Synthesis of xestomanzamines A and B

Synthetic pathways are described for the synthesis of two naturally occurri ng beta -carbolines, xestomanzamine A and B. The synthesis of aromatic xest omanzamine A was most conveniently achieved by way of a Grignard reaction i n dichloromethane. This route is suitable for the synthesis of analogues wi th modifications in the imidazole ring of xestomanzamine A. Xestomanzamine B, an oxidation-sensitive dihydro-beta -carboline, was prepared by Pictet-S pengler condensation of tryptamine with a vicinal tricarbonyl substituted i midazole.