Category: indole-building-block

Yan, Chao published the artcilePotent activity of indolequinones against human pancreatic cancer: identification of thioredoxin reductase as a potential target, Computed Properties of 192820-78-3, the publication is Molecular Pharmacology (2009), 76(1), 163-172, database is CAplus and MEDLINE.

The indolequinone ES936 {5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione} was previously developed in our laboratory as an antitumor agent against pancreatic cancer. The objective of this study was to identify indolequinones with improved potency against pancreatic cancer and to define their mechanisms of action. Pancreatic cancer cell lines PANC-1, MIA PaCa-2, and BxPC-3 were used in in vitro assays [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) and clonogenic assays]; indolequinones displayed potent cytotoxicity against all three cell lines, and two specific classes of indole-quinone were particularly potent agents. These indolequinones induced caspase-dependent apoptosis but no redox cycling or oxidative stress in MIA PaCa-2 and BxPC-3 cells. Selected indolequinones were also screened against the NCI-60 cell line panel and were found to be particularly effective against colon, renal, and melanoma cancer cells. A potential target of these indolequinones was identified as thioredoxin reductase. Indolequinones were found to be potent inhibitors of thioredoxin reductase activity both in pancreatic cancer cells and in cell-free systems. The mechanism of action of the indolequinones was shown to involve metabolic reduction, loss of a leaving group to generate a reactive electrophile resulting in alkylation of the selenocysteine residue in the active site of thioredoxin reductase. In vivo efficacy of the indolequinones was also tested in the MIA PaCa-2 pancreatic tumor xenograft in nude mice, and lead indolequinones demonstrated high efficacy and low toxicity. Inhibition of thioredoxin reductase represents a potential novel target in pancreatic cancer and may provide a biomarker of effect of lead indolequinones in this type of cancer.

Molecular Pharmacology published new progress about 192820-78-3. 192820-78-3 belongs to indole-building-block, auxiliary class Fused/Partially Saturated Cycles,Dihydroindoles, name is 5-Methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione, and the molecular formula is C5H5F3O2, Computed Properties of 192820-78-3.

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

Grinshtain, Elina published the artcileThe Fer tyrosine kinase protects sperm from spontaneous acrosome reaction, Related Products of indole-building-block, the publication is Developmental Biology (Amsterdam, Netherlands) (2022), 24-33, database is CAplus and MEDLINE.

The physiol. acrosome reaction occurs after mammalian spermatozoa undergo a process called capacitation in the female reproductive tract. Only acrosome reacted spermatozoon can penetrate the egg zona-pellucida and fertilize the egg. Sperm also contain several mechanisms that protect it from undergoing spontaneous acrosome reaction (sAR), a process that can occur in sperm before reaching proximity to the egg and that abrogates fertilization. We previously showed that calmodulin-kinase II (CaMKII) and phospholipase D (PLD) are involved in preventing sAR through two distinct pathways that enhance F-actin formation during capacitation. Here, we describe a novel addnl. pathway involving the tyrosine kinase Fer in a mechanism that also prevents sAR by enhancing actin polymerization during sperm capacitation. We further show that protein-kinase A (PKA) and the tyrosine-kinase Src, as well as PLD, direct Fer phosphorylation/activation. Activated Fer inhibits the Ser/Thr phosphatase PP1, thereby leading to CaMKII activation, actin polymerization, and sAR inhibition.

Developmental Biology (Amsterdam, Netherlands) published new progress about 330161-87-0. 330161-87-0 belongs to indole-building-block, auxiliary class Protein Tyrosine Kinase/RTK,Src, name is SU6656, and the molecular formula is C19H21N3O3S, Related Products of indole-building-block.

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

Soderberg, Bjorn C. G. published the artcileIntramolecular cyclization reactions of unsaturated amino Fischer chromium carbenes forming indoles and quinolines, Product Details of C11H11NO2, the publication is Tetrahedron (2003), 59(44), 8775-8791, database is CAplus.

A thermally induced intramol. annulation reaction of N-(2-alkenylphenyl)amino substituted Fischer chromium carbenes has been extensively examined The carbene complexes were prepared in moderate to good yields by reaction of 2-aminostyrenes with intermediately formed acyloxy substituted carbenes. Upon heating, the thermally labile carbenes decomposed producing indoles and quinolines as the major products. The product distribution was found to be highly dependent on the substitution pattern and electronic properties of the starting material, and on the solvent used. The reaction of pentacarbonyl[1-[[2-ethenyl-3-(methoxycarbonyl)phenyl]amino]ethylidene]chromium gave 2-methyl-1H-indole-4-carboxylic acid Me ester. The reaction of pentacarbonyl[1-[[2-(1-methylethenyl)phenyl]amino]ethylidene]chromium gave 2,4-dimethylquinoline and 1,2,3,4-tetrahydro-2,4-dimethylquinoline.

Tetrahedron published new progress about 57663-18-0. 57663-18-0 belongs to indole-building-block, auxiliary class Indole,Ester, name is Methyl 2-methyl-1H-indole-5-carboxylate, and the molecular formula is C3H5BN2O2, Product Details of C11H11NO2.

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

Palani, Vignesh published the artcileA pyrone remodeling strategy to access diverse heterocycles: application to the synthesis of fascaplysin natural products, Name: 5-Methoxy-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indole, the publication is Chemical Science (2021), 12(4), 1528-1534, database is CAplus and MEDLINE.

The synthesis of diverse N-fused heterocycles, including the pyrido[1,2-a]indole scaffold, e.g., I, using an efficient pyrone remodeling strategy was described. The pyrido[1,2-a]indole core was demonstrated to be a versatile scaffold that could be site-selectively functionalized. The utility of this novel annulation strategy was showcased in a concise formal synthesis of three fascaplysin congeners.

Chemical Science published new progress about 683229-62-1. 683229-62-1 belongs to indole-building-block, auxiliary class Indole,Boronic acid and ester,Ether,Boronate Esters,Boronic Acids,Boronic acid and ester, name is 5-Methoxy-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indole, and the molecular formula is C15H20BNO3, Name: 5-Methoxy-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indole.

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

Blaikie, K. G. published the artcileMethoxyindoles and their derivatives, Name: Ethyl 7-methoxy-1H-indole-2-carboxylate, the publication is Journal of the Chemical Society, Transactions (1924), 296-335, database is CAplus.

2,5-O₂N(HO)C₆H₃Me, m. 128°, was obtained in 58 g. yield (together with 42 g. of 4,5-O₂N(HO)C₆H₃Me) by slowly adding 140 g. m-HOC₆H₄Me in 140 g. AcOH to a stirred mixture of 200 g. HNO₃ (d. 1.5) and 400 g. AcOH at -8° to -5°, and removing the 4-NO₂ derivative by steam distillation Me₂SO₄ (252 g.) added to 153 g. 2,5-O₂N(HO)C₆H₃Me and 46 g. Na in 750 cc. MeOH gave a 90% yield of 2,5-O₂N(MeO)C₆H₃Me (I), m. 55°. 2-Nitro-5-methoxyphenylpyruvic acid (II), yellow, m. 128° (phenylhydrazone, yellow, m. 151-2° (decomposition)), results in 51 g. yield from 50 g. of I and 63 g. (CO₂Et)₂ added to a suspn. of 35 g. EtONa in 300 cc. dry Et₂O. Oxidation of II by H₂O₂ in 2% NaOH gave 2-nitro-5- methoxyphenylacetic acid, m. 176°. Reduction of II in NH₄OH by FeSO₄ gave a 73% yield of 5-methoxyindole-2-carboxylic acid (III), m. 196-7° (evolution of gas). Warmed with Ehrlich’s reagent, a deep pink color is produced, which fades on cooling. Me ester, m. 177°. Et ester, m. 156°. 2,3-O₂N(MeO)C₆H₃Me, (CO₂Et)₂ and KOEt in Et₂O give a 75% yield of 2-nitro-3-methoxy-phenylpyruvic acid (IV), pale yellow, m. 161-2°, or yellow with 0.5 AcOH of crystallization, m. 118-45°. The EtOH solution gives a deep green color with FeCl₃, destroyed by mineral acids. Phenylhydrazone, yellow, m. 159° (decomposition). Oxidation of IV gives 2-nitro-3-methoxyphenylacetic acid, m. 137-8°, while reduction with FeSO₄ and NH₄OH gives 7-methoxyindole-2-carboxylic acid (V), m. 182° and decomposes on continued heating. Et ester, m. 114°. Me ester, m. 120°. 2-Nitro-6-methoxyphenylpyruvic acid (VI), yellow, m. 47-55°; phenylhydrazone, yellow, m. 173-4° (decomposition). Oxidation with H₂O₂ gives 2-nitro-6-methoxyphenylacetic acid, yellow, m. 172°, while reduction of VI gave 4-methoxyindole-2-carboxylic acid (VII), m. 234-5°, in 63% yield. Ehrlich’s reagent gives a purple color, which disappears on cooling. Me ester, m. 143.5°. Et ester, m. 161.5°. p-MeOC₆H₄NHNH₂ (VIII), best prepared by diazotizing p-MeOC₆H₄NH₂ and reducing with SnCl₂ in concentrated HCl, m. 65°; yield, 44%. α-Ketobutyric acid p-methoxy-phenylhydrazone (IX), yellow, m. 105°. o-Methoxyphenylhydrazone (X), pale yellow, m. 112°. The action of concentrated H₂SO₄ on IX (or the components in EtOH) gives 5-methoxyskatole-2-carboxylic acid (XI), m. 200-1° (decomposition), isolated as the Et ester, m. 151-2°; Me ester, m. 156°. In the same way X gave 7-methoxyskatole-2-carboxylic acid (XII), m. 222-3°, isolated as the Me ester, m. 144-15°, the yield of the acid being only 23%. A by-product of this reaction is Et ketobutyrate phenylhydrazone, yellow, m. 59-60°. III, changed to the acid chloride by PCl₅ in AcCl, this dissolved in CHCl₃ and treated with MeNHCH₂CH(OMe)₂, gave 5-methoxyindole-2-carboxydimethylacetalyl-methylamide, m. 159°. This is converted by warming with saturated alc. HCl at 40-50° for 15 min. into a mixt, of about equal amounts of 10-methoxy-3-keto-4-methyl-3,4-dihydro-4-carboline (XIII), m. 280°, has a distinct blue fluorescence in the solid state, gives a yellow HCl salt, which is dissociated by H₂O and gives no color with Ehrlich’s reagent or with vanillin and HCl in the cold; the alc. solution has a striking lilac fluorescence; and 10- methoxy-5-keto-4- methyl-4,5-dihydroindole-1,4-diazine (XIV), m. 243°, gives a greenish blue color with Ehrlich’s reagent, fading to a pale yellow on cooling and becoming green on boiling, and gives an intense purple color with vanillin and HCl; the EtOH solution has a very faint blue fluorescence which is not increased by adding HCl. 5-Methoxyindole-2-carboxyacetalylamide m. 151-2°, results from the chloride of III and H₂NCH₂CH(OEt)₂; Ehrlich’s reagent gives a purple solution, becoming intense blue on warming, while NaNO₂ produces a green color in the cold. Vanillin and HCl produce a deep pink which becomes intense bluish violet on the addition of NaNO₂ and warming. The action of alc. HCl gives 10-methoxy-5-keto-4,5-dihydroindole-1,4-diazine (XV), sinters 265°, m. 280°. 5-Methoxyindole-2-carboxydimethylacetalylamide, m. 154°, and with alc. HCl gives XV. 5-Methoxyindole-2-carboxyacetalylmethylamide, m. 127°, is formed from the chloride of III and MeNHCH₂CH(OEt)₂; with alc. HCl it yields about equal quantities of XIII and XIV. 7- Methoxyindole-2-carboxydimethylacetalylmethylamide, obtained only as a sirup, gives with alc. HCl a mixture of approx. 4 parts 12-methoxy-3-keto-4-methyl-3,4-dihydro-4-carboline, pale yellow, m. 250°, yielding a golden-yellow HCl salt, and 1 part 12-methoxy-5-keto-4-methyl-4,5-dihydroindole-l,4-diazine, m. 135°, which gives a blue color with vanillin and HCl and a green color with Ehrlich’s solution 4-Methoxyindole-2-carboxydimethylacetalylmethylamide, m. 112°, which, with alc. HCl, gave 9-methoxy-3-keto-4-methyl-3,4-dihydro-4-carboline, m. 250°, and yields a sparingly soluble yellow HCl salt. The mother liquors gave a green color with vanillin and HCl but the diazine was not isolated. When XII was subjected to the above reactions, a compound C₁₄H₁₃O₂N₂Cl, m. 190°, was obtained, which was unchanged by treatment with 10% MeOH-KOH for 10 min. and is probably 9-chloro-12-methoxy-5-keto-4,7-dimethyl-4,5-dihydroindol-l,4-diazine. III decomposes vigorously when heated to 205-210°, yielding 5-methoxyindole (XVI), b₁₇ 176-8° m. 55°, acquires a pink tint which slowly darkens on standing, is only slightly volatile with steam (1 g. per l. of H₂O), colors a pine shaving moistened with HCl reddish violet, gives a purple precipitate with concentrated HNO₃ and NaNO₂. Picrate, bright red, m. 145°. 1-Ac derivative (XVII), b₂₅ 210-1°, m. 80-1°. Nitration of the Ac derivative gave a mixture of an a-NO₂ derivative, light brown, m. 149°, soluble in EtOH, and the b-NO₂ derivative, brown, m. 213-4°, the a-derivative predominating. Hydrolysis gave a- and b-nitro-5-methoxyindoles, yellow, m. 144° (mixture m. about 112°); the a-form gives an orange-purple color with a pine stick, the b-form a deep purple. The a-form gives a pale red color with Ehrlich’s reagent, not affected by addition of NaNO₂, while the b-form develops a red color only after addition of NaNO₂. XVI, treated with CHCl₃ and EtOH-KOH, yields a mixture of 5-methoxyindole-3-aldehyde, m. 178°, and 3-chloro-6-methoxyquinoline, m. 73-4°, separated by steam distillation XVI was also synthesized as follows: 4-Methoxy-2-aldehydophenylglycineamide oxime, yellow, m. 196° (decomposition) was obtained in 70% yield from 5,2-MeO(H₂N)C₆H₃CH:NOH and ClCH₂CONH₂ (formyl derivative, bright yellow, m. 223°); on hydrolysis yields 4-methoxy-2-aldehydophenylglycine oxime, pale yellow, m. 178°; with saturated H₂SO₃ this is changed to 4-methoxy-2-aldehydophenylglycine, bright orange, m. 183° (decomposition) (phenylhydrazone, yellow, m. 175-6°) which yields XVII on boiling with AC₂O and AcONa. V, decomposed at 230-3°, gives 73% of 7-methoxyindole, b₁₇ 157°, b₂₁ 159-61°, slowly turns brown on keeping, fairly volatile with steam (2 g. per 500 cc. H₂O), gives a deep mauve pine-shaving reaction, gives a yellow color with Ehrlich’s reagent, deepening to orange-red on warming and to a deep reddish purple on addition of dilute NaNO₂. Picrate, red, m. 156°. With alc. KOH and CHCl₃ this yields 7-methoxyindole-3-aldehyde, m. 159-60°, and 3-chloro-8-methoxyquinoline, m. 84.5°; the yield of both products was small. VII, at 245-50°, gives 4-methoxyindole, m. 69.5°, (picrate, red, m. 159-60°) gives a deep purple pine-shaving reaction and a reddish purple color with Ehrlich’s reagent. XI decomposes at 210° and gives 75% of 5-methoxyskatole, m. 66°, apparently non-volatile with steam, gives a red pine-shaving reaction and a reddish purple color with Ehrlich’s reagent. Picrate, dark red, m. 151-2°. XII similarly yields 7-methoxyskatole, b₂₀ 170° (picrate, brownish red, m. 156°). The pine-shaving reaction is a deep purplish red; Ehrlich’s reagent gives no color in the cold; on warming a reddish purple color develops. The K derivative of II gives with Me₂SO₄ 2-nitro-α-methoxycinnamic acid (XVIII), pale yellow, m. 164-5°. Na salt, yellow. Me ester, pale yellow, m. 67°; the Et ester appears to be an oil. Oxidation of XVIII gives o-O₂NC₆H₄CHO. Reduction of XVIII with FeSO₄ and NH₄OH gives the 2-amino derivative, pale yellow, crystallines with 2AcOH and m. 167°. Me ester, yellow, m. 60-1°. The acid readily loses MeOH, forming indole-2-carboxylic acid, m. 203-4° (heating above its m. p., solution in cold concentrated H₂SO₄ at room temperature for 16 hrs., boiling with 10% HCl or reduction of XVIII with FeSO₄ and NH₄OH and boiling the reaction product for 24 hrs.). 2-Nitro-α,3-dimethoxycinnamic acid, from IV, as above, m. 202° (decomposition), and reduced to the 2-amino derivative, m. 139°, and decomposing above its m. p. to give V.

Journal of the Chemical Society, Transactions published new progress about 20538-12-9. 20538-12-9 belongs to indole-building-block, auxiliary class Indole,Ester,Ether, name is Ethyl 7-methoxy-1H-indole-2-carboxylate, and the molecular formula is C12H13NO3, Name: Ethyl 7-methoxy-1H-indole-2-carboxylate.

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

Kudo, Noriaki published the artcileA versatile method for Suzuki cross-coupling reactions of nitrogen heterocycles, COA of Formula: C15H14BNO4S, the publication is Angewandte Chemie, International Edition (2006), 45(8), 1282-1284, database is CAplus and MEDLINE.

A wide-ranging study of Suzuki reactions which use nitrogen-containing heterocycles was described. This method was highly versatile (a single procedure was used for all substrates, including boronate esters and trifluoroborates), compatible with a variety of unprotected functionalities (e.g., NH₂– and OH-substituted substrates), and efficient even with inactivated aryl chlorides.

Angewandte Chemie, International Edition published new progress about 149108-61-2. 149108-61-2 belongs to indole-building-block, auxiliary class Indole,Boronic acid and ester,Sulfamide,Benzene,Boronic Acids,Boronic Acids,Boronic acid and ester,, name is (1-tosyl-1H-Indol-3-yl)boronic acid, and the molecular formula is C15H14BNO4S, COA of Formula: C15H14BNO4S.

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

Yates, C. G. published the artcileNew intermediates and dyes. X. Preparation and reactions of 2-n-alkylquinizarins, SDS of cas: 2642-37-7, the publication is Journal of the Chemical Society (1965), 626-9, database is CAplus.

2-Methylquinizarin was prepared by hydrolysis of 4-chloro-l-hydroxy-2 methylanthraquinone, or better, from 1,4-diamino-2-methylanthraquinone and aqueous alk. dithionite. 2-Propyl-, 2-butyl-, 2- hexyl-, 2-heptyl-, and 2-octylquinizarin were derived by the interaction of leucoquinizarin and an aliphatic aldehyde: this reaction appeared to be limited, as the use of decyl- and dodecylaldehyde gave quinizarin only. Inhibiting effects of the 2-n-alkyl groups in reactions with amines were examined Thus, 2-methyl-, propyl-, and butylquinizarin and aqueous NH₃ gave some disubstitution of the hydroxy groups, but with derivatives of longer alkyl chain, only monosubstitution occurred; MeNH₂ afforded yellow fluorescent products, probably formed by loss of water from 2-alkyl-1,4-bis(methylamino)anthraquinones. Whereas cyclohexylamine gave excellent yields of 2-alkyl-1,4-bis(cyclohexylamino)anthraquinones, disubstitution was inhibited in reactions with PhNH₂, which gave monoanilino derivatives

Journal of the Chemical Society 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 C9H9ClN2, SDS of cas: 2642-37-7.

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

Londregan, Allyn T. published the artcileSynthesis of Pyridazine-Based α-Helix Mimetics, Recommanded Product: 6-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indole, the publication is ACS Combinatorial Science (2016), 18(10), 651-654, database is CAplus and MEDLINE.

A versatile synthesis of pyridazine-based small mol. α-helix mimetics is presented. Modular C-C, C-N, and C-O bond-forming reactions allow for the inclusion of a variety of aliphatic, basic, aromatic, and heteroaromatic side chain moieties. This robust synthesis is suitable for the preparation of small pyridazine-based libraries.

ACS Combinatorial Science published new progress about 642494-36-8. 642494-36-8 belongs to indole-building-block, auxiliary class Indole,Boronic acid and ester,Indole,Boronate Esters,Boronic acid and ester, name is 6-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indole, and the molecular formula is C14H18BNO2, Recommanded Product: 6-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indole.

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

Nakamura, Hiroshi published the artcileSensitive and specific detection of tryptophan, tryptamine and N-terminal tryptophan peptides on thin-layer plates using a unique fluorogenic reaction with fluorescamine, Recommanded Product: Potassium 1H-indol-3-yl sulfate, the publication is Journal of Chromatography (1978), 152(1), 153-65, database is CAplus.

Two sensitive and sp. methods were developed for the detection of tryptophan, tryptamine, N-terminal tryptophan peptides and other 3-(2-aminoethyl)-indoles on thin-layer plates in which the reaction is based on the unique fluorescence of the fluorescamine derivatives after treatment with HClO₄. The 1st method the compounds are separated on plates and reacted by dipping in acetone-n-hexane (1:4) containing fluorescamine, whereas in the 2nd method the compounds are first derivatized with fluorescamine at the origin of the plates by dipping in the solution and then separated When sprayed with 40% HClO₄, the fluorescamine derivatives appear as yellow-orange fluorescent spots. Certain 3,4-dihydroxyphenylethylamines and 3-methoxy-4-hydroxyphenylethylamines that have a free amino group in the side-chain also react, but they give a bluish fluorescence. Depending on the compounds, amounts of 1-800 pmole could be detected.

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 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

Nakamura, Hiroshi published the artcilePerchloric acid, a fluorogenic spray reagent for tryptophan, tryptamine, peptides containing tryptophan and other 3-substituted indoles, Application In Synthesis of 2642-37-7, the publication is Journal of Chromatography (1978), 152(1), 167-74, database is CAplus.

When silica gel plates containing 3-substituted indoles (e.g., 3-methylindole, indole-3-acetic acid), tryptophan derivatives, tryptamine, and tryptophan-containing peptides (e.g., H-Trp-Gly-OH, H-Pro-Trp-OH, H-Lys-Trp-Lys-OH) were sprayed with 70% HClO₄, a strong yellow-orange fluorescence developed. Other indole derivatives did not give this fluorescence when sprayed with 70% HClO₄. 3-Substituted indoles can be detected at 40-850 pmole by this method.

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 C8H6KNO4S, Application In Synthesis of 2642-37-7.

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