Pseudorotational conformational wheel

Fig. 13. Conformational map of C-6-unsubstituted septanosides. Left A pseudorotational wheel of septanose conformations. Solid ovals mark conformations of P-septanosides, dashed ovals a-septanosides. Right Septanosides and the conformers that have been observed for them.

A particular ring conformer can be described by two parameters, the puckering amplitude (Xm) and the pseudorotational phase angle (P), which can be illustrated by the pseudorotational wheel shown in Figure 21 for a D-aldofuranose [106]. The radius of the circle is and P, which defines the part of the ring that is most puckered. 

Figure 3.6 shows the pseudorotation wheel with all possible puckers P of the sugar. A given value of P will automatically determine the conformational state of the sugar. Deviation from planarity will be determined by tw/ which will differ for each nucleoside. 

FIGURE 3.6 Pseudorotation wheel according to Altona and Sundaralingam. The E (envelope) and T (twist) conformations are those where one (E) or two (T) atoms are displaced from the mean plane. The number before the letter indicates the atom with the most dispiacement ... 

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