syn-Dispiro-[1,3-dioxolane-2,17'-penta-cyclo-[12.2.1.1.0.0]octa-decane-18',2''-[1,3]dioxolane]-7',15'-diene.

The title compound, C(22)H(28)O(4), is composed of a central octa-decane ring and two spiro-[bicyclo-[2.2.1]hept[2]ene-7,2'-[1,3]dioxolane] units. This polycycle has pseudo twofold symmetry and the central cyclo-octane ring has a distorted boat configuration.

Tetra-kis(4-tert-butyl-benz-yl)silane.

The title compound, C(44)H(60)Si, was prepared as an inter-nal standard for diffusion-ordered NMR spectroscopy. The Si atom lies on a special position with site symmetry.