Dictamins A–C, three unprecedented apotirucallane-type trinortriterpenoids from Dictamnus dasycarpus

Dictamins A–C, the first known examples of apotirucallane-type trinortriterpenoids, were isolated from the root bark of Dictamnus dasycarpus . Their structures and relative configurations were elucidated on the basis of extensive NMR and single-crystal X-ray diffraction analyses. Such compounds might be the key C 5 side chain intermediates for an alternative degradation process from protolimonoids (C 8 side chain) to limonoids (C 4 side chain), bridging an oxidative cleavage biogenetic pathway between these two classes of structurally diverse triterpenoids.