The torsion free energy profile of oxazole-4-carbaldehyde N-C-C-O dihedral angle was obtained by performing umbrella simulations at the MM, ML/MM and QM/MM levels, using 50 ps long NVT simulations (300 K) for every case. Starting structures for each window were obtained from a steered molecular dynamics simulations. A force constant of 200 kcal/(mol rad 2 ) was used in each case and windows were spaced by 5 degree each.