New norditerpenoids and a diterpenoid from a sponge that inhibit the lyase activity of DNA polymerase β

Using an assay to detect inhibitors of the lyase activity of DNA polymerase β, bioassay-directed fractionation of a CHCl3 extract of an unidentified sponge of the family Demospongiae resulted in the isolation of the new diterpenoid , the new bis-norditerpenoids , and the two known compounds spongia-13(16),14-dien-19-oic acid (), and methylspongia-13(16),14-dien-19-oate (). The structures of the new compounds were established on the basis of extensive 1D and 2D NMR spectroscopic interpretation. All five compounds inhibited the lyase activity of DNA polymerase β.