Abstract: Trimethyl maleopimaric acid was synthesized in an autoclave using 3A molecular sieve as a dehydrating agent. The optimum technological conditions are as follows: maleopimaric anhydride 4 g (0.01 mol), 3A molecular sieve 5.4 g, methanol 11.6 g (0.36 mol) and ZnO 0.02 g were added into an autoclave, and temperature was hold at 250℃ for 4 h. Under these condition, the yield of trimethyl maleopimaric acid was 98%, acid value was 18.5 mg/g and esterification degree of product was 2.85. FT-IR and NMR were utilized to determine the structure of the product. It was confirmed that the structure of the product was the same as target product. According to ¹H NMR data the purity of trimethyl maleopimaric acid was 84%. The acid value of the product can be reduced dramatically by adding molecular sieve.

Key words: maleopimaric anhydride, esterification, trimethyl maleopimaric acid, molecular sieve