Spiroplakortone, an unprecedented spiroketal lactone from the Chinese sponge Plakortis simplex

Abstract

A new polyketide-based metabolite, spiroplakortone (1), characterized as an unprecedented γ-spiroketal-γ-lactone, was obtained from the Chinese sponge Plakortis simplex. Structural characterization of spiroplakortone (1) was based on extensive spectroscopic analysis and its configuration was partly established by GIAO ¹³C-NMR, supported by DP4 probability analysis, and ECD calculations. A plausible pathway for the biosynthesis of spiroplakortone (1), envisaging the formation of a carbon–carbon linkage between polyketide and aminoacid (leucine)-derived moieties, has been proposed.