Cyclobutastellettolides A and B, C₁₉ Norterpenoids from a <i>Stelletta</i> sp. Marine Sponge

Abstract

Two novel C₁₉ terpenoids (<b>1</b>, <b>2</b>) with an unprecedented carbon skeleton (<b>A</b>) were isolated from a <i>Stelletta</i> sp. sponge collected from Vietnamese waters. Their structures and absolute configurations were established by extensive NMR, MS, and ECD analyses together with quantum chemical modeling and biogenetic considerations. The probable pathways of biogenesis of <b>1</b> and <b>2</b> from isomalabaricane triterpenoids are discussed. Compounds <b>1</b> and <b>2</b> significantly increase the production of reactive oxygen species in murine peritoneal macrophages.