16a,21-trimethyl--stereoisomer

verrucarin A from myrothecium sp

n-17(18h),2’-oxirane)-3,9,14-trione,4,5,6,7,16,16a,19a,22-octahydro-4-hydroxy

spiro(16,18-methano-1h,3h,23h-(1,6,12)trioxacyclooctadecino(3,4-d)(1)benzopyra