Fine tuning the hydrophilic-hydrophobic balance in inositols through annulation: an analysis of the hydrogen-bonded architectures of 'annulated inositols'

Abstract

The crystal structures of conformationally locked, bicyclic cycloalkane-annulated variants of myo- and chiro-inositols have been analysed, in order to understand their mode of expression of the axial rich conformations and amphiphilicity in the solid state. Thus, while cyclohexaannulated myo- and chiro-inositols exhibit a head-to-head bilayer molecular assembly, consisting of dimeric or octameric columnar architectures, cyclopenta-annulated chiro-inositol shows no such aggregation of the hydrophilic and hydrophobic faces, rather preferring to pack in a manner akin to a hydrophilic inositol. The differences in the two packing modes can be attributed to the size of the hydrocarbon ring, fine-tuning the hydrophilic-hydrophobic balance in the annulated inositols. An analysis of the non-polar molecular surface area (a measure of the intermolecular hydrophobic van der Waals interactions) for all the annulated inositols under study further vindicates the conclusion.