A compound of formula (I) wherein R1 and R2 are independently selected from hydrogen, methyl, ethyl, propyl and isopropyl; or R and R 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" and 4" represents an optional double bond. The compounds have a musk odour and are useful in fine and functional fragrances.