Total synthesis of aspidostomide G from a brominated tryptamine

Abstract

The first total synthesis of aspidostomide G using a brominated tryptamine is described. The synthetic route features several notable aspects: (a) the starting material, compound 13, contains a built-in hydroxy group and was transformed to the Sonogashira reaction precursor; (b) the construction of the indole ring was achieved through a transition-metal catalyzed synthesis and a 5-endo-dig cyclization. The desired indole 9 was synthesized in only 7 steps with an overall yield of 54% and required only three columns; (c) a late C2-bromination was achieved by using the 4-acetoxyindole analogue 14c.