The molecule is the steroid acid anion formed by loss of a proton from the carboxy group of helvolic acid; major microspecies at pH 7.3. It is a conjugate base of a helvolic acid.
(2Z)-2-[(4S,5S,6S,8S,9S,10R,13R,14S,16S)-6,16-diacetyloxy-4,8,10,14-tetramethyl-3,7-dioxo-5,6,9,11,12,13,15,16-octahydro-4H-cyclopenta[a]phenanthren-17-ylidene]-6-methylhept-5-enoate