Isolation of Scalarane-type Sesterterpenoids from the Marine Sponge Dysidea sp. and Stereochemical Reassignment of 12-epi-phyllactone D/E

Abstract

Sixteen new scalarane based sesterterpenoids (1–16), together with fourteen known compounds were characterized from the marine sponge dysidea sp., which was collected from Bohol province in Philippines. The chemical structures of compounds 1–16 were elucidated on the basis of combined 1D/2D NMR and HRMS spectroscopic data. The structure of the bishomoscalarane 15 isolated during this study was claimed to be characterized in 2007. However, inspection of our experimental 13C NMR spectrum revealed considerable discrepancies with the reported data at C-9, C-12, C-14, and C-23, leading to correction of the reported compound into the known mixture of phyllactone D and E. Biological properties of 1–16 were evaluated utilizing MDA-MB-231 cancer cell line. As a result, compound 7 that bears a pentenone E-ring exhibited a significant cytotoxicity with a GI50 value of 4.21 uM. Detailed studies to elucidate the biological mechanism of 7 are currently underway.