Structure, derivatization, and antitumor activity of new griseusins from Nocardiopsis sp.

Four new griseusins, 4'-dehydro-deacetylgriseusin A (1) and 2a,8a-epoxy-epi-deacetylgriseusin B (2) as new constitutional derivatives and epi-deacetylgriseusin A (3) and epi-deacetylgriseusin B (4) as new stereoisomers, were isolated from Nocardiopsis sp. (YIM80133, DSM16644). 4'-Dehydro-deacetylgriseusin A (1) showed pronounced cytotoxic potency (mean IC50 = 0.