A Theoretical and Experimental Investigation of Vicinal Tricarbonyl Systems and Their Hydrates

Article abstract of DOI:10.1021/jo00062a029

The conformational preference of the vinyl vicinal tricarbonyl reagent (VTC) and related triketones have been examined in the context of ab initio molecular orbital theory in order to better understand the properties of these reactive polyelectrophiles.The preferred conformation of the VTC methyl ester has been calculated to have the glyoxal unit twisted almost perpendicular to the plane of the ester unit.These results support the recent conclusions of Schreiber and co-workers on the activity of FK-506 and related compounds for inhibition of the rotamase enzyme.The origin of the enhanced reactivity has been examined via an analysis of the charge density distribution of the triketones and the corresponding hydrates.Electrostatic stabilization appears to be the main driving force for the stability of the hydrates.The energy of hydration for VTC has been calculated to be similar to that of activated aldehydes such as fluoral and chloral.Experimental values are also presented for the energy of hydration of chloral and VTC in acetone solution.