Linker groups

Since the discovery of SQ 83,360, compounds such as U-78,608 [123444-35-9] (64) having different linker groups between the hydroxypytidone group and the sulfonyl residue have been reported. U-78,608 and SQ 83,360 have similar in vitro and in vivo activity (45). 

Position of spacer arm. The position of the linker group on the target analyte that connects it to the immunogen has a profound influence on the selectivity and sensitivity of the subsequent assays. The handle should be attached as far as possible from the unique determinant groups, allowing maximum exposure of the important... 

Polymerization screening mns using porphyrin catalysts with different linker groups between the 700 Da polyethylene tail and the porphyrin core showed little variability. The catalytic activity for the 4 x 700 PE porphyrin catalysts with ether (5), ester (7) or polyether (8) linkers was nearly identical, with only small differences in the resin colors being noted (Figures 36.3 and 36.4). These results are consistent with literature findings that porphyrin CCT catalysts are relatively insensitive to functional groups on the equatorial plane. ... 

Figure 36.3. Catalyst activity of (PE7oo)4 -Co porphyrins as function of linker group.

Figure 36.4. MMA/BMA polymer solution eolor as funetion of linker group.

A number of bis(tacn) ligands, composed of pairs of covalently linked tacn macrocycles, can form similar structures, provided the linker group between the sandwiching macrocycles is sufficiently flexible (e.g., (556)).1411-1413 In particular, several Ni11 complexes of poly(tacn) derivatives with a central benzene have been studied, where the Ni is sandwiched between pairs of tacn macrocycles when these are attached to the ortho positions of the aromatic spacer group (e.g., (557)).1412,1413... 

The same urethane linker group that is a feature of conjugates 138 and 139 (Section 5.03.12) has also been used to provide SIN-1 13 conjugates of two vitamin E analogues, 6-tochopherol and Torolox , that undergo enzymatic bioactivation in the presence of porcine liver esterase to release nitric oxide <2006MI363>. 

For the synthesis of the peptide-protein conjugates, peptides with a readive linker group, ie a maleimido group at the N-terminal amino function, were required. The synthesis of these peptides... 

Obviously, the coordination of the new ligands is not affected by the additional linker groups at the bridging carbon atom. No coordination of the linker to the metal center instead of the carboxylate donor takes place and the geometries of the allyl group in 53 (Fig. 33a) as well as of... 

CSPs has, overall, a hydrophobic character (very similar to RP phases with C4-C8 ligands) which stems from contributions of the chiral selectors itself and (capped) linker groups (only a portion of the linkers are utilized for selector attachment) which constitutes a kind of hydrophobic basic layer on the support surface. Hence under typical RP-conditions, hydrophobic interactions between lipophilic residues of the solute and hydrophobic patches of the sorbent may be active and thus a reversed-phase like partition mechanism may be superimposed upon the primary ion-exchange process k = A rp -I- A ix). This A Rp-retention contribution may be especially important for eluents with high aqueous content. 

N-biotinylcaproylaminoethylmethanethiosulfonate (MTSEA-biotincap) is structurally related to MTSEA-biotincap, except that it contains a longer linker group (Seal et al., 1998). The length of MTSEA-biotincap that covalently links to the cysteine sulfhydryl is 20.0A (Teissere and Czajkowski, 2001). 

Biocatalyzed reactions on polymeric supports Enzyme-labile linker groups... 

In principle, linker groups are polymer-enlarged versions of blocking functions used in regular solution-phase chemistry. Therefore, enzymatic transformations that may be employed for the removal of protecting groups in solution, in principle may also open up alternative opportunities for releasing compounds from polymeric supports. The linkers developed so far can be divided into exo- and endo-linkers (Fig. 10.1) cleavable by exo- respectively endo-enzymes, as proposed by Flitsch et al. [6]. 

The linker group is immobilized as a urethane to the amino-functionalized carrier (59). It facilitates the attachment of a variety of molecules such as alkyl halides, alcohols or amines bound as carboxylic acid esters and amides. 

When the two uracil units are joined by a short N -linker group, 7 //-addition is prevented, and thus the 5-bromouracil derivative 466 gave the cis—syn cyclobutane photoadduct 467 as the major product in greater than 90% yield <2002TL5127>. 

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