We report on a combined experimental and theoretical study of the acid catalyzed dehydration of D-fructose in dimethylsulfoxide (DMSO) using; Amberlyst 70, PO43-/niobic acid, and sulfuric acid as catalysts. The reaction has been studied and intermediates characterized using; C-13, H-1, and O-17 NMR, and high resolution electrospray ionization mass spectrometry (HR ESI-MS). High level G4MP2 theory calculations are used to understand the thermodynamic landscape for the reaction mechanism in DMSO. We have experimentally identified two key intermediates in the dehydration of fructose to form HMF that were also identified, using theory, as local minima on the potential surface for reaction. A third intermediate, a species capable of undergoing keto-enol tautomerism, was also experimentally detected. However, it was not possible to experimentally distinguish between the keto and the enol forms. These data with different catalysts are consistent with common intermediates along the reaction pathway from fructose to HMF in DMSO. The role of oxygen in producing acidic species in reactions carried out in DMSO in presence of air is also discussed. (C) 2014 Elsevier B.V. All rights reserved.