Table of contents 1 Supplementary Figures ................................................................................................... 5 2 Supplementary Tables ................................................................................................... 21 3 Supplementary Methods – Experimental Section ...................................................... 54 4 Supplementary Methods – Synthetic Chemistry ........................................................ 60 4.1 General Information .................................................................................................. 60 4.2 Schemes for the preparation of indole carboxylic acids ........................................... 61 4.3 General Procedures for the preparation of indole carboxylic acids .......................... 66 4.4 Synthesis and Characterization of indole carboxylates and intermediates ............... 69 5 References ..................................................................................................................... 113 6 NMR Spectra ................................................................................................................ 115