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Dalesindole, an antibacterial and anti-inflammatory indole alkaloid with an undescribed carbon skeleton, was stereoselectively constructed by Daldinia eschscholzii through class II aldolase catalyzed Michael addition of fungal chromone with 3,3'-diindolylmethane (DIM) formed in situ from indole-3-carbinol (I3C) under catalyses of monooxygenase and 8-amino-7-oxononanoate synthase (AONS). Dalesindole isomerizes via a retro-Michael reaction to give stereoisomers with bioactivities. The work provides an access to new bioactive hybrids of fungal oligoketide with microbially decorated exogenous chemistry.

The conversion from triene- to diene-typed ansamycins is clarified step by step in Streptomyces seoulensis IFB-A01. Such an intertype convertibility is adopted to establish for the first time the simultaneous mutasynthesis of both types of C17-benzene ansamycins (C17BAs). Three of the newly generated unnatural compounds showed potent cytotoxicity.

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