Compound (I) as a 2:1 mixture of diastereoisomers was hydrolyzed with barium hydroxide to afford a mixture of alcohols (II). Further reaction with thiocarbonyldiimidazole (III) and dimethylamino-pyridine (DMAP) gave thiocarbamate (IV), which was finally reduced with tributyltin hydride and azabis(isobutyronitrile) (AIBN) in refluxing benzene.
Treatment of quinoline (I) with ethynylmagnesium bromide (II) in THF at low temperature, and then with 4-chlorophenyl chloroformate (III) gave carbamate (IV). Subsequent deprotection of tert-butyldimethylsilyl group with p-toluenesulfonic acid yielded allyl alcohol (V), and this was stereoselectively epoxidized with m-chloroperbenzoic acid to give epoxyalcohol (VI). Coupling of (VI) with vinyl chloride (VII) in the presence of Pd(0)-CuI catalyst provided the enediyne compound (VIII). This was oxidized with Dess-Martin periodinane reagent to the aldehyde (IX). Finally, CsF-promoted cyclization in the presence of acetic anhydride provided the title compound as a 2:1 mixture of diastereoisomers, which could not be separated.