The structures of cytochalasins A and B

The structures of cytochalasins A and B, metabolites of Helminthosporium dematioideum showing novel effects on mammalian cells, have been determined. Cytochalasin B is identical with phomin. (–)-α-Methyladipic acid is shown to have the R-configuration contrary to a previous assignment; the absolute configurations of the Nupheus alkaloids therefore require revision.