Ring contraction of the 16-membered lactone skeleton of josamycin (I) to the 14-membered lactone (III) is accomplished by olefin metathesis in the presence of Nolan catalyst (II) and 1-hexene. Subsequent deacetylation of (III) employing K2CO3 in MeOH gives rise to the title compound.
In a closely related procedure, leucomycin A1 (I) is subjected to olefin metathesis in the presence of Nolan catalyst (II) and 1-hexene to furnish the title compound.