Eudistomidins H–K, new β-carboline alkaloids from the Okinawan marine tunicate Eudistoma glaucus

Four new β-carboline alkaloids, eudistomidins H–K (1–4), were isolated from an Okinawan marine tunicate Eudistoma glaucus and the structures of 1–4 were elucidated on the basis of spectroscopic data. Eudistomidins H (1) and I (2) were new β-carboline alkaloids possessing a unique fused-tetracyclic ring system consisting of a tetrahydro β-carboline ring and a hexahydropyrimidine ring. Eudistomidin J (3) showed relatively potent cytotoxicity against murine leukemia cells P388 and L1210, and human epidermoid carcinoma cells KB in vitro.

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