Studies On Synthesis Of 4, 1', 6',-trichloro-4, 1', 6',-trideoxygalactosucrose By Using Monoesterification

Sucralose is a high intensive and none-nutritive sweetener with significant characteristics. In this paper, sucralose was successfully synthesized by using monoesterification with sucrose and triethyl orthoacetate as starting materials and vilsimier reagent as chlorination agent having highly selective. The effect of the molar ratio of materials, reaction temperature, reaction time, the amount of 4-toluene sulfuric acid catalyst and the sorts and amount of solvent on the experiment were investigated. The mechanisms of these reactions were also discussed.The optimal conditions for the reactions were summarized as follows:(1) The preparation of sucrose-6-acetate:At ambient temperature, in the presence of 4-toluene sulfuric acid catalyst with the amount of 6mg/g sucrose, the acetalization reaction can run smoothly for 3.5h, and the molar ratio of sucrose to triethyl orthoacetate was 1.0:1.3. After 3.5h, sucrose-4-acetate and sucrose-6-acetate were prepared by subjecting the sucrose ethyl 4,6-orthoacetate to hydrolysis for 35min with adding an amount of 4mL/40mLDMF water and 2mg/g sucrose 4-toluene sulfuric acid.35min later, t-butylamine was added with the amount of 2.5mL/100mLDMF, and the reaction was carried out for 4h with converting 4-acylate to 6-acylate. (2) The chlorination of sucrose-6-acetate:A suspension of sucrose-6-acetate in DMF solution was dropped to the mixture of ethyl acetate, DMF and Vilsimier regent (the volume ratio of ethyl acetate to DMF was 3:2, the molar ratio of Vilsimier reagent to sucrose-6-acetate was 10:1) at-10～0℃. The mixture was heated to 60℃in 45min and maintained at 60℃for 1h, and pyridine was added to neutralize the acid. Then the mixture was heated to 110℃in 2h by two steps and maintained for 3.5h, the reaction was stopped by quickly cooled to low temperature. (3) The sucralose-6-acetate deacetylation: The sucralose-6-acetate in methanol solution was evaporated under reduced pressure with adding sodium methoxide to adjust the mixture pH to 9～10 at ambient temperature for 4h. Being separated and decolorized, the total sucralose yield of this three-step reaction was 33%, and the purity of the product was up to 98%.