Can the conformational flexibility of cis-decalins be modulated through intramolecular O–H⋯O hydrogen bonding? Profiling the molecular and supramolecular attributes of designer cis-fused polycyclitols

In order to unravel the modalities of hydrogen bonding in conformationally flexible polycyclitols vis-à-vis their conformationally locked siblings, three diastereomeric perhydro-2,3,4a,6,7,8a-naphthalenehexols, all embodying a 4a,8a-dihydroxy-cis-decalin framework, have been synthesized via sequential stereo-controlled oxyfunctionalization of 1,4,5,8-tetrahydronaphthalene. Variable temperature NMR studies on the cis-fused polycyclitols thus obtained suggest that their inherent conformational flexibility in solution is restrained at ambient temperature owing either to the formation of a stable H-bonded molecular solvate or to the presence of strong intramolecular O–H⋯O H-bonding. Single crystal X-ray diffraction studies on the three hexols reveal an interesting commonality in their gross molecular packing and a ubiquitous presence of the R22(10) dimer motif—a supramolecular synthon rarely encountered in the crystal structures of conformationally locked and axially-rich hexols.

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