Modulating the preferred O-H···O hydrogen-bonding motif in a conformationally constrained environment through hydroxy-group derivatization

Abstract

The crystal structures of three conformationally locked esters, namely the centrosymmetric tetrabenzoate of all-axial perhydronaphthalene-2,3,4a,6,7,8a-hexaol, viz. trans-4a,8a-dihydroxyperhydronaphthalene-2,3,6,7-tetrayl tetrabenzoate, C₃₈H₃₄O₁₀, and the diacetate and dibenzoate of all-axial perhydronaphthalene-2,3,4a,8a-tetraol, viz. (2R^∗ ,3R^∗,4aS^∗,8aS^∗)-4a,8a-dihydroxyperhydronaphthalene-2,3-diyl diacetate, C₁₄H₂₂O₆, and (2R^∗,3R^∗,4aS^∗,8aS^∗)-4a,8a-dihydroxyperhydronaphthalene-2,3-diyl dibenzoate, C₂₄H₂₆O₆, have been analyzed in order to examine the preference of their supramolecular assemblies towards competing inter- and intramolecular O-HO hydrogen bonds. It was anticipated that the supramolecular assembly of the esters under study would adopt two principal hydrogen-bonding modes, namely one that employs intermolecular O-HO hydrogen bonds (mode 1) and another that sacrifices those for intramolecular O-H...O hydrogen bonds and settles for a crystal packing dictated by weak intermolecular interactions alone (mode 2). Thus, while the molecular assembly of the two crystalline diacyl derivatives conformed to a combination of hydrogen-bonding modes 1 and 2, the crystal packing in the tetrabenzoate preferred to follow mode 2 exclusively.