Studies On Configuration Transformation Of L-Proline And L-Valine

Amino acids are organic acids including amino and the fundamental unit of composing the protein. Besides glycine, amino acids are the chiral compound and have the configurations of L and D. D- amino acids are widely used in the fields of the food, the agriculture and the medicine. D- proline is an important intermediate of all kinds of optically active compound and pyrrolidine derivative,and is also one of important chiral reagents. D-valine is one kind of important organic chiral source, mainly applies in the chiral medicine, the chiral chemical additive, the chiral assistant and so on.The preparation of D-proline and D-valine by configuration transformation from L-proline and L-valine has been intensively studied.D-Pro·(R)-TA salt was obtained through the reaction of L-Pro with (R)-TA in n-Butyric acid with butyl aldehyde as catalyst. Treatment of the obtained salt D-Pro·(R)-TA with 35% ammonia in methanol gave D-Pro with the yield of 92.2% and the optical purity of 99.8% based on the starting L-Pro. The influences of temperature, time, carboxylic acid dosage and catalyst dosage on the yield and optical purity of D-Pro·(R)-TA and the infuences of alkali on preparation of D-Pro were discussed .The optimal process conditions are as following: reaction temperature 90℃, reaction time 6h, n-Butyric acid as solvent(15ml) and L-Pro:(R)-TA:butyl aldehyde =1:1:0.1(mol).L-valine could be racemized in carboxylic acids used as solvents in presence of aldehydes as catalyst. The experiment indicated the appropriate aldehyde and solvent for the racemization of L-valine should be salicyladehyde and acetic acid, and gave the optimal process conditions : reaction temperature 100℃, reaction time 3h, L-Val :salicyladehyde =1:0.1.DL-valine was obtained with the yield of 85.1% and 100% optical purity.DL-valine and the L- phenylalanine were dissolved in aqueous sodium hydroxide and the certain water. The pH was adjusted with the hydrochloric acid.DL-valine · L-...