C=C1[C@@H](OC(C)=O)[C@H]2[C@]3(C)C=CC(=O)C(C)(C)[C@H]3C(=O)[C@]3(O)OC4=C(C)OC(=O)[C@@]1(C)[C@]4(C(=O)OC)[C@]23C furanasperterpene A