Figure 1.

a) A pyranose ring in an idealized, symmetrical ⁴C₁ conformation. Atoms C4 and C1 are above and below the reference plane formed by atoms C2, C3, C5, and O5. Two additional planes can also define this conformation: b) with reference atoms C1, C3, C4, and O5 and c) with reference atoms C1, C2, C4, and C5. d) and e) show the planes illustrated in b) and c) from a different view. The reference planes for all other IUPAC shapes are given in Figure S2 and Table S2 in the Supporting Information.