Terpenoids-LXXXIII: structure of β-bergamotene

β-Bergamotene, in Indian valerian root oil, is a sesquiterpene analogue of β-pinene. Its structure has been established as I by application of physical methods and chemical degradations to known compounds, pinane (XXIX) and bicycloekasantalic lactone (XXXIII). The possible biogenesis of β-bergamotene and its relationship to other sesquiterpenes, such as α- and β-santalenes has been discussed and conclusions drawn regarding its stereochemistry by comparison of the NMR spectra of these related products