Rearrangement of leinamycin (I) to thioester (III) was achieved by treatment with 4-chloromethyl-5-methyl-2-oxo-1,3-dioxolene (II) in the presence of KI and K2CO3. The required tetrahydropyranyl ether was then obtained by condensation of (III) with dihydropyran (IV) employing camphorsulfonic acid as the catalyst.