The title compounds (5a and 5b) were synthesized from ursolic acid and their structures were characterized by spectroscopic methods including ESI-MS, ¹H-NMR, ¹³C-NMR and elemental analysis. The crystal structures of compounds 5a and 5b were determined by single-crystal X-ray diffraction analysis. Compound 5a crystallizes in monoclinic system, P2₁ space group with a = 12.258(3), b = 10.396(2), c = 15.570(3) Å, b = 107.21(3)°, Z = 2, V = 1895.3(7) ų, M_r = 659.90, D_c = 1.156 Mg/m³, S = 1.003, µ = 0.076 mm⁻¹, F(000) = 716, the final R = 0.0686 and wR = 0.1430 for 1859 observed reflections (I > 2σ(I)). Compound 5b crystallizes in monoclinic system, P2₁ space group with a = 12.371(3), b = 10.647(2), c = 15.722(3) Å, b = 109.44(3)°, Z = 2, V = 1952.8(8) ų, M_r = 655.93, D_c = 1.116 Mg/m³, S = 1.002, µ = 0.069 mm⁻¹, F(000) = 716, the final R = 0.0686 and wR = 0.1882 for 2574 observed reflections (I > 2σ(I)). The preliminary cytotoxic assay indicated that compound 5b exhibited notable cytotoxic activity against MCF-7 and HeLa cells with the IC₅₀ values of 10.71 ± 0.23 and 12.63 ± 0.31 μM, respectively.