Mollan, R. C. et al. published their research in Phytochemistry (Elsevier) in 1973 | CAS: 6639-06-1

3-(1H-Indol-1-yl)propanoic acid (cas: 6639-06-1) belongs to indole derivatives. The indole subunit is an almost ubiquitous component of biologically active natural products, and its study has been the focus of research for decades. It is used in perfumery and in making tryptophan, an essential amino acid, and indoleacetic acid (heteroauxin), a hormone that promotes the development of roots in plant cuttings.SDS of cas: 6639-06-1

Ultraviolet spectra of indoles in strong sulfuric acid was written by Mollan, R. C.;Harmey, M. A.;Donnelly, D. M. X.. And the article was included in Phytochemistry (Elsevier) in 1973.SDS of cas: 6639-06-1 This article mentions the following:

Measurement of the uv spectra in 12.7M H2SO4 at 30 and 70° provides a simple, quant. and specific method for the identification of variously substituted, naturally occurring plant indoles in μg quantities. In the experiment, the researchers used many compounds, for example, 3-(1H-Indol-1-yl)propanoic acid (cas: 6639-06-1SDS of cas: 6639-06-1).

3-(1H-Indol-1-yl)propanoic acid (cas: 6639-06-1) belongs to indole derivatives. The indole subunit is an almost ubiquitous component of biologically active natural products, and its study has been the focus of research for decades. It is used in perfumery and in making tryptophan, an essential amino acid, and indoleacetic acid (heteroauxin), a hormone that promotes the development of roots in plant cuttings.SDS of cas: 6639-06-1

Referemce:
Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study,
Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles