New Verticillane Diterpenoids from Cespitularia taeniata

Chemical investigation of Cespitularia taeniata has led to the isolation of three new verticillanes, cespitulins E–G (1–3, resp.). The structures of these compounds were elucidated by spectroscopic analysis, especially HR‐MS and 2D‐NMR techniques. Compound 1 possesses a rare norverticillane skeleton with two adjacent OH groups at C(5) and C(6), while the seco‐compound 2 with an aldehyde group at C(9) results from an unusual bond cleavage between C(9) and C(10). Pharmacological studies revealed that compound 3 exhibited significant activities on superoxide‐anion generation and elastase release by human neutrophils in response to FMLP/CB. A plausible biogenetic pathway for compound 2 is also discussed.