Abstract The Bakkenolide group 1 3 of sesquiterpenes present two interesting synthetic problems. The cisdimethyl cis-hydrindane portion 2, because of its structural and stereochemical relationship with the eremophilane sesqui terpenes, 4 has synthetic solutions available. 5 The spiro-β-methylene-γ-butyrolactone unit 3, 6 which is presently unique to this class of natural products, has been synthesised by four different routes. 7–10
