The reaction of N-(benzyloxycarbonyl)-L-serine methyl ester (I) with Ts-Cl gives the corresponding tosylate (II), which is condensed with 4-phenoxythiophenol (III) to yield the thioether (IV). The oxidation of (IV) with Oxone affords the sulfone (V), which is N-deprotected with H2 over Pd/C to provide compound (VI) with a free amino group. The methylation of (VI) with methyl iodide gives the N-methyl derivative (VII), which is finally treated with hydroxylamine to afford the target hydroxamic acid.