Synthesis and initial biological evaluation of myxocoumarin B

The myxocoumarins A and B from Stigmatella aurantiaca MYX-030 are natural products featuring unusual nitro-and long-chain alkyl substitution. While myxocoumarin A was shown to exhibit strong antifungal properties, the antifungal potential of myxocoumarin B was not yet assessed due to low production titers during initial isolation. We therefore developed a total synthesis of myxocoumarin B that involves a late-stage Pd-catalyzed nitration of the coumarin core. The availability of synthetic material facilitated the initial evaluation of the bioactivity of myxocoumarin B, which revealed a lack of activity against medically relevant Candida sp. and low cytotoxicity in vitro against human fibroblasts (MRC-5) and in vivo (zebrafish).