Total Synthesis of (+)-trans-Trikentrin A

Several syntheses have already been reported for cis‐trikentrins and herbindoles, which are indole alkaloids unsubstituted at the C2 and C3 positions that bear a trans‐1,3‐dimethylcyclopentyl unit. Herein, we describe the first asymmetric and stereoselective synthesis of the more challenging trans‐trikentrin A as its naturally occurring isomer. Different approaches were investigated and the strategy of choice was a combination of an enzymatic kinetic resolution and a thallium(III)‐mediated ring contraction. The antiproliferative activities of the natural product and related intermediates have been tested against human tumor cell lines, leading to the discovery of new compounds with potent antitumor activity. Simple target? Take a look again! The first stereoselective synthesis of a trans‐trikentrin is described (see scheme). In contrast, all cis‐related natural products have already been synthesized. An enzymatic kinetic resolution and a ring contraction are the key steps. Potent antitumor compounds have been discovered during this study.