Probing Indole Diketopiperazine-Based Hybrids as Environmental-Induced Products from Aspergillus sp. EGF 15-0-3
Org Lett. 2021 Dec 13. doi: 10.1021/acs.orglett.1c03795. Online ahead of print.
Comprehensive analyses of the metabolite spectra of Aspergillus sp. EGF 15-0-3 under different culture conditions revealed the presence of unique environmental-induced metabolites exclusively from the rice medium. Subsequent target isolation afforded four unprecedented indole diketopiperazine-based hybrids with a pyrano[3′,2′:7,8]isochromeno[4,3-b]pyrazino[2,1-i]indole core (1 and 2) or a spiro[piperazine-2,2′-pyrano[3,4,5-de]chromene] scaffold (3 and 4). Putative biosynthetic pathways for 1–4, with Diels-Alder cycloadditions as key steps, were proposed. 1–4 exhibited selective cytotoxicities among several human cancer cells.