Phosphoric Acid → D-2-Amino-5-phenyl-pentanoic acid

Participants

Reaction Conditions

Reaction Steps

(±)-2-Amino-5-phenylpentanoic acid (35 g) was suspended in water (3 L) and solubilized by adjusting the pH to 12 with 7N sodium hydroxide solution. The pH was readjusted to pH 8 using 1M phosphoric acid with continuous stirring at 45° C. The solution was allowed to cool to 40° C. and L-amino acid oxidase (Sigma, 0.7 unit/mg) was added. The reaction was stirred with good aeration at 37°-40° C. for two weeks. The reaction was monitored using the following High Pressure Liquid Chromatography (HPLC) system: C-18 Waters analytical column, 20% acetonitrile in Buffer (0.624 g/L CuSO4.5H2O, 0.576 g/L L-proline, 2 g/L ammonium acetate, and 1L of water with the pH of the solution adjusted to pH 7 with ammonium hydroxide); 2 mL/minute flow rate; fluorescence detection: Ex 345 nm, Em>415 nm; OPA derivatization: 300 μL of 1N sodium borate pH 9.4, 50 mL of 20 mg ortho-phthalaldehyde (OPA) plus 24 ng N-acetyl cysteine/6 mL 50% methanol/water; incubate 3 minutes at ambient temperature. When the digestion of the L-enantiomer was complete, the reaction mixture was concentrated to 500 mL by removing water in vacuo. The pH was adjusted to 5 and the predpitate was collected by filtration and recrystallization from ethanol-water to afford 17.32 g (99%) of the title compound.

Provenance & Evidence