The Absolute Configurations and Biogenesis of Some New Halogenated Chamigrenes from the Sea Hare Aplysia dactylomela

✍ Scribed by Ryuichi Sakai; Tatsuo Higa; Charles W. Jefford; GéRald Bernardinelli

• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: German
• Weight: 857 KB
• Volume: 69
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19860690113

✦ Synopsis

Four new halogenated chamigrenes have been isolated from the sea hare, the (E)-and (Z)-9-(bromomethylidene)-1,2,5-trimethylspiro[5.5]undeca-l,7-dien-3-ones (11 and 10, resp.) the structures of which were deduced by NMR spectroscopy and by comparison with a known relative, the (8R,9R)-8-bromo-9-chloro-5,5,9-trimethyl-lmethylidenespiro[5,5]undec-3-en-2-one (12), and its (1 1 R)-1 I-acetoxy-substituted derivative 13. Their structures and absolute configurations were determined and deduced by X-ray using the absolute-structure parameter. The configurations were remarkable in being enantiomeric to those of the tertiary chlorochamigrenes isolated so far. Consequently, a more general scheme is proposed to account for their biogenesis.

Introduction. -The algal genus Laurencia, a red sea weed, i s a rich source of halogenated sesquiterpenes [l]. Ever since the discovery of pacifenol (l), a tricyclic chamigrene structure, in 1971 [2], some 25 other chlorobromochamigrenes have been isolated from