Prenylated indole diketopiperazine alkaloids as phosphatase inhibitors from the marine-derived fungus Talaromyces purpureogenus

Six previously undescribed prenylated indole diketopiperazine alkaloids, talaromyines A-F (1−6), were isolated from the marine-derived fungus Talaromyces purpureogenus SCSIO 41517. Their structures including absolute configurations were elucidated on the basis of comprehensive spectroscopic data including NMR, HR-ESI-MS, and electronic circular dichroism calculations, together with chemical analysis of hydrolysates. Compounds 1−5 represent the first example of spirocyclic indole diketopiperazines biosynthesized from the condensation of L-tryptophan and L-alanine. Compounds 2 and 4−5 showed selective inhibitory activities against phosphatases TCPTP and MEG2 with IC50 value of 17.9−29.7 μM, respectively. Compounds 4−5 exhibited mild cytotoxic activities against two human cancer cell lines H1975 and HepG-2.