Tetra­methyl 1,4-dimethyl-13,14-dioxa­penta­cyclo­[8.2.1.1^4,7.0^2,9.0^3,8]tetra­deca-5,11-diene-5,6,11,12-tetra­carboxyl­ate

In the title compound, C₂₂H₂₄O₁₄, the relative stereochemistry at the cyclo­butane ring is cis-anti-cis and the methyl groups in the bicyclic rings are syn to each other. The two carboxyl­ate groups attached to the same —C=C— bond are disordered over two sets of sites in a 0.603 (2):0.397 (2) ratio. In the crystal, weak C—H...O hydrogen bonds connect mol­ecules into C(12) chains along [001] incorporating R₂²₂(10) rings.

Tetra-tert-butyl 13,14-dioxapenta­cyclo­[8.2.1.1^4,7.0^2,9.0^3,8]tetra­deca-5,11-diene-5,6,11,12-tetra­carboxyl­ate

The stereochemistry of the title compound, C₃₂H₄₄O₁₀, at the cyclo­butane ring is cis-anti-cis. The mol­ecule lies across an inversion center. In the crystal, weak C—H...O hydrogen bonds connect mol­ecules into chains along [100], forming R₂²(6) rings.

Hexamethyl 13,14-dioxapenta­cyclo­[8.2.1.1^4,7.0^2,9.0^3,8]tetra­deca-5,11-diene-1,4,5,6,11,12-hexa­carboxyl­ate

In the title compound, C₂₄H₂₄O₁₄, the stereochemistry at the cyclo­butane ring is cis-anti-cis and the –COOMe groups in the bicyclic rings are syn to each other. The mol­ecule lies on a twofold rotation axis. In the crystal, weak C—H...O hydrogen bonds connect mol­ecules into chains along [001], forming R₂²(10) rings.