RELATION BETWEEN THE ODOR OF (R)-ETHYL CITRONELLYL OXALATE AND ITS STABLE CONFORMATIONS

The complex odor of (R)-ethyl citronellyl oxalate (ECO) was investigat ed based on its stable conformations. ECO, a flexible chain-type compo und, mainly has a musk-like odor, but also has a rose-like odor. The r ose-like odor recalls citronellol according to a perfumer's sensory ev aluation. The conformational analyses of ECO and (S)-citronellol. were performed using CAChe(TM) (Computer Aided Chemistry) system. Structur e optimization of selected conformers was performed with the PM3 metho d in succession. Twenty-three conformers of ECO were obtained and were compared with the three-dimensional structure model for benzenoid mus ks previously proposed and also with 22 stable conformers of (S)-citro nellol. As a result, we found that the two most stable compact conform ers of ECO, which were quite similar, fit the structure model for benz enoid musks, and that a three-dimensional partial structure of another conformer of ECO was similar to one conformer of (S)-citronellol. Thu s, the main odor quality of ECO, the musk-like odor, could be explaine d by the most stable compact conformers. We also showed that the secon dary odor quality of ECO, a rose-like odor, was possibly due to one of the stable conformers of ECO that is partially similar to the conform er of (S)-citronellol.