Aliphatic compounds as fragrants with musk characteristics

A compound of formula I

• wherein
• R1 and R3 are independently hydrogen, methyl, or ethyl;
• R2 is hydrogen, methyl, ethyl, methylene, or ethylidene;
• R4 is C1 to C4 alkyl;
• or
• R4 is vinyl or a linear, branched or cyclic C3 to C4 alkenyl;
• X is carbonyl or a divalent radical —(CMe2)-;
• Y is oxygen or a divalent radical —(CH2)—;
• the bond between C-2 and R2 is a single bond, and the bond between C-2 and C-3 together with the dotted line represents a double bond;
• or
• the bond between C-2 and C-3 is a single bond, and the bond between C-2 and R2 together with the dotted line represents a double bond;
• or
• the bond between C-2 and R2 is a single bond and the bond between C-2 and C-3 is a single bond.