Divergent Syntheses of Carbazole Alkaloids Clausenapin, Indizoline, Claulansine M, and Clausenaline D.

We described the first total syntheses of clausenapin, indizoline, claulansine M, and a novel synthetic route to clausenaline D via divergent method. Key steps involved TFAA-mediated intramolecular acylation to construct the carbazole core and subsequent Claisen rearrangement to generate key intermediates for further elaboration to target molecules.