While investigating the cytotoxic activity of the methanol extract of an Australian marine sponge Stelletta sp. (Demospongiae), a new diketopiperazine, cyclo-(4-S-hydroxy-R-proline-R-isoleucine) (1), was isolated together with the known bengamides; A (2), F (3), N (4), Y (5), and bengazoles; Z (6), C(4) (7) and C(6) (8). The isolation and structure elucidation of the diketopiperazine (1), together with the activity of 1-8 against a panel of human and mammalian cell lines are discussed.
Ovenden, S. P. B., Nielson, J. L., Liptrot, C. H., Willis, R. H., Tapiolas, D. M., Wright, A. D., & Motti, C. A. (2011). A new diketopiperazine, cyclo-(4-S-hydroxy-R-proline-R-isoleucine), from an Australian specimen of the sponge Stelletta sp. Marine Drugs, 9(11), 2469–2478. https://doi.org/10.3390/md9112469