Linker Ether

Whatever the chosen linker (ether, ester, amine,...) between both fragments, no improvement of the antimalarial activity was noted. It was therefore concluded that... 

Synthesis of the corresponding purine nucleoamino acids Fmoc-Ser " - and Fmoc-Ser " - via the O-MTM ether 3 was compromised by a lack of re-gioselectivity during the l2-raediated nucleosidation. The incorporation of these nucleoamino acids into aPNAs is also problematic because of facile acid-catalyzed depurination. The latter problem could be traced to the -CH2-O-CH2- linker [38]. We decided to circumvent the problem by synthesizing the isosteric norvalinyl... 

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. ... 

A second strategy is to attach a linker (also referred to as a handle or anchor) to the resin followed by assembly of the molecule. A linker is bifunctional spacer that serves to link the initial synthetic unit to the support in two discrete steps (Fig. 3). To attach a linker to a chloromethyl-PS resin, a phenol functionality such as handle 4 is used to form an ether bond (Fig. 4). To attach the same handle to an amino-functionalized support, acetoxy function 5 or a longer methylene spacer of the corresponding phenol is applied to form an amide bond. Both of these resins perform similarly and only differ in their initial starting resin [4], An alternative approach is to prepare a preformed handle in which the first building block is prederivatized to the linker and this moiety is attached to the resin. For peptide synthesis, this practice is common for the preparation of C-terminal peptide acids in order to reduce the amount of racemization of the a-carbon at the anchoring position [5],... 

Silyl-derived linker 36 was prepared in three steps from a silyl ether of serine and incorporated for Fmoc/tBu-based assembly of protected gly-copeptide blocks (Scheme 11) [42]. The a-carboxylic acid function of serine was protected as an allyl ester. Deprotection by a Pd(0) catalyst in the presence of dimedone liberated the carboxylic acid in order for subsequent... 

Nakamura K, Hanai N, Kanno M, Kobayashi A, Ohnishi Y, Ito Y, Nakahara Y. Design and synthesis of silyl ether-based linker for solid-phase synthesis of glycopeptides. Tetrahedron Lett 1999 40 515-518. 

Boehm TL, Showalter HDH. Development of a novel silyl ether linker for solid-phase organic synthesis. J Org Chem 1996 61 6498-6499. 

Figure 2.3 SAM surface modification has been done using monothiol and dithiol compounds containing PEG linkers. Useful coatings typically contain mainly PEG-hydroxyl or PEG-monomethyl ether linkers that provide a biocompatible lawn, which prevents nonspecific binding of proteins to the metallic surface. About 10 percent of the surface modifications are done using a longer carboxylate-containing thiol-PEG linker that provides sites for attachment of affinity ligands.

Recently, Miethchen modified diphosphinite 97 d with a crown-ether linker in the 1,4-positions in order to study the effect on enantioselectivity in Rh-cata-lyzed asymmetric hydrogenation reactions [99]. Introduction of the crown ether in the 1,4-position of the carbohydrate allows the enantioselectivity to be tuned, based on a strong effect of the formation of cryptate species with alkali ions. 

A soluble aminomethylated polyethylene glycol and a succinoyl linker were used to support a 9-fluorenylmethyl group for solution-phase glycosylation by the sulfoxide method. With the help of temporary protection by a 6-O-triphenylmethyl ether, the method could be carried out iteratively to form disaccharides (Scheme 4.69) [379],... 

To 100 MicroTubes in 100 mL of DCM, the following were added sequentially 4.96 g (9.2 mmol) Rink amide linker (note 6), 3.20mL (18.4mmol) DIEA, and6.9g (18.4mmol) HATU (note 7). The reaction mixture was shaken at room temperature for 48 h. After the supernatant was removed by aspiration, the MicroTubes were washed sequentially with DMF, MeOH, and DCM for three cycles. The MicroTubes were dried under vacuum for 5 h after a final washing with ethyl ether. 

These authors developed the use of a 4-alkyloxybenzyl ether-type linker attached to the Merrifield resin via an ester function that allowed the cleavage of the oligosaccharides under two different conditions. Using the reactivity of the activated... 

An interesting linker is based on bis(4-hydroxyphenyl)disulfide 3 (Scheme 9.9). Both MPEG and the carbohydrate are linked as ethers, and for removal from MPEG, the linker s disulfide bond is reductively split by propanedithiol. The carbohydrate is freed as a glycoside of 4-hydroxyphenylmercaptan.38... 

The galactosyl glycal 72 was bound to solid phase via a silyl ether linker. Epoxidation of the glycal using 2,2-dimethyldioxirane and subsequent electrophilic activation of the epoxide resulted in the glycosylation of 3,4-di-O-benzyl glucal 73. After acetylation of the product, the polymer-linked trisaccharide 74 was obtained. 

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