Structural Revision of an Indole Alkaloid Trichindole B through Synthesis of Three Isomeric Compounds

Herein, we report the first total synthesis and structural revision of the recently isolated natural product trichindole B (1). Discrepancies observed between the spectral data of the synthetic and natural product prompted us to do a structural re-evaluation, which was subsequently confirmed through the synthesis of target compounds bearing C5- and C6-isopentenyl substituents on the indole moiety. Detailed spectroscopic analysis revealed that the C6-isopentenyl regioisomer is in complete agreement with the reported spectral data of the natural product. Furthermore, we showed that routinely used tools such as Chemdraw can be handy for predicting and distinguishing positional isomers, thereby facilitating structural elucidation.