Acetylation of leucomycin A7 at 2' hydroxyl group with Ac2O in acetonitrile yielded acetate (II), which was then protected with tert-butyldimethylsilyl chloride in the presence of imidazole in DMF to provide the silyl cyclic acetal (III). Two-phase basic hydrolysis under controlled conditions removed chemoselectively the 4'' propionyl ester to give alcohol (IV), and further esterification with n-butyryl chloride in pyridine afforded butyrate (V).

To introduce the 3''-O-methyl group, compound (V) was first converted to methylthiomethyl ether (VI) on treatment with dimethyl sulfoxide and benzoic anhydride at 45 C, followed by methanolysis of the 2'-acetyl ester to give (VII). Then, a hydrogenolytic cleavage of the thioether group with Raney Nickel furnished the 3''-O-methyl compound (VIII). Finally, removal of the two TBDMS groups with 2 M tetrabutylammonium fluoride in THF yielded the target compound.