New acyclic sesquiterpenes and norsesquiterpenes from the Caribbean gorgonian Plexaurella grisea

The gorgonian Plexaurella grisea from Punta Cana, Dominican Republic, conta ins five new acyclic sesquiterpenes, (3E,5E)-3,7,11-trimethyl-9-oxododeca-1 ,3,5-triene (3), (3Z,5E)-3,7,11-trimethyl-9-oxododeca1,3,5-triene (4), (3E) -6-acetoxy-3,11-dimethyl-7-methylidendodeca- 1,3,10-triene (5), (3E,SE)-7-h ydroxy- 3,7,11-trimethyldodeca-1,3,5,10-tetraene (6), and (3E,5E,9E)-8, 11- diacetoxy-3,7,11-trimethyldodeca-1,3, tetraene (7), and two new linear nors esquiterpenes, (2E,4E,7Z)-2,6,10-trimethylundeca-2,4,7, (8) and (2E,4E)-2,6 ,10-trimethylundeca-2,4,9-trienal (9), in addition to the known compounds 1 , 2, and 10. The structures of the new compounds 3-9 were elucidated by int erpretation of spectroscopic data. En general, the new compounds are mildly cytotoxic against tumor cell lines, and although norsesquiterpene 8 was in active, norsesquiterpene 9 exhibited the greatest and selective activity ag ainst the P-388 tumor cell line.