STRUCTURE AND SYNTHESIS OF (+/-)-CAUDOXIRENE, A NEW SPERMATOZOID-RELEASING AND SPERMATOZOID-ATTRACTING PHEROMONE FROM THE MARINE BROWN ALGA PERITHALIA-CAUDATA (PHAEOPHYCEAE, SPOROCHNALES) .5.

Cis‐3‐(trans‐1,2‐Epoxybut‐3‐enyl)‐4‐vinylcyclopentene ((±)‐4, caudoxirene) is a new gamete‐releasing and gamete‐attracting pheromone from the marine brown alga Perithalia caudata (Sporochnales). The key step of its synthesis is the diastereoselective alkylation of the aldehyde 8 with the [(phenylthio)allyl]titanium reagent 9 to yield the erythro‐β‐hydroxy sulfide 10 which affords 4 on sequential treatment with Me3O·BF4 and aq. NaOH. The lowest effective concentration of (±)‐4 for gamete‐release is found at 1.4 × 10−11 mol/l seawater. Copyright © 1990 Verlag GmbH & Co. KGaA, Weinheim