ON THE RACEMIZATION OF N-PROTECTED ACTIVE ESTERS OF PHENYLALANINE UNDER THE INFLUENCE OF AMINES

Add time:09/29/2019    Source:sciencedirect.com

Publisher SummaryThis chapter discusses the racemization of N-protected active esters of phenylalanine under the influence of amines. The benzyloxycarbonyl group protects the adjacent asymmetric carbon atom from racemization. The p-nitrophenyl, 2,4,6-trichlorphenyl, phenyl and cyanomethyl esters of benzyloxycarbonyl-L-phenylalanine are racemized under the influence of triethylamine. The extent of this racemization is related to the time of action, to the concentration of the t-amine and also to the strength of the activation. The aminolysis of the fast esters does not lead to epimerization. Epimerization can be observed during the aminolysis of the slow phenyl and cyanomethyl esters. However, the last epimerization can be avoided, if the aminolysis of the slow esters is accelerated by the use of amino-acid t-butyl ester as the amino component and by adding equimolecular amounts of acetic acid. The racemization of the nitrophenyl ester of formyl- phenylalanine runs partially through an azlactone and partially through the dissociation of the α-hydrogen. The racemization of the benzyloxycarbonyl-L-phenylalanine nitrophenyl ester, induced by triethylamine, can have the same mechanism.

We also recommend Trading Suppliers and Manufacturers of N-(Benzyloxycarbonyl)-L-serine 4-nitrophenyl ester (cas 1676-91-1). Pls Click Website Link as below: cas 1676-91-1 suppliers

Prev:Studies on amino acids and peptides—I : Synthesis of N-benzyloxycarbonylendo-thiodipeptide esters
Next:Preparation and characterization of thiophilic cryogels with 2-mercapto ethanol as the ligand for IgG purification)