Cleavage of linkers

There have been a few reports of enzymatic cleavage of linkers for carboxylic acids from PEG-grafted polystyrene supports, such as Tentagel (Table 3.8). Some of these linkers are also sensitive towards acids or bases, and will, therefore, only remain uncleaved under a narrow range of reaction conditions. 

A vast array of different methods and reagents are suitable for cleavage of linkers. Such cleavage is usually conducted with acids. The most popular cleaving reagent is therefore trifluoroacetic acid in a variety of solvents and at different concen-... 

The mild, neutral electron-transfer conditions associated with the use of Sml2 make the reagent ideal for the selective cleavage of linkers in solid-phase organic synthesis and other types of phase tag-assisted synthesis. 

The library was linked to the solid support via the photo-labile linker (see Fig. 8.6) which was cleaved at the 337 nm of the nitrogen laser used in MALDI-TOF mass spectrometers (optimal wavelength for cleavage of linker is 365 nm).The linker facilitated the... 

There is a large range of resins available for SPOS. These resins are derivatised polymer supports with a range of linkers. The roles of linkers are (i) to provide point(s) of attachment for the tethered molecule, akin to a solid supported protecting group(s), (ii) to provide distance from the polymeric backbone in order to minimise interactions with the backbone, (iii) to enable cleavage of product molecules under conditions compatible with the stability of the molecules and the reaction conditions employed for chemical transformations. Hence in order to... 

Application of the Knorr pyrazole synthesis has also been demonstrated on solid support. ° To prepare trisubstituted pyrazoles, the diketone was linked to the solid support to make 57 using a linker with an amide bond. Alkylation of the diketone followed by condensation of the hydrazine with the resulting diketone gave the desired pyrazoles as mixtures of isomers. Subsequent cleavage of the amide bond linker then provided the pyrazole amides 59. ... 

The conserved linker between repeats III and IV is critical for fast inactivation. Cleavage of the III-IV linkage causes a strong reduction in the rate of inactivation. A cluster of three hydrophobic residues (IFM) in the linker is an essential component, probably serving as a hydrophobic latch to stabilize the inactivated state. Other parts of the a subunit are also involved in fast inactivation. Conformational changes in the P region contribute to the slow inactivation process. 

Cleavage of all the linkers described above provide a functional group (carboxylic acid, amide, amine, etc) at the anchoring position. Silyl-based handles 71,72, and 73 as well as germanium-based handle 74 insert a C-H bond at the anchoring position and are referred to as traceless (Fig. 15) [82-... 

Fig. 1 Bioresponsive polyplexes. (a) Systemic circulation of shielded polyplexes in blood stream and attachment to cell surface receptor (b) endocytosis into endosomes, deshielding by cleavage of PEG linkers and activation of membrane-destabilizing component by acidic pH or other means (c) endosomal escape into cytosol (d) siRNA transfer to form a cytosolic RNA-induced silencing complex complex (e) cytosolic migration and intranuclear import of pDNA (/) presentation of pDNA in accessible form to the transcription machinery...

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