Two diastereomers of (+-)-cis-2-(3-oxo-1,3,4,5,6, 7-hexahydroisobenzofuran-1-yl)cyclohexanecarboxylic acid

The structures are presented for both diastereomers of the title compound, C(15)H(20)O(4), produced by base-catalyzed self-condensation of cyclohexane-cis-1,2-dicarboxylic anhydride in refluxing triethylamine. Equilibration of either diastereomer under the condensation conditions yielded the same 5:3 mixture. In the crystal, one diastereomer, (II), is ordered, while the other, (I), displays both flexional ring disorder and carboxyl disorder; both aggregate as centrosymmetric hydrogen-bonded dimers [for (I), O.O = 2.680 (2) A; for (II), O.O = 2.635 (4) A].