Selective hydrolysis of the cladinose moiety of 6-O-methylerythromycin (I) with aqueous HCl gave (II), which was selectively acetylated at 2'-OH to provide acetate (III). Pfitzner-Moffat oxidation with DMSO, EDC, and pyridinum trifluoroacetate yielded 3-oxo compound (IV). Then, reaction with methanesulfonic anhydride in pyridine gave 11-O-mesylate (V), which on treatment with DBU in acetone produced the elimination product (VI). Subsequent condensation with carbonyldiimidazole in the presence of NaH afforded imidazole-carboxylate (VII). Then, reaction with hydrazine in aqueous acetonitrile provided a mixture of epimeric oxazolidinones (VIII) and (IX), which were separated by column chromatography.

Wittig reaction of 4-quinolinecarboxaldehyde (X) with dioxolanylmethyl phosphonium salt (XI) using potassium tert-butoxide in THF produced olefin (XII), which was reduced by catalytic hydrogenation to afford (XIII). Hydrolysis of acetal (XIII) with HCl in acetone-H2O gave quinolinylpropanal (XIV). Finally, reductive alkylation of N-aminoisoxazolone (VIII) with aldehyde (XIV) using NaBH3CN/AcOH in MeOH provided the target compound.