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Polycarpine 1 , a highly cytotoxic marine natural product, has been synthesized in three steps from p-methoxyphenacyl bromide 4 in 57% overall yield. The key reaction for construction of the symmetrically substituted disulfide linkage of polycarpine is the treatment of 2-amino-4-(4-methoxyphenyl)-1-methylimidazole 17 with S2Cl2 in acetic acid. In a similar way ten related compounds, including three thiazole analogues, have been prepared. Most of them exhibit high cytotoxic activities against an array of human cancer cell lines.

Three new sulfur-containing alkaloids, polycarpaurines A ( 1 ), B ( 2 ), and C ( 3 ) were isolated from the tropical ascidian Polycarpa aurata collected in Indonesia, together with six known compounds ( 4 – 9 ). The structures of new compounds were assigned on the basis of their spectral data. Compounds 1 , 3 , 4 , and 8 inhibited colony formation of Chinese hamster V79 cells with EC 50 values of 6.8, 8.6, 3.8, and 10 μM, respectively. Compounds 2 and 7 showed modest activity against V79 cells (EC 50 >10 μM).