The Total Syntheses of Guttiferone A and 6-epi-Guttiferone A

Polyprenylated polycyclic acylphloroglucinols (PPAP) are a constantly growing class of natural products that exhibit a common bicyclo[3.3.1]­nonatrione core and consist of currently more than 200 members. A subclassification among the various natural products of this class includes the position of the exocyclic acyl group, the prenylation grade of the core, and the relative configuration at C-7 within the core. About 10% of the reported structures, however, possess an additional chiral center at C-6. Herein we describe a straightforward access to guttiferone A and epi-guttiferone A, in which full control of stereoselectivity is achieved via conformational control, and a strict separation of framework decorating from framework constructing operations sets the stage for a short 13-step synthesis.