Five new diketopiperazine derivatives, (3Z,6E)-1-N-methyl-3-benzy lidene-6-(2S-methyl-3-hydroxypropylidene)piperazine-2,5-dione (1), (3Z,6E)-1-N-methyl-3-benzylidene-6-(2R-methyl-3-hydroxypropylidene)piperazine-2,5-dione (2), (3Z,6Z)-3(4-hydroxybenzylidene)-6-isobutylidenepiperazine-2,5-dione (3), (3Z,6Z)-3-((1H-imidazol5-yl)-methylene)-6-isobutylidenepiperazine-2,5-dione (4), and (3Z,6S)-3-benzylidene-6(2S-but-2-yl)piperazine-2,5-dione (5), were isolated from the marine-derived actinomycete Streptomyces sp. FXJ7.328. The structures of 1-5 were determined by spectroscopic analysis, CD exciton chirality, the modified Mosher's, Marfey's and the C-3 Marfey's methods. Compound 3 showed modest antivirus activity against influenza A (H1N1) virus with an IC50 value of 41.5 +/- 4.5 mu M. In addition, compound 6 and 7 displayed potent anti-H1N1 activity with IC50 value of 28.9 +/- 2.2 and 6.8 +/- 1.5 mu M, respectively. Due to the lack of corresponding data in the literature, the C-13 NMR data of (3Z,6S)-3-benzylidene-6-isobutylpiperazine-2,5-dione (6) were also reported here for the first time.

Streptomyces; diketopiperazine derivatives; antivirus activity; H1N1

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