Modulating the preferred O-H...O hydrogen-bonding motif in a conformationally constrained environment through hydroxy-group derivatization.
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, C(38)H(34)O(10), 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, C(14)H(22)O(6), and (2R*,3R*,4aS*,8aS*)-4a,8a-dihydroxyperhydronaphthalene-2,3-diyl dibenzoate, C(24)H(26)O(6), have been analyzed in order to examine the preference of their supramolecular assemblies towards competing inter- and intramolecular O-H...O 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-H...O 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.
Mehta
Goverdhan
G
Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, Karnataka, India. gm@orgchem.iisc.ernet.in
Sen
Saikat
S