New antimalarial dimeric diketopiperazines, piperasagamines A and B, produced by a deep-sea-derived fungus...

Two new dimeric diketopiperazines, piperasagamines A (1) and B (2), were discovered from the cultured material of a deep-sea-derived Aspergillus sp. FKJ-0404 strain. The planar structures of 1 and 2 were elucidated by spectroscopic analysis as dimeric diketopiperazines featuring an α, β-dehydroproline moiety. The absolute configurations of 1 and 2 were determined by advanced Marfey's analysis combined with the analysis of their reduced derivatives. Among them, 2 showed moderate antimalarial activity with an IC₅₀ value of 9.9 µg ml^-1 against Plasmodium falciparum FCR3 strain.