Libraries preparation

The amino acid sequence of the human erythrocyte glucose transporter was deduced from the nucleotide sequence of a cDNA clone in 1985 [106]. Polyclonal antibodies raised against the protein were used to screen a Xgtl I cDNA library prepared from the human hepatocellular carcinoma cell line HepG2. (Like many other transformed... 

Figure 1. General schematic of a combinatorial library prepared from a small set of building blocks.

The preparation of a combinatorial library requires the simultaneous manipulation and isolation of many different compounds. A uniform sequence of operations is required to efficiently prepare and isolate each member of the library. In contrast the traditional synthesis of compounds utilizes conditions tailored specifically to the compound desired. A key challenge for library preparation is the development of a robust synthesis sequence that cleanly incorporates chemical building blocks containing a diverse range of chemical functionality in high yields. Equally important are the development of uniform and efficient methods to isolate intermediates and products from solvents, reagents, and byproducts. 

Scheme 1. Atriazine library prepared by solution phase synthesis.

In this review we have chosen to focus on strategies for designing the templates and scaffolds used in library synthesis. Equally important is the selection of building blocks for library preparation. A number of powerful computational methods have been developed to select the minimal set of building blocks that maxi-... 

Oxazolidinone familes, synthesis of, 7 7 741 Oxazolidinone libraries, preparation of, 77 742... 

On the basis of the early results described above, random glycosylation as an approach to oligosaccharide library preparation has been further pursued. The product distributions in these early reactions were difficult to determine, and in subsequent work, the aglycon of the acceptor was changed to the p-methoxyphenoxy octyl... 

Rivero IA, Gonzalez T, Pina-Luis G et al (2005) Library preparation of derivatives of 1,4, 10,13-tetraoxa-7,16-diaza-cycloctadecane and their fluorescence behavior for signaling purposes. J Comb Chem 7 46-53... 

Particularly noteworthy examples are Entries 8 and 9 in Table 3.19 these represent a diastereoselective RCM in which the stereoselectivity is controlled by the catalyst [886]. Entries 17, 23 and 24 (Table 3.19) illustrate the use of RCM for the solid-phase synthesis of lactams [894]. RCM induces both ring closure to the lactam and cleavage from the support. Although elegant at first glance, the usefulness of this methodology will be limited if the products must be used without further purification (as is usually the case for compound libraries prepared by parallel synthesis). Because relatively large amounts of catalyst are required, the crude products will only be acceptable for assays in which transition metal complexes do not interfere. 

In the 1970s and 1980s, however, it was believed that the key to wider use of solid-phase supported reagents and catalysts is their adoption in industry for fine chemical and pharmaceutical manufacturing on a large scale. In fact, this restricted view hampered their wide use [7]. The dramatic developments in the need for compound library preparation in pharmaceutical and agrochemical industries have finally removed functionalized supports from their academic corner and helped reinvent them for industrial purposes and applications. 

Selection-independent analysis In this case, library analysis occurs strictly after and apart from the library selection experiment. Typically, what this means is that the solution resulting from a library is analyzed by HPLC or HPLC-mass spectrometry (HPLC-MS), and compared with the chromatographic trace obtained for an identical library prepared in the absence of target. This provides an internal control for self-selection processes and (hopefully) allows direct identification library members undergoing enhancement through visual inspection. If selfselection is the goal, one simply compares HPLC traces of libraries at different time points. 

In the screening of genomic libraries prepared from environmental samples collected in various parts of the world, more than 200 new nitrilases were discovered that allow mild and selective hydrolysis of nitriles (150). One of them catalyzes the (J )-selective hydrolysis of 35 with an ee value of 94.5% at a substrate concentration of 100 mM (46). However, when experiments were done at a more practical concentration of 2.25 M, activity and enantioselectivity suffered (ee only 87.8%). 

More specific libraries, such as polymer thin film (gradient) libraries or libraries prepared via controlled polymerization techniques, are not part of this overview, but will be discussed in detail in other chapters of this book [94, 95],... 

Solid phase attachment of histidine-containing peptides by anchoring the imidazole ring to trityl resins has been developed for combinatorial library preparation of diketopiperazines <99TL809>. Histidine, histamine, and urocanic acid are edl imidazole-containing molecules that have been attached to a trityl-type resin to allow their application to combinatorial chemistry <99TL2825>. 

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