Racemic cyclosativene has been prepared stereospecifically by two routes each involving intramolecular capture of a homoallylic carbonium ion by a carbon-carbon multiple bond. Diels-Alder reaction between propynal and 2,3-dimethylcyclopentadiene followed by suitable elaboration of the product 15 gave the requisite norbornenyl tosylates 23 and 39 possessing endo-substituted alkene and alkyne side chains, respectively. Solvolysis of each in trifluoroethanol afforded tetracyclic products! 25 and 40, contaminated with tricyclic material in the case of 23, demonstrating the superiority of the alkyne group in achieving complete cyclization. The conversions of 25 and 40 to cyclosativene were effected in five and six steps, respectively. © 1980, American Chemical Society. All rights reserved.