Solid-phase synthesis reproducibility

Fig. 10. A Comparison between the methodologies of solid phase synthesis and fluorous synthesis. (Reproduced by permission from J. Org. Chem., 36 (1998) 2917).

The principal difference between the synthesis of individual peptides and peptide libraries is that mixtures of amino acids, rather than individual amino acids, are incorporated into selected or all positions of the sequence of peptide libraries. However, all current peptide chemistry strategies can be used for the synthesis of peptide libraries. In general, library synthesis requires greater emphasis on simplicity and reproducibility of the synthesis process. Although soluble supports have also been used for peptide library synthesis,the majority of methods used to synthesize peptide combinatorial libraries utilize Merrifield s concept of solid-phase synthesis,which is based on the sequential assembly of peptides after covalent attachment of the C-terminal amino acid to a polymeric solid support. This enables the excess of reagents to be removed by simple wash and filtration processes, and avoids the... 

Fig. 14.4 Principle of redox-catalyst-mediated electro-organic synthesis on a solid phase.31 Reproduced by permission of the author and Wiley-VCH Verlag GmbH Co KGaA)...

Figure 16.1. Solid-phase synthesis of 1,2,3,4-tetrahydro-p-carbolines. (Reproduced from 26].)...

Figure 3.25 Solid-phase synthesis of aromatic oligoamides. Source Reproduced with permission from Santiago-Garcia JL, Aguilar-Vega M. Ear Polym J 2009 45 3210 [79]. Copyright 2009 Elsevier Ltd.

Figure 14.3. Solid-phase synthesis of C-terminal fluorescein-labeled peptides. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission from Ref. 22.

Figure 14.8. Solid-phase synthesis of unsymmetrical functionalized cyanine dyes with diverse fluorescent properties. Reproduced by permission of The Royal Society of Chemistry. Ref 43.

Figure 14.10. Solid-phase synthesis of fluorescent libraries based on (a) benzimidazolium and (b) quinaldinium scaffolds. Reproduced with permission from Refs 48, 50. Copyright 2006-2008 American Chemical Society.

Figure 3.1 General overview of solid-phase synthesis of sequence-defined glycopolymer segments a) suitable building blocks are synthesised, presenting a spacer unit or a functional moiety in the side chain b) these building blocks are then coupled in the solid phase until the desired chain length and sequence are obtained and c) on-resin modification of the side-chain functionalities introduces sugar ligands. The sequence-defined, monodisperse products are obtained after cleavage from the solid support. Reproduced with permission from D. Ponader,...

Since 1986, when the very first reports on the use of microwave heating to chemical transformations appeared [147,148], microwave-assisted synthesis has been shown to accelerate most solution-phase chemical reactions [24-27,32,35]. The first application of microwave irradiation for the acceleration of reaction rate of a substrate attached to a solid support (SPPS) was performed in 1992 [36]. Despite the promising results, microwave-assisted soHd-phase synthesis was not pursued following its initial appearance, most probably as a result of the lack of suitable instriunentation. Reproducing reaction conditions was nearly impossible because of the differences between domestic microwave ovens and the difficulties associated with temperature measurement. The technique became a Sleeping Beauty interest awoke almost a decade later with the publication of several microwave-assisted SPOS protocols [37,38,73,139,144]. There has been an extensive... 

A simple predecessor of the CEM setup for microwave-mediated SPOS was employed by Murray and Gellman in their synthesis of 14-hehcal 6-peptides [42], A 4 mL polypropylene solid-phase extraction tube was inserted into a 10 mL CEM vessel, allowing for both microwave heating and simple resin manipulation (Eig. 11). While using this setup gave reproducible results for their experiments, a discrepancy between the reactions target (set) temperatures and the actual temperatures was observed. Therefore, use... 

Other microwave-assisted parallel processes, for example those involving solid-phase organic synthesis, are discussed in Section 7.1. In the majority of the cases described so far, domestic multimode microwave ovens were used as heating devices, without utilizing specialized reactor equipment. Since reactions in household multimode ovens are notoriously difficult to reproduce due to the lack of temperature and pressure control, pulsed irradiation, uneven electromagnetic field distribution, and the unpredictable formation of hotspots (Section 3.2), in most contemporary published methods dedicated commercially available multimode reactor systems for parallel processing are used. These multivessel rotor systems are described in detail in Section 3.4. 

Zeolite formation depends on reaction conditions 2-4). It is generally believed that most zeolites are formed as metastable phases. According to Barrer (3), the course of the synthesis, beginning with the type of starting material, determines the structure of the zeolite formed. The studies of Zhdanov 2, 5) on the composition of liquid and solid phases of hydrogels indicate that the kind and composition of the zeolite formed depend on the hydrogel composition and that the results of crystallization of aluminosilicate gels obtained in the same way are reproducible. 

Figure 1.19 Mass spectra of acetaldehyde PFB-oxime (a), diacetyl mono PFB-oxime (b), acetoin PFB-oxime derivative (c), and o-chlorobenzaldehyde PFB-oxime (d) recorded in the GC/MS analysis of standard solution performed in positive ion chemical ionization mode using methane as reagent gas (reagent gas flow 1 mL/min ion source temperature 200 °C). Flamini et al., (2005) Monitoring of the principal carbonyl compounds involved in malolactic fermentation of wine by synthesis of 0-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine derivatives and solid-phase-microextraction positive-ion-chemical-ionization mass spectrometry analysis, Journal of Mass Spectrometry, 40, p. 1561. Copyright John Wiley Sons, Ltd. Reproduced with permission...

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