A computational study was initiated to probe the mechanism further. The study comprises two parts: one focuses on investigating the importance of the conformation of the TCA donor and the second focuses on locating a possible mechanistic pathway. To reduce the computational cost the benzyl groups were replaced with methyl groups. It was previously suggested by Nielsen et. al. that the differences in the degree of stereoselectivity between the α-TCA and the β-TCA are caused by the conformation of the imidate leaving group i.e. whether the imidate nitrogen is pointing "up" or "down". The full explanation can be found in the original paper by Nielsen et al., and an illustration of this initial explanation can also be found in SI (Section 4). To investigate this hypothesis a relaxed scan of the TCA group was carried out i.e. a geometry optimization for different frozen dihedral angles. The scans are illustrated in Figure . By looking at the TCA donors it is evident that a rotation around the imidate oxygen and the imidate carbon would lead to a change in the direction of the imidate nitrogen, this corresponds to changing the dihedral angle between the anomeric carbon, the imidate oxygen, the imidate carbon and the imidate nitrogen, here denoted (C-1)-O-C=N (blue arrow in Fig- ). However, for the β-TCA a rotation around the anomeric bond (red arrow in Figure ) would also lead to a change in the imidate nitrogen's position relative to the carbohydrate ring "plane", which is not the case for the α-TCA. Hence, two scans for the β-TCA were performed, while only one scan was performed for the α-TCA. It is seen in Figure top, that the conformation with the nitrogen pointing down is not a stable conformation for the α-TCA and is instead the transition state for the rotation around the bond. This is in line with early MM2 calculations by Schmidt. When rotating around the anomeric bond in the β-TCA a different picture is observed, as multiple minima are observed on the potential energy surface. It is seen that the global minimum (starting/end geometry) has the nitrogen pointing down with a slight twist toward the endocyclic oxygen. A local mini-mum with nitrogen pointing upwards is also observed at a dihedral angle of 60 degrees. For the (C-1)-O-C=N scan of the β-TCA a shallow minimum with nitrogen pointing up is also observed at 125 degrees. Interestingly, upon further rotation, the scan ends with an optimized geometry resembling the local minimum found in the anomeric bond scan of the β-TCA. In total three minima are found for the β-TCA, a global which has the nitrogen pointing down (Conformation 1 Figure ), and two local which have the nitrogen pointing up (Conformation 2 and Conformation 3 Figure ). To investigate the influence of the different conformations the Boltzmann distribution was calculated, and the probability of each conformation (p i ) can be found in Figure . It is seen that the distribution is heavily skewed towards Conformation 1. Based on these results it seems unlikely that two competing pathways starting from different conformations of the two TCA donors are the reason for the observed difference in selectivity as initially proposed. However, a difference in the favorability of trajectory for attack in the formed ion pairs, which was also a part of the initial explanation, could still play a role. To investigate this we sought to locate a (or multiple) possible mechanistic pathways on the potential energy surface.