Total Synthesis and Structural Revision of the Piperarboreeines: When Photochemistry Meets C-H Activation

摘要

The piperarborenines, isolated from the stems of the creeping shrub Piper arborescens, are members of a class of quasi-dimeric monoterpene alkaloids characterized by a tetrasubstituted cyclobutane ring. Closely related to the piperarborenines, but structurally more complex, is the incarvillateine family of natural products, in which the dihydropyridone is replaced by an elaborate bicyclic piper-idine moiety containing five contiguous stereocenters (Figure 1). Interestingly, structure-activity relationship studies performed on 3 and derivatives thereof suggest that the cyclobutyl moiety plays a crucial role in the expression of biological activity.