Carbon-13 spectra of polycyclic systems Tricyclo[3.2.1.02,7]octanes as models for some tetracyclic sesquiterpenes and pentacyclic diterpenes. Ishwarane and trachylobane derivatives

The ¹³C spectra of tricyclo3.2.1.0^2,7]octane, its 1,5-dimethyl derivative and ten tricyclo3.2.1.0^2,7]octan-6-ones have been recorded as model compounds to aid the interpretation of the spectra of the naturally occurring polycyclic terpenes, ishwarane, ishwarone, ishwarol and methyl trachylobanate. The assignments for specific carbons in this series are based on the internal consistency of the observed shielding trends together with the effects of shift reagent on the shieldings of some of these derivatives.