NMR experiments, which usually have a resolution of ≃ 2%, this value is certainly strikingly lower than all other theoretical estimates. This fact is even more important if one considers that β -d- Glc is supposed to have the largest $^{1}$C$_{4}$ free energy among aldopyranoses. It is thus expected that the $^{1}$C$_{4}$ conformers of the other stereoisomers could be characterized by even lower free energy differences. As it will be discussed in Sec.V, this scenario is only partially correct, as unexpected patterns of the chair–inverted chair free energy difference appear along the series. While the value of the free energy at the local minima is certainly interesting, a more direct connection with experimentally measurable quantities is performed through the cal- culation of the population of the basins associated with each of the recognizable conformers. To this aim, the ( θ, φ ) plane has been partitioned in four regions covering the four main basins: θ ∈ [0 , π/ 3], associated to $^{4}$C$_{1}$ ; θ ∈ [2 π/ 3 , π ], associated to $^{1}$C$_{4}$ ; θ ∈ [ π/ 3 , 2 π/ 3] and φ ∈ [ − 2 π/ 3 , 2 π/ 3], associated to 3 , $^{O}$B; θ ∈ [ π/ 3 , 2 π/ 3] and φ ∈ [2 π/ 3 , 4 π/ 3], associated to the mixture around $^{1}$S$_{3}$ . This partitioning of the conformational space appears to be quite natural, since the separating lines are located with good approximation along the maxima of the free energy surface (as is evident especially from the side-view of the free energy landscape, lower panel of Fig. 3) and, therefore, also close to the transition states. The population of a region S can then be calculated simply as where the integral of the normalization factor is extended to the whole ( θ, φ ) space. According to this numerical estimate, the $^{4}$C$_{1}$ , $^{1}$C$_{4}$ , 3 , $^{O}$B and $^{1}$S$_{3}$ conformations account for 98.42, 1.52, 0.0461 and 3.7 × 10 − $^{4}$% of the total population, respectively. When the manuscript was in preparation, we discovered that Hansen and H¨ uneneberger already performed an analysis of the puckering free energy of glucose $^{43}$. To our surprise, their estimates of the inverted chair free energy differ by a non-negligible amount from that presented here, although the same force field and thermodynamic conditions have been used. It has to be noticed that in the approach of Hansen and H¨ unenberger, free energies are derived from populations by inverting Boltzmann formula. We did the same and obtained a 14 Z = ∫ e − F ( θ,φ ) /k b $^{T}$dθdφ (9) p ( S ) = Z − 1 ∫$_{S}$ e − F ( θ,φ ) /k b $^{T}$dθdφ (8)