When I visited Purdue University last Fall, Prof. Mingjie Dai shared with me some innovative and highly divergent synthesis of alkaloids that was inspired by their possible biosynthesis. At that time the work was not yet published, but now that it is, I want to draw your attention to a cool application of the Witkop-Winterfeldt oxidative indole cleavage. Upon C=C bond scission, transannular collapse leads to the formation of the cyclol structure shown below. This transformation is followed by azide-to-imine transformation mediated by triphenylphospine. The paper describes the synthesis of several indole alkaloids, of which I am only showing the molecule of mersicarpine. If you read the manuscript carefully, you will marvel at the application of the functional group pairing in order to arrive at some really intricate structures from a common starting material. It is too bad that I already gave my cumulative exam last week….
I have run Witkop-Winterfeldt oxidative indole cleavage on this substrate (X=TMS), to access 8-membered lactam intermediate, while repeating a published chemistry from Bertozzi group – and the indole scission worked really well (10g scale, nearly quantitative yield), with the indole N-allyl group surviving intact in the presence of mCPBA:
Thanks for sharing. 10 grams! I am impressed.