Synthetic studies on isoschizogamine: construction of [3.3.1] bicyclic aminal core by using oxidative skeletal rearrangement

The tetracyclic core structure of isoschizogamine containing aminal functionality was constructed by oxidative skeletal rearrangement of a 1,2-diaminoethene derivative. The 1,2-diaminoethane was prepared by palladium-catalyzed allylation at the 4a position of a 1,2,3,4-tetrahydro-β-carboline derivative and subsequent lactam formation. After the oxidative skeletal rearrangement using dimethyldioxirane, the allyl group was removed by a three-step sequence to provide the tetracyclic core skeleton of isoschizogamine with aminal functionality.