Total Syntheses of Xiamycins A, C, F, H and Oridamycin A and Preliminary Evaluation of their Anti-Fungal Properties

Divergent and enantiospecific total syntheses of the indolosesquiterpenoids xiamycins A, C, F, H and oridamycin A have been accomplished. The syntheses, which commence from (R)-carvone, employ a key photoinduced benzannulation sequence to forge the carbazole moiety characteristic of these natural products. Late-stage diversification from a common intermediate enabled the first syntheses of xiamycins C and F, and an unexpected one-pot oxidative decarboxylation, which may prove general, led to xiamycin H. All synthetic intermediates and the natural products were tested for anti-fungal activity. Xiamycin H emerged as an inhibitor of three agriculturally relevant fungal pathogens.