Crystal structure of a new spiro-polytetra-hydro-furan compound with translational pseudosymmetry: rac-(2S,2'S,5'R)-2-methyl-5'-[(1R,2R,5S,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(2H)-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.