Cipadonoids B–G, six new limonoids from Cipadessa cinerascens

Six new rings B,D-seco-type limonoids, cipadonoids B–G (1–6) were isolated from leaves of Cipadessa cinerascens. Their structure was elucidated by extensive spectroscopic methods, and that of 1 was confirmed by single-crystal X-ray diffraction. The absolute configuration of compounds (2–6), a class of cipadesin-type limonoids, was determined by CD exciton chirality method and chemical means, representing the first report of assignment of absolute configuration of such type compounds; a biosynthetic pathway of 2–6 was proposed and confirmed by chemical correlation and computational result. Compound 1 showed weak in vitro activity at the insect nicotinic acetylcholine receptor (nAChR).