Iminophosphorane-mediated synthesis of 1-acyl-beta-carbolines: A new access to the alkaloids eudistomin T, S and xestomanzamine A of marine origin

New syntheses of the alkaloids eudistomin T and S are described. The key step, formation of the 1-phenylacetyl beta-carboline, involves a tandem aza Witrig I electrocyclic ring closure process. The first synthesis of the alkaloid xestomanzamine A is achieved by coupling of a N-protected harmane, now available via aza Wittig / electrocyclic ring closure process, with a 5-lithioimidazole derivative. Copyright (C) 1996 Elsevier Science Ltd