Support-bound

For a local potential V(r) which supports bound states of angular momentum i and energy < 0, the phase shift linij Q (Ic)) tends in the lunit of zero collision energy to n. When the well becomes deep enough so as to introduce an additional bound level = 0 at zero energy, then linij ... 

This group was developed for terminal protection of an oligonucleotide sequence for purposes of monitoring the purification by HPLC after a synthesis. It shows characteristic UV maxima at 365 and 380 nm. The group is prepared from the chloride in pyridine and can be bound directly to the support-bound oligonucleotide. ... 

Unreacted support-bound nucleoside hydroxy groups can be blocked with diethoxy-triazolylphosphine. Oxidation of the phosphite triester to phosphate triester was achieved by I2. Yields in the condensation exceeded 95%. Tetrazolide as phosphitylating reagent is superior to a 4-nitroimidazolide, a triazolide, or even a chloride.11061... 

Support-bound reagents and scavengers have become increasingly popular in the preparation of compound libraries.1111 When polymer-supported... 

Reductive amination of an aldehyde with excess primary amine, using a support-bound borohy-dride, provides the desired secondary amine contaminated with the primary amine precursor. Covalent capture of the primary amine with a support-bound aldehyde provides the pure secondary amine. Treatment with excess isocyanate yields the final urea product, which is purified by reaction with a support-bound amine to remove unreacted isocyanate. For the full potential of this method to be realized, further development of support-bound reagents and scavengers for most of the important chemical transformations will be necessary. Al-... 

Scheme 5. A library of functionalized ureas synthesized using support-bound reagents and scavengers.

Nine different support-bound compounds are prepared with a single chemical structure on each resin bead... 

For the vast majority of drug discovery efforts compound libraries have been screened following cleavage from support. For other applications, support-bound libraries have been employed much more extensively.111... 

In one scenario, the first carbohydrate is anchored via its reducing end (see Scheme 2.1, case 1). Here the support-bound carbohydrate will function as an acceptor in the coupling step to a solution-based donor D. As the next cycle is contemplated, a unique acceptor hydroxyl must be exposed in the now elongated, resin-bound carbohydrate constmct. 

In addition to well-resolved one-dimensional (ID) 1H and 13C spectra, which are usually sufficient for monitoring synthetic steps, HR-MAS techniques can be applied to two-dimensional (2D) homonuclear and heteronuclear experiments, which allow a wealth of structural information to be obtained. H,13C HMQC (heteronuclear multiple quantum coherence) spectra are particularly useful in the analysis of solid support-bound oligosaccharides, since the anomeric protons exhibit characteristic resonances. Such a spectrum of a polymer-bound trisaccharide glycal is shown in Figure 8.4. 

DIRECT SOLID-PHASE GLYCOSYLATION OF SOLID-SUPPORT-BOUND PEPTIDES 273... 

MTBD = 7-methyl-l,5,7-triazabicyclo[4,4,0]dec-5-ene (23) is a strong base that allows the selective iV-methylation of o-n i tros uI I ony 1-substituted terminal amino groups of support-bound peptides (see Section 8.13).67-79... 

FIGURE 8.18 Methylation of the amino group of a support-bound peptide.92 The amino group is partially protected, methylated by a reagent that does not methylate peptide bonds and then deprotected.91 DMF = dimethylformamide. 

Enjalbal, C. Manx, D. Martinez, J. Combarieu, R. Aubagnac, J.-L. Mass Spectrometry and Combinatorial Chemistry New Approaches for Direct Support-Bound Compound Identification. Comb. Chem. High Throughput Screening 2001, 4,363-373. 

It has been reported by Patel and Gordon " that SPPS is limited by poor yields with hindered amines, deactivated aromatic aldehydes and slight over alkylation with aliphatic aldehydes. Johnson et al argued that because of the speed and convenience of automated SPPS, support-bound cyclization protocols are ideal for the preparation of numerous cyclo peptide analogues. 

Hessner, M.J., Wang, X., Khan, S., Meyer, L., Schlicht, M., Tackjes, J., Datta, M.W, Jacob, H.J., and Ghosh, S., Use of a three-color cDNA microarray platform to measure and control support-bound probe for improved data quality and reproducibility. Nucleic Acid Res., 31(11), 1-9, 2003b. 

Nevertheless, the direct nucleophilic displacement of support-bound carboxylates to prepare hydroxamates presents some limitations. For example, O-tert-butyldimethylsilyl-protected hydroxylamine displaces common acids from oxime resin however, further treatment with trifluoroacetic acid (TFA) is necessary to remove completely the silyl... 

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