Palladium (II) catalyzed 5-endo epoxynitrile cyclizations: total syntheses of enokipodins A and B

A new divergent total synthesis of the cuparenic sesquiterpenes enokipodins A and B is described. It features as the key step a novel cation-controlled, palladium (II) improved, 5-endo cyclization, which has been classically considered as 'non-favoured'.