Catalytic, asymmetric transannular aldolizations: total synthesis of (+)-hirsutene.

We report an asymmetric, catalytic transannular aldolization that provides polycyclic products useful for natural product synthesis. We found that a proline-derivative catalyzes the transannular aldol reaction of 1,4-cyclooctanediones to the corresponding cyclic beta-hydroxy ketones in good yields and with high enantioselectivities. The utility of our reaction has been demonstrated in a total synthesis of (+)-hirustene.