Fluvirosaones A and B, Two Indolizidine Alkaloids with a Pentacyclic Skeleton from <i>Flueggea virosa</i>

Fluvirosaones A (<b>1</b>) and B (<b>2</b>), together with virosecurinine (<b>3</b>), were isolated from <i>Flueggea virosa</i>. Their structures were determined by physical, spectroscopic, and X-ray analysis and confirmed through comparison of the calculated and experimental ¹³C NMR and electronic circular dichroism (ECD) data. Compounds <b>1</b> and <b>2</b> represent the first examples of a pentacyclic <i>Securinega</i> alkaloid containing a pentacyclic system and an α,β-unsaturated ketone. Plausible biogenetic pathways of compounds <b>1</b> and <b>2</b> are proposed