Skeleton Reassignment of Type C Polycyclic Polyprenylated Acylphloroglucinols.

The previous assignment of the type C skeleton of polycyclic polyprenylated acylphloroglucinols (PPAPs) was controversial and proved to be incorrect in this study. The structures of the type C PPAPs (3-6) were revised to corresponding type A structures (3a-6a) via 13C NMR spectroscopic analysis and a quantum computational chemistry method. Therefore, only types A and B PPAPs are likely present in plants of the family Clusiaceae.