Crystal structure of a new spiro-polytetra-hydro-furan compound with translational pseudosymmetry: rac -(2 S ,2' S ,5' R )-2-methyl-5'-[(1 R ,2 R ,5 S ,5' R )-1,4,4,5'-tetra-methyl-dihydro-3' H -3,8-dioxa-spiro[bi-cyclo-[3.2.1]octane-2,2'-furan]-5'-yl]hexa-hydro[2,2'-bi-furan]-5(2 H )-one.

The title compound, C ₂₂ H ₃₄ O ₆ , is a product of oxidation of squalene with the catalytic system RuO ₄ (cat.)/NaIO ₄ . The asymmetric unit contains two crystallographically independent mol-ecules of very similar geometry approximately related by the non-crystallographic translation vector c /2. As a consequence, the average diffracted intensity in the hkl layers with odd l is systematically lower than in the layers with even l . In one mol-ecule, the lactone ring and part of the adjacent tetra-hydro-furan ring are disordered over two orientations with refined occupancy ratio of 0.831 (10):0.169 (10). The crystal structure is mainly governed by van der Waals forces.