Bioactive Alkaloids from Indole‐3‐carbinol Exposed Culture of Daldiniaeschscholzii

Two new and rare bioactive indoles named dalesindoloids A (1) and B (3), along with 3‐(1H‐indole‐3ylmethyl)‐2‐oxindole (2), were characterized from the indole‐3‐carbinol (I3C)‐exposed culture of Daldinia eschscholzii. The absolute configuration of 2 was determined by quantum chemical calculations of the electronic circular dichroism (ECD) spectrum. Dalesindoloids A and B were cytotoxic against the leukemia HL‐60 cell line with the IC50 values of 1.0 and 7.4 μmol/L, respectively, with the former being inhibitory on Staphylococcus aureus (MIC: 9.1 μmol/L). The simultaneous characterization of the alkaloids from the I3C‐exposed fungal culture highlighted that the 2,3‐epoxyindoline motif can be transformed into both lactam and indolin‐3‐one moieties. This is the first‐time description of the 2,3‐epoxyindoline chemical versatility and Wagner‐Meerwein rearrangement (WMR) reaction in the microbial culture.