A compound of general formula (I) with or without the double bond illustrated by the dotted line. In formula (I), X is a CHO, CH2OH, CH2OC(O)R or CH(OR)2 group, and R represents a linear or branched C1-C5 alkyl or alkenyl chain. The synthesis method for the compound, and especially the 6,8-dimethyl-non-7-enal (1) prepared by the hydroformylation of the 5,7-dimethyl-octa-1,6-diene is also disclosed, as well as compositions containing the compounds of formula (I). Due to the odorant properties the...