A Convenient New Route to 4-Substituted Benzo[de][3,6]Phenanthrolin-6(6H)-Ones: Important Intermediates in the Synthesis of Ring-A Analogues of the Cytotoxic Marine Alkaloid Ascididemin

Abstract

4-ethylthio- and 4-(4″-methylphenylthio)benzo[de][3,6]phenanthrolin-6(6H)-one have been synthesised in 4 steps from benzoquinone and then readily converted to the 4-amino (6d) and 4-methoxy (6c) analogues by nucleophilic substitution. Further elaboration of 6d leads to the synthesis of 11-hydroxyascididemin, which we have found to exhibit antiviral activity in vitro.