Biomimetic Total Syntheses of Dixiamycins A, B, and C via Riboflavin-Catalyzed Oxidative C-N and N-N Bond Formations.

Flavin-mediated biomimetic photoredox catalysis remains largely underexplored in the synthesis of complex natural products. Herein, we report a biomimetic flavin-mediated photoredox radical dimerization strategy for the total synthesis of dixiamycins A (1a), B (1b), and C (1c). This approach proceeds via in situ generation of a N-centered radical from xiamycin A methyl ester TMS ether (2c). The N radical is stabilized through conjugation and undergoes delocalization to form a C radical at the para position relative to nitrogen. Subsequent selective radical coupling enables both N-N homocoupling and C-N heterocoupling pathways, ultimately affording the three major naturally occurring dixiamycins (1a-1c).