Pseudosymmetry and phase transition in dimethyl 2,3-bis(tricyclo

The crystal structure of the title compound, C(26)H(34)O(4), shows a reversible phase transition at about 178 K. The structure of the high-temperature phase contains two independent molecules related by pseudosymmetry elements. Cooling through the phase-transition temperature results in a doubling of the c axis. The low-temperature structure contains four independent molecules related by pseudosymmetry elements. The phase transition results in a rearrangement of some weak intermolecular C-H.O interactions. The number of very weak C-H.O interactions, with H.O distances between 2.8 and 2.9 A, is increased in the low-temperature structure.