(S)-3,7-Dimethyl-5-octene-1,7-diol and Related Oxygenated Monoterpenoids from Petals of Rosa damascena Mill

The methanolic extract obtained from rose flowers was subjected to XAD-2 adsorption chromatography. Prefractionation of the methanolic eluate using multilayer coil countercurrent chromatography (MLCCC) yielded five subfractions. From the least polar subfraction V, a major amount of the key odorants of rose oil, that is, isomeric rose oxides 1a/b, was liberated upon heat treatment at pH 2.5. Further chromatographic workup of fraction V led, for the first time, to the identification of the genuine rose oxide precursor (S)-3,7-dimethyl-5-octene-1,7-diol (2). In addition to diol 2, the following monoterpene diols have been identified: 3,7-dimethyl-7-octene-1,6-diol (3), 2,6-dimethyl-1,7-octadiene-3,6-diol (4), (2E,5E)-3,7-dimethyl-2,5-octadiene-1,7-diol (5), (2E)-3,7-dimethyl-2,7-octadiene-1,6-diol (6), (2Z,5E)-3,7-dimethyl-2,5-octadiene-1,7-diol (7), (2Z)-3,7-dimethyl-2,7-octadiene-1,6-diol (8), (Z)-2,6-dimethyl-2-octene-1,8-diol (9), (E)-2,6-dimethyl-2-octene-1,8-diol (10), (Z)-2,6-dimethyl-2,7-octadiene-1,6-diol (11), (E)-2,6-dimethyl-2,7-octadiene-1,6-diol (12), (2E,6E)-2,6-dimethyl-2,6-octadiene-1,8-diol (13), (2E,6Z)-2,6-dimethyl-2,6-octadiene-1,8-diol (14), 2,6-dimethyloctane-1,8-diol (15), 2,6-dimethyl-7-octene-1,6-diol (16), (E)-3,7-dimethyl-2-octene-1,8-diol (17), (Z)-3,7-dimethyl-2-octene-1,8-diol (18), 3,7-dimethyloctane-1,7-diol (19), 2,6-dimethyl-7-octene-2,6-diol (20), 3,7-dimethyl-6-octene-1,3-diol (21) and (2E)-3,7-dimethyl-2,6-octadiene-1,4-diol (22). Keywords: (S)-3,7-Dimethyl-5-octene-1,7-diol; monoterpene diols; rose oxides; aroma precursors; multilayer coil countercurrent chromatography; rose petals; Rosa damascena Mill.