Applanatumols A and B, meroterpenoids with unprecedented skeletons from Ganoderma applanatum

Abstract

Applanatumols A (1) and B [(±)-2], two unique meroterpenoids with a novel spiro[benzofuran-2,2′-bicyclo[3.2.2]nonane] ring system and a naturally unusual dioxacyclopenta[cd]inden motif, respectively, were isolated from Ganoderma applanatum. Their structures were determined using spectroscopic data. In particular, the absolute configurations of 1 and 2 were assigned by X-ray diffraction analysis using the Flack parameter and ECD calculations, respectively. A plausible biosynthetic pathway for 1 and 2 is proposed. The biological activities of 1 and 2 against renal fibrosis were accessed in rat proximal tubular epithelial cells.