5,17-diethoxycarbonyl-25,26,27,28-tetrahydroxycalix[4]arene

The title compound, diethyl 25,26,27,28-tetrahydroxypentacyclo[19.3.1.1(3,7).1(9,13).1(15,19)]octacosa-1(25),3,5,7-(18),9,11,13(27),15,17,19(26),21,23-dodecaene-5,17-dicarboxylate, C34H32O8, a tetrahydroxy calix[4]arene, adopts an open-cone conformation in the solid state; this conformation is dictated by the presence of intramolecular O-H...O hydrogen bonding of the phenolic OH groups [O...O 2.673 (2)-2.708 (2) Angstrom]. The planes of the aromatic rings are inclined at 120.8 (1), 133.1 (1), 118.0 (1) and 128.5 (1)degrees to the plane of the methylene C atoms which link them. Self-inclusion occurs when the molecules assemble in pairs about inversion centres.