Spiroamentotaxols A–D: unprecedented 6/6/6/5/6/6/6/6 spiro-octacyclic bis-diterpene heterodimers from the endangered conifer Amentotaxus yunnanensis and their bioactivities

A new chemical class of 6/6/6/5/6/6/6/6 spiro-octacyclic Diels–Alder [4 + 2] heterodimers ( ent -kaurene and norabietane) was isolated and characterized from Amentotaxus yunnanensis . They exhibited in vitro anti-inflammatory and anticancer activities.