Kamil Lisiecki, Krzysztof K. Krawczyk, Piotr Roszkowski, Jan K. Maurin, Armand Budzianowski, Zbigniew Czarnocki
Lignan, Podophyllotoxin, Photochemistry, Visible-light photolysis, Amide cleavage
During the attempted photochemical,cyclization of 2,3-bisbenzylidene-y-hydroxybutyric acid cyclic amide ester, it was observed that a gamma-butyrolactone ring was formed, which was concurrent with the release of the amine fragment from the amide. The process occurs with high yield giving rise to the formation of beta-apopicropodophyllin and its regioisomer. Additional experiments confirmed the photochemical nature of this transformation, and that it is independent from the photocyclization of the benzylidene groups a typical reactivity for the members of the fulgide family. In contrast to the latter UV-driven cyclization, the photochemical cleavage of the amide was proven to proceed under irradiation with visible light.