Programmed serial stereochemical relay and its application in the synthesis of morphinans

Herein we report a rationally designed, serial point-to-axial and axial-to-point stereoinduction and its integration into multi-step and target-oriented organic synthesis. In this proof-of-concept study, the configurational stability of several carefully designed atropisomeric intermediates and the fidelity of their unconventional stereoinductions were systematically investigated. The highly functionalized prepared synthetic intermediate was further applied in a novel chemical method to access the morphinans and it is potentially applicable to other structurally related alkaloids.

Rapid construction of the 6/6/5 tricyclic framework via a tandem radical cyclization reaction and its application to the synthesis of 5-epi-7-deoxy-isoabietenin A

A tandem radical cyclization towards the 6/6/5 tricyclic skeleton, which exists in numerous natural products, was developed in modest to good yields.

Divergent enantioselective synthesis of (-)-galanthamine and (-)-morphine

An efficient divergent synthetic strategy for the synthesis of the opiate and amaryllidaceae alkaloids emerges by employing a Pd-catalyzed asymmetric allylic alkylation (AAA) to set the stereochemistry. Three generations of syntheses of galanthamine are discussed in detail with particular focus on the scope of the palladium-catalyzed AAA reactions and intramolecular Heck reactions. The pivotal tricyclic intermediate is available in six steps from 2-bromovanillin and the monoester of methyl 6-hydroxycyclohexene-1-carboxylate. This intermediate requires only two steps to convert to (-)-galanthamine. Using a Heck vinylation, we found that the fourth ring of codeine/morphine could be formed. The final ring formation involves a novel visible light-promoted hydroamination. Thus, six steps are required to convert the pivotal tricyclic intermediate into codeine, which has been demethylated in high yield to morphine.