(±)-Dibrevianamides Q1 and Q2, the key precursors of asperginulin A from a marine-derived fungus

Abstract

Abstract: 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. Graphical abstract: [Figure not available: see fulltext.].