(A) Selected members of eunicellane diterpenoids. The 6/10-bicyclic eunicellane skeleton possesses either cis or trans ring configuration and is found in coral, bacteria, and plants. The trans ring fusion is rare in known natural products.
(B) Recent studies support mechanistic differences between two cis-eunicellane di-TSs, Bnd4 from Streptomyces sp. (CL12–4) and EcTPS1 from Erythropodium caribaeorum. Prior to this study, no TSs that form the trans-eunicellane skeleton were known.