The molecule is an enolate anion resulting from the deprotonation of the enol group of andrastin E. Major species at pH 7.3. Published in http://dx.doi.org/10.1016/j.tet.2013.07.029 It is a conjugate base of an andrastin E.
(3R,5S,8S,9S,10R,13R,14R)-3-hydroxy-14-methoxycarbonyl-4,4,8,10,12,13,16-heptamethyl-15-oxo-2,3,5,6,7,9-hexahydro-1H-cyclopenta[a]phenanthren-17-olate