Hydrolytic Breakdown of the Euplotins, Highly Strained, Adaptive, Hemiacetal Esters of the Marine Ciliate Euplotes crassus: A Mimic of Degradative Pathways in Nature and a Trick for the Assignment of the Absolute Configuration

Euplotin C((+)‐3), the most abundant of the niche‐exploitation terpenoids of the marine ciliate morphospecies Euplotes crassus, was found to undergo degradation in mildly basic H2O/MeOH by initial hydrolysis of the acetate group, followed by, in turn, hydrolytic ring‐A and ring‐C opening and ring‐A reclosure with indiscriminate C(1)/C(15) methanol trapping to give four diastereoisomeric aldehydic hemiacetals 5–8 in similar proportions; 7, as a model for its congeners, proved biologically inactive. From these, the absolute configuration was assigned via Mosher's ester methodology. These processes may be assumed to mimic inactivation of the euplotins in sea water. Degradation of (+)‐3 in either stronger base or acidic medium was also examined.