Puckering parameter

Note 2, A more precise specification of conformation can be achieved by use of the Cremer-Pople puckering parameters [22],... 

Figure 3. History of the Cremer-Pople pucker parameter calculated for the same trajectory illustrated in Figure 2. (Reproduced from Ref. 9. Copyright 1986 American Chemical Society.)...

Figure 6. History of the Cremer-Pople pucker parameter 6 calculated from molecular dynamics simulation of fi-D-glucopyranose in the Cj conformation in vacutim using the Rasmussen potential energy function PEF422. This molecule underwent four transitions in conformation. (Reproduced with permission from Ref. 11. Copyright 1987 Elsevier Science Publishers.)...

Cremer-Pople Puckering. Pyranose ring geometry is formally described by the Cremer-Pople puckering parameters Q, 0, and < )... 

Figure 9b. Observed and predicted Q puckering parameters vs. D. The range of observed values is quite small.

Figure 9d. The puckering parameter, plotted against D. At 435 A, the length for a perfect chair, changes from 60 to 240. ...

The geometry of the pyranoid rings of these compounds is that of a regular chair, as indicated by the Cremer-Pople69-70 puckering parameters (see Table I) and the ring-torsion angles. The inclination of the... 

Cremer-Pople Puckering Parameters for the 5-(Phenylphosphinyl)-L-idopyranoses and -L-iditol4... 

These are the well-known puckering parameters first defined by Cremer and Pople [205]. 

Monosaccharides exist chiefly in the six-membered pyranose form and in the flve-membered furanose form, both of which adopt puckered shapes to minimize eclipsing interactions. These puckered shapes are most commonly described in terms of the shapes of the symmetrical conformations adopted by the analogous hydrocarbons, cyclohexane and cyclopentane [8,9,10,11], but may also be described in terms of puckering parameters [12,13,14]. Minima on the conformational potential energy surface are called conformers. 

In accordance with the characteristics of conformer B, the thiazine ring in 92a assumes a skew-boat shape shifted somewhat toward the twist-boat form, whereas in 92b it has an almost perfect skew-boat conformation. The Cremer-Pople puckering parameters (< > = 89-%° and 0 = 69-77°) and the asymmetry factors for these conformations indicate a less (92a) and a more (92b) perfect symmetry axis bisecting the C-4—S-5 bond. Thus, the cw-fused triazoline ring with its N-2—C-3 double bond has an envelope conformation in 92a with the C-10 on the flap, but a halfchair conformation in 92b with a twofold axis bisecting C-3. Together,... 

Fig. 4.14. a, b Principal component plots derived for six-membered ring torsional datasets 6-C (1) and 6-C (2) respectively, c, d Plots of Cremer-Pople puckering parameters for six-membered ring datasets 6-C (1), 6-C (2) respectively... 

In this case, and indeed for all ring systems, the chemical meaning of the PC s now becomes obvious. The spherical conformational space of Figure 4.13 is related directly to the three Cremer-Pople puckering parameters 2>02> 3 [3]-... 

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