Natural products continue to play a significant role in drug discovery and be a major source for novel pharmaceutical drugs. The fungal natural product daldiquinone (1), which possesses a highly oxidized binaphthyl skeleton, was isolated in 2018 from Daldinia concéntrica, and shown to have antiangiogenesis activity against HUVECs with an IC50 value of 7.5 mM. Another fungal natural product, bulgarein (2), was first isolated in 1976 from the fungus Bulgaria inquinans, and was shown to induce topoisomerase I-mediated DNA cleavage. However, as in the case of daldiquinone (1), total synthesis of bulgarein (2) has yet to be reported. In this work, we report the first total syntheses of daldiquinone (1) and bulgarein (2) starting from the commercially available 1,8-naphthalenediol via a concise route. Among the key steps of these syntheses are selective Suzuki-Miyaura couplings, a Pd-catalyzed C-H arylation and selective oxidation reactions mediated by hypervalent-iodine reagents.

Total syntheses of the fungal natural products Daldiquinone and Bulgarein

ACS Spring Meeting 2021

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