Transformation of l-phenylalanine to (S)-indoline-2-carboxylic acid without group-protection

Determination and Correlation of Solubilities of (S)-Indoline-2-carboxylic Acid in Six Different Solvents from (283.15 to 358.15) K

“…We have disclosed two different routes to transform L-phenylalanine to SIn2CA: one includes successive nitration, bromination, and intramolecular cyclization sequence reactions 20 and the other is composed of successive dinitration, intramolecular cyclization, reduction, and diazonation reaction. 21 Although we have succeeded in the synthesis of SIn2CA from L-phenylalanine, as a continuation of research in this field, we found that there were still problems in the synthesis of SIn2CA for large scale application. For example, the SIn2CA obtained from L-phenylalanine was usually a pale-white power, and to obtain SIn2CA with high purity, especially high enantiomeric purity (enantiomeric excess), suitable solvent to realize the recrystallization of SIn2CA was needed.…”

“…As for the synthesis of unprotected SIn2CA, we have contributed in this field employing l -phenylalanine as a chiral pool. We have disclosed two different routes to transform l -phenylalanine to SIn2CA: one includes successive nitration, bromination, and intramolecular cyclization sequence reactions and the other is composed of successive dinitration, intramolecular cyclization, reduction, and diazonation reaction …”

Isolation of a Bacillus Aryabhattai Strain for the Resolution of (R, S)-Ethyl Indoline-2-Carboxylate to Produce (S)-Indoline-2-Carboxylic Acid

“…Researchers have also explored techniques that did not involve resolving agents. Liu et al nitrated L-phenylalanine to give 6-nitro-(S)-indoline-2-carboxylic acid, which was then reduced to give (S)-indoline-2-carboxylic acid [17]. These methods not only required high pressure or corrosion-resistant equipment, but were also highly polluting.…”