Abstract
4′-Demethylepipodophyllotoxin (4′-DMEP) was readily available through demethylation of podophyllotoxin using methionine in methanesulfonic acid in the presence of TFA (or acetone/water). Thus, 4-amino-4-deoxy-4′-demethylepipodophyllotoxin was obtained in three steps in excellent yield by a Ritter reaction on 4′-DMEP, followed by treatment with thiourea in AcOH.
GRAPHICAL ABSTRACT
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ACKNOWLEDGMENTS
We thank Daniel Dauzonne and Claude Monneret from Institut Curie (Paris) for their interest and exploitation of the demethylation procedure.
Notes
a Presence of 2% of 4c (4-epimer of starting material).
b Presence of di- and tri-demethylated compounds 5a (1%) and 5b (0.5%).
c Presence of di-demethylated compound 5a (0.5%).
d In the absence of acetone/water.