Precise structural elucidation of dehydroaltenusin, a specific inhibitor of mammalian DNA polymerase alpha

The X-ray crystal structure of dehydroaltenusin, a specific inhibitor of mammalian DNA polymerase alpha, has previously been reported. We show that dehydroaltenusin exists in an equilibrium mixture of two tautomers possessing gamma-lactone or delta-lactone in polar solvents by NMR experiments. Acetylation of dehydroaltenusin afforded two types of diacetates and two types of monoacetate, possessing gamma-lactone or delta-lactone, respectively. The inhibitory activities of these acetate derivatives against DNA polymerase alpha were all much weaker than that of dehydroaltenusin.