A compound of formula (I) wherein R1 and R2 are independently selected from hydrogen, methyl, ethyl, propyl and isopropyl or R1 and R2 together form a saturated or monounsaturated 5- or 6-membered hydrocarbon ring, as represented by the arcuate dotted line R3 is selected from methyl and ethyl R4 is selected from methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, cyclobutyl and cyclopentyl R5 is selected from hydrogen and methyl, and the dotted line between positions 3&Prime and 4&Prime represents an optional double bond. The compounds have a musk odour and are useful in fine and functional fragrances.
