Synthesis of sesquiterpenoids of biogenetic importance

The contribuation made by Sir Robert Robinson to sesquiterpene chemistry and to the development of the biogenetic isoprene rule are discussed. Examaples of the great utility of the Robinson Ring Annelation in synthetic organic chemistry are given with reference to steroid and sesquiterpene systems. Recent modifications to the original method are also mentioned. The close relationship of the eremophilane sesquiterpenes and the spiro sesquiterpenes, which follows from the biogenetic derivation of eremophilone by Robinson, is the basis for the synthetic strategy under discussion leading to chiral spiro sesquiterpenes. This approach makes use of chiral starting material couples with subsequent stereospecific processes leading to sesquiterpenes of stereochemical interest and complexity.