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

The complex odor of (R)-ethyl citronellyl oxalate (ECO) was investigated based on its stable conformations. ECO, a flexible chain-type compound, mainly has a musk-like odor, but also has a rose-like odor. The rose-like odor recalls citronellol according to a perfumer's sensory evaluation. The conformational analyses of ECO and (S)-citronellol. were performed using CAChe(TM) (Computer Aided Chemistry) system. Structure optimization of selected conformers was performed with the PM3 method in succession. Twenty-three conformers of ECO were obtained and were compared with the three-dimensional structure model for benzenoid musks previously proposed and also with 22 stable conformers of (S)-citronellol. As a result, we found that the two most stable compact conformers of ECO, which were quite similar, fit the structure model for benzenoid musks, and that a three-dimensional partial structure of another conformer of ECO was similar to one conformer of (S)-citronellol. Thus, the main odor quality of ECO, the musk-like odor, could be explained by the most stable compact conformers. We also showed that the secondary 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 conformer of (S)-citronellol.