4,4'-[(2R*,3R*,4R*,5R*)-3,4-Dimethyl-tetra-hydro-furan-2,5-di-yl]diphenol.

The title mol-ecule, C(18)H(20)O(3), is a furan-oid lignan extracted from the leaves of Larrea tridentata. The relative absolute configuration for the four chiral centers was established, showing that this compound is 4-epi-larreatricin, which has been previously reported in the literature. The mol-ecule displays noncrystallographic C(2) symmetry, with the methyl and phenol substituents alternating above and below the mean plane of the furan ring. The conformation of this ring is described by the pseudorotation phase angle P = 171.3° and the maximum out-of-plane pucker ν(m) = 37.7°. These parameters indicate that the furan ring adopts the same conformation as the ribose residues in B-DNA. The packing is dominated by inter-molecular O-H⋯O hydrogen bonds. The phenol hy-droxy groups form chains in the [110] direction and these chains inter-act via O-H⋯O(furan) contacts.