β-Methoxy-γ-methylene-α,β-unsaturated-γ-butyrolactones from Artabotrys hexapetalus

Abstract

The dichloromethane extract of the aerial parts of Artabotrys hexapetalus afforded three β-methoxy-γ-methylene-α,β-unsaturated-γ-butyrolactones, which are proposed to be derived from a C18 unsaturated fatty acid by a biosynthetic route similar to that proposed for the Annonaceous acetogenins. The structure of the unique β-methoxy-γ-methylene-substituted, α,β-unsaturated-γ-butyrolactone ring of artapetalins A–C (1–3) was determined by 2D-NMR spectroscopic analyses. Two unusual simple butyrolactones, (+)-tulipalin B and (2R,3R)- 3-hydroxy-2-methylbutyrolactone were also isolated from this species.