Cyclosantalal and epicyclosantalal—new sesquiterpene aldehydes from east Indian sandalwood oil

Two new minor components of East Indian sandalwood oil have been isolated by chromatography. Structure elucidation using spectroscopical methods resulted in formulae 1 and 2. The relative configurations of the epimeric sesquiterpene aldehydes 1, 2 were determined by two‐dimensional NMR‐analysis (HETCOR‐, INADEQUATE‐, and NOE‐experiments) of the corresponding acids, cyclosantalic acid (3) and epicyclosantalic acid (4). The proposed structures of the aldehydes were confirmed by oxidative degradation reactions. Both aldehydes could be oxidized under normal conditions resulting in the known products acetyldihydroalbene (7) and albene (12) but also some new products such as the acids 3,4 and the formates 8,9. Trace amounts of those oxidation products could also be detected as constituents of sandalwood oil. A possible biogenetic pathway leading from p‐santalane derivatives to the cyclosantalals is briefly discussed.