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Subtle Crossover from C−H···O to SO···CO Short Contacts in the Association of Diastereomers of 2,4(6)-Di-O-benzoyl-6(4)-O-[(1S)-10-camphorsulfonyl]-myo-inositol 1,3,5-Orthoformate upon Formation of Pseudopolymorphs

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posted on 07.06.2006 by K. Manoj, Rajesh G. Gonnade, Mohan M. Bhadbhade, Mysore S. Shashidhar
Diastereomers of 2,4(6)-di-O-benzoyl-6(4)-O-[(1S)-10-camphorsulfonyl]-myo-inositol 1,3,5-orthoformate associate via weak interactions to form “head-to-head” dimers in their crystals. Molecular association through C−H···O short contacts do not leave any void for the guest inclusion, while association through SO···CO bridging produces pseudopolymorphs. Three crystalline modifications are observed for the title compound:  form I, monoclinic P21, without any guest solvent, and solvated forms II and III, that belong to monoclinic space groups P21 and C2, respectively. A majority of solvates, which include pyridine, dichloromethane, benzene, tetrahydrofuran, and cyclohexanone as guests, belong to form III. All these guests have 2-fold symmetry axes (C2) with their electron count within 40−62 electrons; guest selectivity experiments indicate that planar aromatic guests (pyridine, benzene) bind better to the host molecules as compared to nonplanar guests (dioxane, cyclohexanone). The molecular packing that is created thorough channels in the crystal (avoiding interpenetration of the layers) are of interest because of their potential application in molecular separation by forming selective inclusions. The diastereomeric association via SO···CO dipolar short contacts, a consistent feature observed in all the solvates, is thought to have relevance in the binding of sulfonyl drugs to the CO moieties of the receptor proteins.

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