Molecular modeling studies on the reduction of inososes and deoxy-inososes: a synthetic and historical overview of the cyclitols

The inososes are a group of compounds, containing six-membered rings that have five hydroxyls (four for the deoxyinososes) and a carbonyl. Due to the relative ease of their reduction to inositols, a study aimed at the potential preparation of these useful natural products was undertaken. The constitution of the hydroxyls shows that either the α or β face can react with an appropriate reducing agent, such as Raney Ni/H₂, to yield the expected inositol. It has been shown by others that, by using Raney Ni/H₂ as the reducing agent equilibrium between the two chair conformations can be established and the carbony! can be reduced stereoselectively. This is shown in the example below for allo-1-inosose:

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Molecular modeling with PCMODEL© which invokes MMX calculations was performed to permit a distinct prediction of the course and the stereochemical outcome of the reduction of the inososes.

Several inososes and deoxyinososes were modeled to demonstrate the ability of MMX calculations to predict the stereochemical outcome of the reduction. Based on the results of molecular modeling, which include the heats of formation, and the strain energies, the lowest energy form was determined for each inosose and deoxyinosose. With the lowest energy form predicted, stereochemistry of the inositol or deoxyinositol product was predicted. In one case, a comparison with known experimental results was made.