Synthesis of Ecteinascidin 743 Analogues from Cyanosafracin B: Isolation of a Kinetically Stable Quinonimine Tautomer of a 5-Hydroxyindole

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.