Thermal epimerization of inositol 1,3-benzylidene acetals in the molten state

Abstract

1,3- O-Benzylidene-2,4,5,6-tetra- O-substituted- myo-inositol derivatives obtained by the DIBAL-H reduction of the corresponding myo-inositol 1,3,5- orthobenzoate derivatives undergo epimerization at the acetal carbon on heating, in the molten state, just above their melting point. The same epimerization reaction does not proceed either in the crystalline state or in solution. DFT calculations suggest that the epimeric acetal obtained by this thermal process is relatively more stable than the starting acetal. Either of these acetals could not be obtained by the reaction of the corresponding inositol derived diol with benzaldehyde. These observations constitute a novel reaction solely in the molten state, which are rarely encountered in the literature. X-ray crystal structures of the epimeric acetals as well as their radical deoxygenation reaction are also reported.