A Facile Chiral Pool Synthesis of (S)-6-Nitroindoline-2-carboxylic Acid from l-Phenylalanine

Abstract

S)-6-Nitroindoline-2-carboxylic acid, a substructure occurring in numerous biologically active natural products, was synthesized with moderate yield (53%) and high enantiomeric excess (>99.5%) starting from the nitration of L-phenylalanine, which is a commercially available chiral pool compound, followed by successively bromination and intramolecular cyclization. The route was carried out in gram quantities and it is suitable for industrial application due to its convenient reaction conditions and low cost.