Abstract: Evidence is presented to demonstrate that marasmic acid has the structure 9. A reasonable biosynthetic pathway for the genesis of this compound through a humulene precursor is suggested and supported by the activity of the acetic acid obtained by the Kuhn- Roth oxidation of labeled 9 and of 15, a reduction product of marasmic acid in which a methyl group is generated from the cyclopropane ring. arasmic acid was first reported by ...