In connection with structure-activity relationship studies, analogues of campholenal ((+)-4b), an important building block for sandalwood-like odorants, were prepared. The five-membered-ring analogues 4 were obtained by epoxidation of the corresponding a -pinene derivatives 2, followed by catalytic ZnBr, isomerisation (Scheme 2). The six-membered-ring skeleton was obtained by ozonolysis of a -campholenyl acetate ((-)-14b), followed by intramolecular aldol condensation (Scheme 5 ) . I3C-NMR assignments are given.