Application of an intramolecular dipolar cycloaddition to an asymmetric synthesis of the fully oxygenated tricyclic core of the stemofoline alkaloids

An intramolecular non-stabilized azomethine ylide dipolar cycloaddition was applied toward the first non-racemic synthesis of the fully oxygenated bridged pyrrolizidine core (45) of (+)-stemofoline (1) in 11 steps from a commercially available starting material.