Thesis (M.Sc. in Pharm.)--Chulalongkorn University, 2000

A Thai Ecteinascidia tunicate, collected from Phuket, was investigated for its chemical constituents. By treatment the tunicate sample with potassium cyanide, two cyano-derivatives of tris-tetrahydroisoquinolines, ecteinascidin 770 (ET 770) and the new compound ecteinascidin 786 (ET 786), were isolated together with a pyrimidine nucleoside, thymidine. The complete carbon-NMR assignments of ET 770 were reported herein. The cyano-derivative ET 770 was converted into the natural-occurring hydroxide derivative ET 743 by treatment with AgNO[subscript 3]. The chemical structures and relative stereochemistry of these compounds were elucidated through extensive analyses of their MS, UV, IR, and NMR spectroscopy, as well as comparison with the previously reported data. The compounds ET 770 and ET 786 showed strong cytotoxicity against human epidermoid carcinoma cells of the nasopharynx and breast cancer cells.