Nitrogen-Containing Diterpenoids, Sesquiterpenoids, and Nor-Diterpenoids from Cespitularia taeniata

Two new nitrogen-containing verticillene diterpenoids, cespilamides A and B (1 and 2), three new nitrogen-containing sesquiterpenoids, cespilamides C–E (3–5), and five new norverticillene and verticillene diterpenoids, cespitaenins A–E (6–10), were isolated from the Taiwanese soft coral Cespitularia taeniata. Compound 1 possesses an unusual oxazo ring system at C-10 while compound 2 displays an unprecedented C–C bond cleavage between C-10 and C-11 with an N-ethylphenyl group at C-10. Biogenetic pathways of 1 and 2 are proposed. The absolute configuration of 1 was confirmed by Mosher’s method and molecular mechanics calculations (MM2). The cytotoxicities of compounds 1–10 were evaluated against a small panel of human cancer cell lines