Protected aminopentanoic acid derivative (I) is converted into phenylpentanone (II) by first treatment with thionyl chloride in refluxing benzene, followed by condensation with benzene and aluminum chloride. Reduction of (II) with aluminum isopropoxide in refluxing isopropanol provides phenylpentanol derivative (III), which is then treated with hydrazine hydrate in refluxing EtOH to furnish 2-amino-4-methyl-1-phenylpentane-1-ol (IV). Coupling of (IV) with chloro derivative (V) at 110-120 C yields derivative (VI), which is finally converted into the desired oxazolidinone by reaction with ethyl chlorocarbonate (VII) in chloroform followed by heating in toluene and treatment with aluminum isopropoxide.