Sprince, Herbert published the artcileA modified Ehrlich benzaldehyde reagent for detection of indoles on paper chromatograms, Name: Potassium 1H-indol-3-yl sulfate, the publication is Journal of Chromatography (1960), 97-8, database is CAplus.
Indole chromatograms, sprayed first with a 2% solution of p-dimethylaminobenzaldehyde in 12.1N HCl, and, after 2-3 min., with 1% aqueous NaO2, show deep-blue spots which appear immediately. Indican appears as an orange-brown spot and urea as a large deep-yellow spot. Colors developed with this reagent often persist for at least a month without fading.
Journal of Chromatography published new progress about 2642-37-7. 2642-37-7 belongs to indole-building-block, auxiliary class Indole,Salt,Sulfonate,Inhibitor,Inhibitor, name is Potassium 1H-indol-3-yl sulfate, and the molecular formula is C65H82N2O18S2, Name: Potassium 1H-indol-3-yl sulfate.
Referemce:
https://www.nature.com/articles/s41429-020-0333-2,
Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles