Condensation of 1,2-cyclo-propanedicarboxylic anhydride (I) with chlorobenzylhydrazine derivative (II) in EtOH (1) or acetonitrile affords derivative (III), which then reacts with epoxy-benzopyrancarbonitrile derivative (IV) in the presence of pyridine in EtOH to yield a mixture of two diastereomers (Va-b), from which the desired product is chromatographically separated.