Fig. 4. Lowest energy structures and their relative Gibbs free energies at 298 K (G_rel) and Boltzmann-averaged dipole moments μ [D] of trans and cis conformers of Ac-Pro-OMe (1-OMe) and Ac-Pro-NMe₂ (1-NMe₂) calculated with CHCl₃ as solvent at the PBE0-D3-COSMO/def2-TZVP level of theory. For clarity, only the values of the C(4)-endo conformers are listed. The values hardly change when also the C(4)-exo conformers are taken into account, see the ESI.† .