Total Synthesis and Biological Activity of Marine Alkaloid Eudistomins Y(1)–Y(7) and Their Analogues

Eudistomin Y class compounds are a series of β-carbolines which was originally isolated from a marine turnicate or ascidian near the South Korea Sea. These compounds contain bromo-substituted groups, which is one of the typical characters of marine natural products. We report herein the chemical synthesis and biological evaluation of seven new β-carboline-based metabolites, Eudistomins Y(1)–Y(7), and their hydroxyl-methylated phenyl derivatives. Using bromo-substituted tryptamines and bromo-substituted phenylglyoxals as the key intermediates, Eudistomins Y(1)–Y(7) and their derivatives were synthesized via the acid-catalyzed Pictet-Spengler reaction and fully characterized by (1)H- and (13)C-NMR and mass spectroscopy. Biological studies revealed that all of the compounds showed moderate growth inhibitory activity against breast carcinoma cell line MDA-231 with IC(50) of 15–63 μM and the inhibitory activities of hydroxyl-methylated phenyl products were higher than that of the corresponding natural products Eudistomins Y(1)–Y(7).