A method of forming a macrocyclic musk compound comprising the steps of:— i) cross-metathesizing a first olefin and a second olefin in the presence of a homogeneous transition metal catalyst comprising an alkylidene ligand, to form a statistical mixture of a hetero-dimer intermediate of said first and second terminal olefin, and homo-dimers ii) separating the hetero-dimer from the statistical mixture of hetero- and homo-dimers iii) and cyclizing the hetero-dimer intermediate to form the macrocyclic musk compound.