We have previously reported a synthesis of ene-hydrazide from enol triﬂate and a subsequent indolization reaction as a new entry to the regioselective Fischer indole synthesis.1 In this process, a base-catalyzed intramolecular aza-Michael reaction, in situ trapping of the resulting enolate, and subsequent C-N coupling with phenyl hydrazide afforded the key ene-hydrazides. This new synthetic strategy has been successfully applied to the total synthesis of (+)-aspidospermidine and (-)-tabersonine.2
Toward further development of our strategy, we have envisaged a new synthetic route to (-)-tubifolidine and uleine. With carbamate 1 and 5, the carbamic anion mediated Michael addition followed by triflation will give bicyclic compound 2 and 6. Buchwald-Hartwig type amination and regioselective Fischer indolization under Lewis acidic conditions would selectively afford desired indole 4 and 8. Presented herein are the progress toward the syntheses of (-)-tubifolidine and uleine.