Chartspiroton, a Tetracyclic Spiro-naphthoquinone Derivative from a Medicinal Plant Endophytic <i>Streptomyces</i>

Abstract

A novel 6/6/5/6 tetracyclic polyketide named chartspiroton (<b>1</b>) was isolated from a medicinal plant endophytic <i>Streptomyces</i> in <i>Dendrobium officinale.</i> The complete structure assignment with absolute stereochemistry was elucidated through spectroscopic data, computational calculations, and single-crystal X-ray diffraction. Chartspiroton features an unprecedented naphthoquinone derivative spiro-fused with a benzofuran lactone moiety. A plausible polyketide biosynthetic pathway for <b>1</b> suggested intriguing oxidative rearrangement steps to form the five-membered lactone ring.