Some Aspects of the Molecular Surface of Sandalwood Odour Molecules. Conformational Calculations on Sandalwood Odour VII [1]

The examination of molecular surfaces seems to be a very promising tool for the investigation of sandalwood odour molecules [1-4]. These com­ pounds usually contain terpenoid structures with a polar group, often a hydroxyl group, and a rather hydrophobic voluminous residue at the other side of the molecule. It has been shown that the shape of the molecules mainly determines the biological effect, the fragrance, in a quite sensitive manner. Small structural changes lead to a complete disap­ pearance of the sandalwood odour [5], For some substances it has also been proven that only one chiral enantiomeric form is odoriferous [6, 7]. For the present study the molecular surfaces of some sandalwood odour molecules were compared us­ ing a method described before [3] and the shape of a part of the molecular surfaces, which might be of importance for an association at a receptor site, was evaluated. The ‘mean’ molecular surface: Five different odour molecules were used to find parts of the molecular surfaces which are common for all of them, despite their rather different struc­ ture: /-Butylbicyclodecanol (I) [8], exo-isocamphanylcyclohexan-(3)-ol (II a and II b) [9], trimethyl-cyclopentenyl-cyclohexan-(3)-ol (III) [10] and /?-santalol (IV) (see picture 1). These molecules are described to possess typical sandalwood odour. They are either of natural origin (IV) or synthetic products.