Abstract The X-ray crystallographic structure of the title compound, a product of a 1,3-dipolar cy cloaddition reaction of benzonitrile oxide to 3,3,4,4,5,5-hexamethyl-1,2-bis(methylene)cyclopentane, has been determined. Colourless plates crystallize in the orthorhombic space group Pbca with cell dimensions a = 13.698(2), b = 11.836(2), c = 29.157(4) Å, V= 4727.2(1.2)Å3, Z = 8, 3736 reflections, final R(F) = 0.063 and wR(F2) = 0.166. The crystals are racemic, the molecules of opposite chirality form centrosymmetric dimers via intermolecular hydro gen bonds O-H···N between their oxime groups. The molecules are highly strained and the geometrical consequences of the steric strain are discussed.
