Cytotoxic dinorditerpenoids from Drypetes perreticulata.

Four hitherto unknown dinorditerpenoids, dryperreins A-D of the pimarane class, together with eight known triterpenoids, were isolated from twigs and leaves of Drypetes perreticulata. The structures of dryperreins A-D were elucidated on the basis of detailed spectroscopic analysis as (10S)-11,12-dihydroxy-6-methoxy-15,16-dinorpimara-5,8,11,13-tetraene-3,7-dione, (10S)-6,11,12-trihydroxy-15,16-dinorpimara-5,8,11,13-tetraene-3,7-dione, (10S)-11,12-dihydroxy-6-methoxy-15,16-dinorpimara-1,5,8,11,13-pentaene-3,7-dione, and (10S)-6,11,12-trihydroxy-15,16-dinorpimara-1,5,8,11,13-pentaene-3,7-dione, respectively. Dryperreins C and D exhibited strong cytotoxicity in vitro against HL-60 human tumor cell line. The structure-activity relationship of the cytotoxic compounds was briefly discussed.