Total synthesis and structural revision of engelhardione.

The total synthesis of the macrocyclic natural product engelhardione is reported. This effort led to the structural revision of the published structure of engelhardione to that of pterocarine. The revision reflects the change of the substitution pattern of one phenyl ether ring from the meta to the para position. To confirm, pterocarine (2) and its close regioisomer 3 were subsequently synthesized for comparison. Moreover, to the best of our knowledge, our synthesis of 1 represents the first example of a 14-membered macrocyclic diarylheptanoid with a meta-meta substitution pattern at the diphenyl ether moiety.