Synthesis and transfer rate of thymol-β-D-glucopyranoside
[Background]This study aim to improve the thermal stability of thymol by conducting glycosylation research.[Methods]Acetyl bromide-α-D-glucose(Ⅰ)and thymol(Ⅱ)were reacted under ionic liquid catalysis to synthesize thymol-2,3,4,6-tetra-O-acetyl-β-D-glucoside(Ⅲ),and compound Ⅲ was deacetylated to obtain thymol-β-D-glucoside(Ⅳ).The thermal stability of compound Ⅳ was investigated through TG-DTG,its pyrolysis behavior was studied through Py-GC-MS,and the pyrolytic transfer rate of compounds Ⅱ and Ⅳ in the particulate phase of mainstream smoke,as well as the change in transfer rate over time,was researched through GC-MS.[Results]The reaction conditions for the catalytic synthesis of compound Ⅲ using ionic liquids were as follows:sodium hydroxide aqueous solution as acid binding agent,1-butyl-3-methyl-bromimidazolium as catalyst,dichloromethane as solvent,n(Ⅰ):n(NaOH)=1:2,n(Ⅰ):n(1-butyl-3-methyl-bromimidazolium)=1:1,n(Ⅰ):n(Ⅱ)=1:1,reaction time 4 hours,with a yield of 55.1％for compound Ⅲ.Under the action of sodium methoxide,compound Ⅲ was deacetylated to obtain the target glucoside Ⅳ,with a yield of 80.6％.The structure of the product was confirmed by 1HNMR,13CNMR,IR,and HRMS.The thermal stability of compound Ⅳ was superior to that of compound Ⅱ,and the main pyrolysis products of compound Ⅳ at different temperatures were compound Ⅱ,indicating that the fragrance stability of compound Ⅳ was superior to that of compound Ⅱ.[Conclusion]Thymol-β-D-glucoside can improve the drawbacks of thymol and can be used as a thermally stable and fragrance-stable precursor for tobacco flavoring.
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