Crystal structure of a new spiro-polytetrahydrofuran compound with translational pseudosymmetry: rac-(2S,2′S,5′R)-2-methyl-5′-[(1R,2R,5S,5′R)-1,4,4,5′-tetramethyldihydro-3′H-3,8-dioxaspiro[bicyclo[3.2.1]octane-2,2′-furan]-5′-yl]hexahydro[2,2′-bifuran]-5(2H)-one