Asymmetric flexibility

Reddy, A. L. M. et al. 2008. Asymmetric flexible supercapacitor stack. Nanoscale... 

Asymmetric, flexible hollow fiber carbon membrane with high mechanical strength was produced by thermooxidative stabilization and gradual carbonization of PAN based precursor membrane [11]. SEM showed that the itmer surface had the pores of 3-10 pm in diameter penetrating into the hollow fiber wall but not reaching the outer surface. Three membranes A, B, C were produced, the differ-... 

It is obvious, fipom some of the series of substituents in Table 7-11, that the steric constant reflects intuitive notions of group size, and Taft " pointed out close parallels with van der Waals radii. For asymmetrical groups a single van der Waals radius cannot be defined, and the situation is complicated by conformational flexibility. Nevertheless, empirical relationships can be established, and Kutter and Hansch gave Eq. (7-55),... 

Significant advance in the field of asymmetric catalysis was also achieved with the preparation of l,2-bis(phospholano)benzene (DuPHOS 4) and its confor-mationally flexible derivative (l,2-bis(phospholano)ethane, known as BPE) by Burk et al. [59]. Two main distinctive features embodied by these Hgands, as compared to other known chiral diphosphine ligands, are the electron-rich character of the phosphorus atoms on the one hand and the pseudo-chirality at phosphorus atoms, on the other. These properties are responsible for both the high activity of the corresponding metal complex and an enantioselection indepen-... 

LI ligase s large intrinsic flexibility was revealed by the recent crystal structure of the ligation product of a reduced size variant with two vastly different conformers, differing by reorientation of one of the stems by around 80 A, that were resolved in the same asymmetric cell [106], Based on the presence/absence of specific contacts between distant conserved parts including the ligation site and a totally conserved residue, U38, one of the conformers was postulated to represent the catalytically active or on conformation, the other the inactive or off one [106],... 

Along another line of work in our group (S,S)-l,4-bis(dimethylamino)-2,3-dimethoxy butane (DDB), which had been used as cosolvent in asymmetric synthesis [113], was tested as a core moiety for a dendritic amine catalyst. The conformationally flexible DDB-core, which has been synthesized in five steps from diethyl tartrate was coupled with different branches to give dendritically expanded diamines 90-92 (molecular weight 3800 Da) [114] (Fig. 32). 

In general, dendrimers of size G-0 through G-3 have open, asymmetric, and flexible structures with effectively no protected internal areas, due to a large freedom of motion in their branches, and they can readily accommodate additional covalent attachments to their surfaces. See Figures 73-7.5 for illustrations of the two-dimension and three-dimension structure of a... 

In chiral ligand 24, the two cyclopentane rings restrict the conformational flexibility of the nine-membered ring, and the four stereogenic centers in the backbone dictate the orientation of the four R-phenyl groups. Scheme 6 15 shows the application of Rh-24 in the asymmetric hydrogenation of dehy-droacylamino acids. 

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