Linkers phenyl

Hydrazone of 1 -hydrazino-1 -hydroxy-4-phenyl-1,2-dihydro-3//-pyrido [l,2-c]pyrimidin-3-one was patented as cross-linkers for making physiologically compatible and H2O insoluble hydrazine or hydrazono compounds (97JAP(K)97/59303). 

TFA) in DCM (dichloromethane). Linkers for carboxylic acids have also been designed to effect cleavage via photolysis (3-nitro-4-hydroxymethylbenzoic acid, ONb 14) [18] and flouridolysis (N-3 or 4) ((4-hydroxymethyl)-phenoxy-t-butylphenylsilyl)phenyl pentanedioic acid monoamide (PBs) 15 [19] and quinonemethide-based handle 16 [20] (Fig. 

Meisenbach M, Echner H, Voelter W. New methoxy-substituted 9-phenyl-xanthen-9-ylamine linkers for the solid phase phase synthesis of protected peptide amides. Chem Commun (Cambridge) 1997 849-850. 

After isolating the product of a solid phase synthesis, the support (resin + linker) is usually discarded as waste, although successful examples of its reuse in further synthetic cycles are known with trityl type linkers (Frechet and Haque 1975). To reduce both volume of operation and amount of waste, the loading of the resin (quantified as millimoles of functionality per gram) has to be increased. Besides theoretical limitations (for polystyrene this is reached when every phenyl ring is substituted by the linker), there may be practical boundaries for using highly loaded resins in solid-phase supported synthesis. This issue was studied... 

The notion of stabilized and sensitized protectors is pertinent to solid-phase synthesis in particular. Practically all of the linkers through which carboxy-terminal residues are attached to the solid support are composed of benzyl that has been substituted with functional groups such as dialkoxy, dimethoxyphenyl, phenyl (ben-zhydryl), diphenyl (trityl), chlorodiphenyl (chlorotrityl, see Section 5.23), or other to modify the stability of the linking bond.9-63-73... 

There are dozens of linkers available for synthesis, and nearly all of them, once acylated by a protected amino acid, provide a benzyl ester or a benzyl amide that has been sensitized to cleavage by acid by the presence of electron-donating moieties such as alkoxy, phenyl, or substituted phenyl. There are cases in which a peptide chain is bound to a support through two different linkers in series. This allows for versatility in synthesis. The distinction between designation of a moiety affixed to a support as a handle or linker is sometimes arbitrary. 

FIGURE 5.17 Resins and linkers for synthesis of peptides using Fmoc/tBu chemistry. The linkers are secured to supports by reaction with aminomethyl resins. A protected amino acid is anchored to the support as an ester by reaction with a hydroxyl or chloro group (italicized). The alkoxy and phenyl substituents render the benzyl esters sensitive to the cleavage reagents. 

A modified rare earth catalyst (30) which is based on a polystyrene backbone as depicted in Scheme 4.15 can be applied even in neat water. It is attached via a hydrophobic oligomeric linker which creates a nonpolar reaction environment and acts as a surfactant for the substrates. The reaction of 4-phenyl-2-butanone with tetraallyltin in water using 1.6 mol% of the scandium catalyst (30) afforded the corresponding homoallylalcohol in a yield of 95%. Interestingly, when using other solvents (dichloromethane, acetonitrile, benzene, ethanol, DMF) the yields decreased drastically, indicating a much higher reaction rate in water [98]. 

Carbosilane dendrimer [G1] with 4-(hydroxymethyl)phenyl linker... 

Turning attention to the phenyl hydroxamic acids, these are a relatively sparsely explored series of HDACi, probably due to the fact that simple analogs are somewhat less potent HDACis compared to alkyl or cinnamyl linkers. Nevertheless, the group at Celera Genomics was able to identify the phenyl hydroxamic acid 27a,... 

Syntheses of this class of compounds usually involve 1,2,5-thiadiazepine ring 333 (Figure 6) which is stable in the S-oxidized form and structurally represents cyclic pyrrole N-sulfonyl derivatives. Most of the synthetic strategies include formation of an S-Npyrroie bond in the early stages. A final cyclization step typically includes (i) intramolecular cyclization by creation of an N-X bond from a suitable pyrrole precursor or (ii) a 6 + 1 type cyclization that involves dielectrophilic species to form linker X and utilizes the nucleophilicity of the phenyl amino group and of the pyrrole ring at C2. Intramolecular processes with the formation... 

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