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�� and 4�� represents an optional double bond. The compounds have a musk odour and are useful in fine and functional fragrances.
