Synthesis And Mechanism Studies On L-Alanyl-L-Glutamine

L-glutamine(Gln) plays important role in the biosynthesis of Adenine, Guanine, Thymine, Cytosine, Uracil. Hence, for the patients, it is essential to provide them the Gln. However, Gln could not be included in currently available amino acid solutions due to its low solubility in water and the releasing of pyroglutamic acid and ammonia when it is under autoclave condition. Therefore, peptides cotaining Gin have taken place of Gln. For example, L-Alanyl-L-glutamine (Ala-Gin) has higer solubility and higher stability than Gin and is used as the infusion component.For the production of AlaGln, there are several kown methods, such as Yasutsugu Shimonishi method, N-carboxyl anhydride (NCA) method, DCC-HOSu method, Y -methyl L-glutamate method and D-2-halopropionic acid method.Recently, organic phosphorous coupling reagents have been applied for the synthesis of peptide derivatives. In this thesis activated ester could be synthesized through the Appel coupling reagents (triphenylphosphine and hexachloroethane) with N-(dialkyloxyphosphoryl)-alanine acid. Then the activated ester solution was added dropwise to the cooled solution of Gln in basic solution to give the product N-(dialkyloxyphosphoryl)-Ala-Gln. Finally the protective group was removed under dry hydrogen chloride to yield the target dipeptide Ala-Gin.In this thesis the reaction mechanism was also investigated. First, the coupling reagents were studied. Hexachloroethane was mixed with triphenylphosphine in different solvents under the protection of dry nitrogen, astraced by 31P-NMR. It was found that in different solvents the coupling reagents gave different chemical shifts. For example, in acetonitrile the reagents mixture gave the 31P NMR shift at 58.5 ppm, a peak at 24.8 ppm in DME, a strong peak at -39 ppm in dioxane. To prove the compositions of the coupling reagents, their MS were analyzed by ESI-MS. It was showed that a penta-coordinated phosphorous compound containing two chloro atoms PhsPCla was found in DME. In dioxane it seems that there was one molecule dioxane incooperated in the new species proposed as Ph3PCl(Dioxane). Second the carboxyl activated intermediates were also studied in the three solvents.Coupling of N-phosphoamino acids and sodium ammo acid by triphenylphosphine and hexachloroethane could produce sodium N-phosphopeptide. Similarly, N-phosphoamino acid, amino acid methyl ester, triphenylphosphine and triethylamine were dissolved in dichloromethane, then hexachloroethane in dichloromethane was added dropwise to the above cooled solution under the protection of dry nitrogen. As traced by 31P NMR, it was found that N-phosphopeptide methyl ester could be synthesized in one pot in reasonable yields.Various effects for scaled up synthesis of the AlaGln dipeptide was also investigated.