(±)-3-oxovincadifformine ethyl ester 14 has been synthesized through an intramolecular [4π+ 2π] cycloaddition of the 3-oxosecodine 13 first prepared in turn from the enamide 10 by dehydrogenation with benzeneseleninic anhydride. An insight into the conversion of 10 into 13 was gained, resulting in the suggestion of a plausible mechanistic pathway.
