Two pairs of new dimeric diketopiperazine alkaloids, ( ±)-dibrevianamides Q1 and Q2 (( ±)-1 and ( ±)-2), together with seven previously reported analogues (( ±)-3, 4-6, and ( ±)-7) were obtained from a marine-derived fungus Aspergillus sp. The structures of ( ±)-1 and ( ±)-2 were clarified using comprehensive spectroscopic analyses, the calculated ECD, and DP4 + probability methods. Speculated from the biogenesis, ( ±)-dibrevianamides Q1 and Q2 (( ±)-1 and ( ±)-2) might be the key precursor of [2 + 2] diketopiperazine dimers (( ±)-3). Compounds ( +)-1 and ( -)-2 displayed anti-H1N1 virus activity with IC50 values of 12.6 and 19.5 μM. Compound ( +)-1 showed significant activity against Mycobacterium tuberculosis (MIC, 10.2 μg/mL). KEY POINTS: • Two pairs of new dimeric diketopiperazine alkaloids were obtained from the marine-derived fungus Aspergillus sp. • The structures of the new compounds were clarified using comprehensive spectroscopic analyses, the calculated ECD, and DP4 + probability methods. • ( ±)-Dibrevianamides Q1 and Q2 were speculated to be the key precursor of [2 + 2] diketopiperazine dimers ( ±)-asperginulin A.
Keywords: Aspergillus sp.; Bioactivity; DP4 + probability; Dimeric diketopiperazine alkaloid; Electron circular dichroism.
© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.