Morindolestatin, Naturally Occurring Dehydromorpholinocarbazole Alkaloid from Soil-Derived Bacterium of the Genus Streptomyces.

Novel antilipid peroxidative carbazole alkaloids, antiostatin A5 (1), antiostatin A6 (2), and (±)-morindolestatin (3), were isolated from a new soil-derived Streptomyces sp. Compound 2 possesses an unusual cyclohexene side chain. Compound 3 was a pair of enantiomers featuring an unprecedented [1,4]oxazino[2,3-c]carbazole ring system. The absolute configuration of 3 was determined by online HPLC-ECD and ECD calculation. A racemization mechanism and putative biosynthetic pathway are discussed.