Macrocyclic terpenes, such as diterpenic nephthenol 1 and cembrene-A 2, and sesquiterpenic hedycaryol 3, were synthesized by anion-induced cyclization of suitably functionalized acyclic terpenes. Thus, the diterpenic epoxy thioether 6 derived from E, E-geranyllinalool yielded 7 by the action of n-BuLi in the presence of DABCO. Desulfurization of 7 afforded 1 and its isomer 8. Treatment of 1 with SOCl_2 gave 2 which is known to be termite trail pheromone of Nasutitermes sp. Geometry of all double bonds in 1 and 2 were established. Interestingly, 2 has pheromonal activity also to Coptotermes formosanus and Reticulitermes speratus. Cyclization of the E,E-farnesyl derivative 11 on the contrary afforded 12 and 13, while 16 was obtained as the major product from the Z,E-derivative 15 under the same condition. Desulfurization of 12 afforded inseparable mixture of 3 and 17. Thermolysis of the mixture converted 3 to elemol 18, and left 17. Similarly 13 gave 19 which was converted to cis-elemol 20 by Cope rearrangement. Desulfurization of 16 yielded a mixture of 22 and 23. Treatment of 19 with acid afforded 24 and 25. Stereochemistry of these three products from 19 revealed the conformation of 10-membered ring in each transition state.
