NEW CYTOTOXIC BRIARAN DITERPENES FROM THE FORMOSAN GORGONIAN BRIAREUMSP

Three new briaran diterpenes, 2 beta-acetoxy-2-(debutyryloxy) stecholi de E (3), 9 -deacetylstylatulide lactone (4), and 4 beta-acetoxy-9-dea cetylstylatulide lactone (5), and two known diterpenes, brianthein W ( 1) and 9-deacetylbriareolide H (2), have been isolated from a Briareum sp. of gorgonian. The structures and relative stereochemistry of thes e compounds were determined by spectroscopic and chemical methods. Dit erpenes 2-4 and the corresponding 9-acetyl derivatives 6, 7, and 12 ex hibited cytotoxicity toward various cancer cell lines.