Study On The Synthesis Of N,N-Diacetyl-L-Cystine

N,N'-diacetyl-L-cystine is the key intermediate for the preparation of N-acetyl-L-cysteine by L-cystine.The synthesis process of N,N'-diacetyl-L-cystine from L-cystine was studied in this thesis.First,the reacting material L-cystine was dissolved into alkali solution,acetic anhydride used as acetylation reagent and controlled pH value by alternately dropping the acylating reagent and alkali.After acetylation reaction,the product mixture was neutralized and concentrated by evaporation.The compound of N,N'-diacetyl-L-cystine was successfully obtained after the crude product was further treated with a series of steps such as dissolution,filtration,purification,and drying operation.The product was analyzed with HPLC under the following conditions: the mobile phase being V(phosphate buffer solution):V(methanol)= 85:15,the wavelength of the ultraviolet detector being 214 nm,the column temperature being 30 ?,the flow rate of the mobile phase being 0.5 mL/min,and the injection amount being 20 ?L.The results of nuclear magnetic resonance and mass spectrum indicate that the structure of the synthesized product is consistent with the chemical structure of N,N'-diacetyl-L-cystine.Some factors including the type of acetylation reagent,the purification method,pH value,reaction temperature,the ratio of reactants and reaction time were also investigated to show their influences on the yield of N,N'-diacetyl-L-cystine.The optimum process parameters obtained by orthogonal experiments were as follows: reaction temperature being 0 ?,pH being10,the molar ratio of L-cystine to acetic anhydride being 1:4,and reaction time being1 h.Finally,the synthesis experiment of N,N'-diacetyl-L-cystine was enlarged step by step to kilograms scale to further optimize the process parameters,which is helpful for the commercial production of N,N'-diacetyl-L-cystine in future.