The Chemical Synthesis Of Glutathione

Glutathione (GSH) is a biologically active thiol tripeptide havingγ-glutamyl acyl and anino.GSH protects cells against stimulation and threats from outside environmental conditions. In addition,.GSH has a variety of important bio-physiological functions in biologic body, especially to maintain an appropriate vivo redox environment. On account of its wide range of biological effects, GSH not only has been widey used in the medical and biological industries, But also has an optimum potential in food additive industry. here is significantly economic value to design a straightforward and practical synthesizing method of GSH, which can besimply manipulated at lower cast and yield high purity GSH.In this paper, glutathione is synthesized through chemical method, cysteine is firstly synthesized with glycine to obtain dipeptide, and then dipeptide is combined with glutamic acid to form three peptidesIn order to avoid side reactions in the process of synthesis of two peptides two different protection groups are used to preserve the acid N-terminal on the amino.In the first method benzyl chloride is used to protect L-cysteine thiol, Tert-Butoxycarbonyl (Boc) is selected as the amino protection group, and S-benzyl-N-Boc-L-cysteine is obtained through the reaction condition under the conditions that: 1)the beginning temperature is -1-1℃; 2) the reaction last for 4 hours; and 3)reactant molar ratio was 1:1. Then S-benzyl -N-Boc-L-cysteine is synthesized with the glycine ethyl ester to form S-benzyl - N-Boc-L-cysteinyl glycine ethyl ester under the conditions of DCC. In the solution of 50% F₃CCOOH-CH₂Cl₂, N-terminal protecting groups Boc is off and finally obtains dipeptides—S-benzyl-cysteinyl glycinate.In the second method, benzyloxycarbonyl (Cbz-) is used to protecte amino, resulting S-benzyl-N-Cbz-L-cysteine. Then S-benzyl-N-Cbz-L-cysteine is used to compound with the glycine ethyl ester to form amide bond containing the dipeptides S-benzyl-N-Cbz-L-cysteinyl glycine ethyl ester under the conditions of DCC. Cbz protecting groups are off in the acetic acid solution of hydrogen bromide, and finally S-benzyl-Cys-Gly is obtained.Boc as the amino protection group has its own merits: 1) it is not prone to racemization; 2) it has higher yield; and 3) it is simple for manipulation and separation. In addition, it is conwenient to remove the amino protecting group Boc in the CH₂Cl₂-F₃CCOOH solvent afher the reaction.Before synthesizing the three petide synthesis, it is important to protect the active amino,α-carboxyl of glutamate's by taking the advantage of the stable sixmembered ring anhydride dehydrated from glutamic acid, so that the nucleophile attack on the selectivity ofγ-acyl increase and it is beneficial for the formation of three peptide. Six-membered ring anhydride can be obtained through the reaction using DCC as dehydrating agent at low temperature or using acetic anhydride under the condition of heated reflux.Lastly, take off mercapto-protecting group and glutathione, the target product, is obtained. The chemical structures of the glutathione has been characterized by 1H NMR, IR and melting point.The study also explores the application of microwave method in the reaction of de-protection of amino, and the study result indicates that microwave method reaction time to off N- protection, increases productivity and optimizes reaction conditions.