesis of dehalopero­phoramidine.