Synthesis of Methylene-Bridged Biscarbazole Alkaloids by using an Ullmann-type Coupling: First Total Synthesis of Murrastifoline-C and Murrafoline-E.

We describe the total synthesis of methylene-bridged biscarbazole alkaloids by using a late-stage Ullmann-type coupling of fully functionalised carbazole subunits. The carbazole derivatives were synthesised via a sequence of palladium(0)- and palladium(II)-catalysed coupling reactions. Our approach has provided bismurrayafoline-A, bismurrayafolinol, chrestifolines B-D, and the first total synthesis of murrastifoline-C and murrafoline-E.