Syntheses totales et etudes de lignanes biologiquement actifs--III

Kinetically controlled intramolecular α-hydroxyalkylation of a suitable diphenyl aldehyde lactone gave a dibenzocyclooctenolactone having a cis lactone-ring junction, such as (±)-picrostegane and (±)-isopicrostegane. Subsequent transformations led to the known (±)-isostegane. The chemical properties, the physical data and biological activity of these three diastereoisomers were compared with those of(±)-stegane, a fourth diastereoisomer obtained by hydrogenolysis of synthetic (±)-steganacin.