2-Chloro-L-phenylalanine

3752-25-8

103616-89-3

The general steps for the synthesis of L-2-chlorophenylalanine from 2-chlorocinnamic acid were as follows: first, based on the phenylalanine amino lyase (PAL) protein sequence of Rhodosporidium toruloides ATCC 10788 (NCBI Protein Data Bank No. CAA31209), the Genscript Corporation to synthesize the PAL gene of R. glutinis and codon optimized for E. coli expression. The synthesized PAL gene was ligated to the SmaI site of the pUC57 vector by Genscript to construct the pUC57_PAL plasmid. 5 μg of lyophilized pUC57_PAL plasmid was dissolved in 50 μl of MilliQ water, and 1 μl of the solution was taken to transform E. coli DH5α chemoreceptor cells according to the supplier's protocol. The transformed cells were cultured on LB solid medium containing 100 μg/ml carbenicillin at 37°C overnight. Single colonies were selected for inoculation in 20 ml of LB liquid medium containing 100 μg/ml carbenicillin, prepared in 8% glycerol and stored at -80°C. The DH5α strain containing pUC57_PAL was inoculated in 1000 ml of LB medium containing 100 μg/ml carbenicillin and incubated at 28°C overnight. Subsequently, the culture was inoculated in 10 liters of TB medium (containing 0.1 g/l carbenicillin and 1 mM IPTG) and fermented with agitation at 37°C for 9.5 hr at 500 to 1500 rpm. Cells were collected by centrifugation to obtain 230 g of wet cells, which were dispensed into 10 g aliquots stored at -20°C. Prior to the reaction, an appropriate amount of cells was thawed and resuspended in cold water. 1.8 g (10 mmol) of 3-(2-chlorophenyl)-acrylic acid was dissolved in 0.5 L of 13 vol% aqueous ammonia solution, and the pH was adjusted to 11 with 25 w/w% H2SO4. 130 g of wet cells were resuspended in 0.2 L of 13 vol% aqueous ammonia solution of pH 11, mixed with the substrate solution, and the total volume was adjusted to 1 L. The reaction was carried out at 30 °C in a closed 200 rpm vessel. Initially 0.91 g (5.0 mmol) of 3-(2-chlorophenyl)-acrylic acid was added every 5 min for 1 h and the same amount was added every 25 min for the next 7 h. After 8.5 h, the cells were removed by centrifugation and the reaction yield was determined by HPLC to be about 91%, yielding about 18.1 g (91 mmol) of 2-chlorophenylalanine. The supernatant (850 mL, pH 10.8) was concentrated under reduced pressure (150 to 10 mbar, 60 °C) to form a precipitate (pH 7.5) after removal of about 65% water. The precipitate was filtered, washed with water to remove inorganic salts, and dried to give 14.9 g of product containing 57 w/w% N-amino-3-(2-chlorophenyl)-propionic acid (8.5 g, 47% yield), 24 w/w% water, and 1.7 w/w% 3-(2-chlorophenyl)-acrylic acid. The enantiomeric excess (e.e.) of (S)-2-amino-3-(2-chlorophenyl)-propionic acid was 99%. 9.5 g of (S)-2-amino-3-(2-chlorophenyl)-propionic acid remained in the mother liquor.