Phthalimido derivatives of cyanosafracin B have been synthesized as analogues of the antitumor agent ecteinascidin 743. As part of this study, a quinoneimine has been prepared, which is a kinetically stable tautomer of a 5-hydroxyindole. This quinoneimine tautomer is stable under acidic and mild basic conditions.
![Synthesis of Ecteinascidin analogues from Cyanosafracin B: isolation of a kinetically stable quinonimine tautomer of a 5-hydroxyindole](https://www.iciq.org/wp-content/uploads/2014/03/Synthesis-of-Ecteinascidin_eng_noticies_articles_2006_64.gif)