Synthesis and α-Glucosidase Inhibitory Activity of Ursolic Acid, Lupeol, and Betulinic Acid Derivatives

Seven synthetic derivatives of ursolic acid, lupeol, and betulinic acid (1a–1b, 2a–2b, and 3a–3c) were synthesized to study their α-glucosidase inhibitory activity. Three of them (2b, 3b, and 3c) are new compounds. Among the synthetic derivatives, betulinic acid analogues 3b and 3c exhibited the best activity against α-glucosidase and is superior to the positive agent, with IC50 values of 35.0 ± 3.37 and 34.0 ± 1.24 μM, respectively.