A plenty of cytochrome P450s have been annotated in the Daldinia eschosholzii genome. Inspired by the fact that some P450s have been reported to catalyze the carbon-nitrogen (C-N) bond formation, we were curious about whether hybrids through C-N bond formation could be generated in the indole-3-carbinol (I3C) exposed culture of D. eschscholzii. As expected, two skeletally undescribed polyketide-indole hybrids, designated as indolpolyketone A and B (1 and 2), were isolated and assigned to be constructed through C-N bond formation. Their structures were elucidated by 1D and 2D NMR spectra. The absolute configurations of 1 and 2 were determined by comparing the recorded and calculated electronic circular dichroism (ECD) spectra. Furthermore, the plausible biosynthetic pathways for 1 and 2 were proposed. Compounds 1 and 2 exhibited significant antiviral activity against H1N1 with IC50 values of 45.2 and 31.4 μM, respectively. In brief, compounds 1 and 2 were reported here for the first time and were the first example of polyketide-indole hybrids pieced together through C-N bond formation in the I3C-exposed culture of D. eschscholzii. Therefore, this study expands the knowledge about the chemical production of D. eschscholzii through precursor-directed biosynthesis (PDB).
Keywords: C–N bond formation; Daldinia eschosholzii; Indole-3-carbinol; P450; Polyketide-indole hybrids; Precursor-directed biosynthesis.
© 2022 The Authors.