Synthesis and crystal structure of maleopimaric acid

The title compound maleopimaric acid was synthesized by a Diels–Alder reaction between maleic anhydride and Pinus elliottii engelm oleoresin at room temperature and it was characterized by single crystal X-ray diffraction. The white crystals crystallized in the orthorhombic system, space group P2 12121 with cell dimensions: a = 7.6960 (15) Å, b = 11.851 (2) Å, c = 24.577 (5) Å, α = 90°, β = 90°, γ = 90°, V = 2241.6(8) Å3, and R 1 = 0.0716, wR 2 = 0.1975. The two fused and unbridged cyclohexane rings form a trans ring junction with chair conformation with two methyl groups in axis positions, the anhydride ring is planar. Crystal water existed in the molecular and stabilized the structure through intermolecular hydrogen bonds.