In conclusion, successive alkene oxidative cleavage and double Mannich reactions enable the stereoselective transformation of simple norborenes into complex tricyclic alkaloid-like species 10. The approach represents a one-atom ring expansion with simultaneous annulation and permits direct and scalable synthesis of scaffolds which have been shown to undergo three-fold orthogonal reactivity. The compounds also undergo surprisingly regioselective enol triflate formation, with subsequent cross-coupling adding additional scope for subsequent diversification. Further, the scaffold formed is readily converted into scaffold 23, which possesses an unusual 8,5,5-tricyclic architecture and is capable of undergoing similarly broad diversification. Given the high levels of diastereocontrol and that methods for performing asymmetric Diels-Alder reactions are well established, the methodology also offers the potential to access complex, enantioenriched scaffolds. Use of such oxidative cleavage/double Mannich sequences need not be limited to norbornene-derived alkenes, and studies of the scope of this oneatom ring expansion/annulation methodology are underway.