Conformational and reactivity study of dithiophenyl-fucosyl ketals with theoretical chemical methods

Carbohydrates can be used as substrates to synthesize new complex molecules; these molecules contain several chiral centers that can be used in organic synthesis. d-Fucose diphenyl thioacetal reacts differentially with acetone, and this paper describes a study of the mechanism of this reaction using theoretical chemistry methods. The conformer distribution was studied using a Monte Carlo method for the reaction products, and the obtained conformers were validated by calculating the hydrogen spin-spin coupling constants with the DFT/B3LYP/DGDZVP method. Results agreed with the experimental coupling constants with an adequate root mean squared deviation. The free energies and enthalpies of formation of the resulting global minimum conformers were calculated with the same method and with the thermochemical compound method CBS-4 M. This technique, combined with the conformational analysis, allowed comparison of the formation enthalpies of the compounds involved in this reaction, and, with this information, we can postulate the correct reaction pathway. [Figure not available: see fulltext.]