Novel marine polyethers Marı ´a L. Souto, Claudia P. Manrı ´quez, Manuel Norte and Jose ´ J. Ferna ´ndez * Instituto Universitario de Bio-Orga ´nica ‘Antonio Gonza ´lez’, Universidad de La Laguna, Astrofı ´sico Francisco Sa ´nchez 2, 38206 La Laguna, Tenerife, Spain Received 30 May 2002; accepted 26 July 2002 Abstract—The red seaweed Laurencia viridis is a rich source of secondary metabolites derived from squalene. Novel polyethers, clavidol 4, 3-epi-1111-dehydrothyrsiferol 5, and lactodehydrothyrsiferol 6, have been isolated and their structures established by spectroscopical methods. The relative stereochemistry proposed for these compounds is based on ROESY and NOEDIFF data. Possible biogenetic pathways are also discussed. q 2002 Elsevier Science Ltd. All rights reserved. Research into secondary metabolites from marine organ- isms has produced a host of compounds with unique structural features and promising biological activities. 1 Compounds with a polyether moiety, particularly polyether squalene-derived triterpenes, are prime examples of such marine natural products. These metabolites have been found mainly in red algae of the genus Laurencia and in sponges of the Axinellidae family. 2 Analysis of the biological activity of these compounds has been focused principally on their potent cytotoxic effects, 3 although other antiviral and inhibitory activities on protein phosphatase type 2A have also been reported. 4,5 This type of cytotoxic compounds have been studied in the course of our research into the secondary metabolites of Laurencia species 6–8 and recently we reported the identifi- cation of several new examples such as martiriol 1, dioxepandehydrothyrsiferol 2 and pseudodehydro- thyrsiferol 3, isolated from specimens of Laurencia viridis collected around the Canary Islands. 9 0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S0040-4020(02)00912-2 Tetrahedron 58 (2002) 8119–8125 * Corresponding author. Tel: þ34-922-318586; fax: þ34-922-318571; e-mail: jjfercas@ull.es Keywords: polyethers; terpenoids; squalene; marine metabolites.