Novel antilipid peroxidative carbazole alkaloids, antiostatin A(5) (1), antiostatin A(6) (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.