Total Syntheses of the Linearly‐Fused Prenylated Indole Alkaloids Asperversiamides H and M via Oxidative Rearrangement of the Putative Biosynthetic Precursor Dihydrocarneamide A

An improved synthesis of the alkaloid dihydrocarneamide A is reported and this has been subjected to a biomimetic‐type oxidative rearrangement using an oxaziridine and so affording the oxidole‐containing and prenylated indole alkaloids (PIAs) asperversiamides H and M. This work serves to confirm the structure assigned to the latter. Oxidation of dihydrocarneamide A using m‐chloroperbenzoic (m‐CPBA) affords an oxidative fragmentation product representing the linear isomer of the PIA amoenamide A and thus a potential “natural product in‐waiting”. Furthermore, oxaziridine‐mediated oxidation of the epimer of dihydrocarneamide A (and the enantiomer of the structure assigned to the natural product asperversiamide F) afforded a mixture of two hitherto unreported oxindoles. Given the manner in which these last two products have been formed it seems likely that these, too, are “natural products in‐waiting”. Certain cytotoxic and antimicrobial properties of key compounds are reported.