Anraku, Takao published the artcileDecomposition of tryptophan by sulfurous acid salt. III. Isolation and structure of a greenish fluorescent product, Recommanded Product: Potassium 1H-indol-3-yl sulfate, the publication is Yakugaku Zasshi (1966), 86(11), 1043-50, database is CAplus and MEDLINE.
cf. preceding abstracts The substance which shows strong green fluorescence in a solution of tryptophan with a sulfite was isolated and presumed to be dehydroindirubin-1′,2,3,3′-tetrasulfonic acid tetra-Na salt (I). I was considered to be an intermediate in the formation of a red precipitate of indirubin from tryptophan. The formation of I explains well the changes of yellow coloration, green fluorescence to precipitation, and quenching of fluorescence to yellow coloration. It was assumed that the process of this decomposition followed hydrolysis of tryptophan to form indole, serine, and alanine, oxidation of indole with concurrent addition of sulfurous acid to form dehydroindigodisulfonic acid and dehydroindirubintetrasulfonic acid, and formation of various decomposition products by catalytic oxidation in the presence of H or OH ion.
Yakugaku Zasshi 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 C8H6KNO4S, Recommanded Product: 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