Biomimetic synthesis of hyperjapones F-I

Abstract

Hyperjapones F–I are tetracyclic meroterpenoids recently isolated from Hypericum japonicum. All four of these natural products have been synthesised using oxidative, intermolecular hetero-Diels–Alder reactions to couple their common biosynthetic precursor, norflavesone, to the appropriate monoterpene building blocks: sabinene, β-pinene, and α-pinene. The synthesis of enantiomerically pure hyperjapones H and I and comparison of their optical rotations to those of the natural samples indicated that these meroterpenoids are probably biosynthesised as either racemic or scalemic mixtures.