Cascading libraries

However, SMV has a relatively low discriminating power, which may require the use of near-unity thresholds in order to distinguish very similar products. It can also result in ambiguous identification of batches of the same substance with different physical characteristics (e.g. samples of the same product with different grain sizes can have very similar correlation coefficients and may be confused) or different substances with high chemical similarity. In these cases, cascading libraries, as previously discussed, can be used. 

Some chiral compounds exhibit a different crystal structure for each pure enantiomer and their mixture the difference can be used to distinguish them. Again, the use of cascading libraries allows pure compounds to be distinguished from compounds contaminated with relatively small amounts of the other chiral forms. 

Keywords Absolute configuration, Amines, Amino acids, Carbenes, Cascade reactions, 2-chloro-2-cyclopropylideneacetates. Combinatorial libraries. Cycloadditions, Cyclobutenes, Cyclopropanes, Diels-Alder reactions. Heterocycles, Michael additions. Nitrones, Nucleophilic substitutions, Peptidomimetics, Palladium catalysis. Polycycles, Solid phase synthesis, Spiro compounds. Thiols... 

FIGURE 8.6 Corona discharge ionization cascade in positive (a) and negative (b) ion modes. (Reproduced from Raffaelli, A., Atmospheric pressure chemical ionization (APCI), in Cappiello, A. (ed), Advances in LC-MS Instrumentation, vol. 72 (Journal of Chromatography Library), Elsevier, Amsterdam, the Netherlands, 2007, 11-25. Copyright 2007. With permission from Elsevier.)... 

The items listed in the cascaded menu are the types of objects we can create using Capture as the front end. For this text, we are concerned only with the Project selection, which is used to draw schematics and simulate circuits, and the Library selection, which is used to create part libraries. Select Project to create a new project ... 

SeeDs-2 library was generated from their in-house database called rCat of 1,622,763 unique chemical compounds assembled from 23 suppliers (25). The filtering cascade began with MW (same as SeeDs-1), then the functional groups and solubility filters which resulted in 43 unique compounds (no overlap with SeeDs-1). These were then clustered by 2D, 3-point pharma-cophoric features to provide 3 clusters, and the centroids of each cluster was submitted for chemist review. Of the 395 selected compounds that were ordered, 357 passed QC to become the SeeDs-2 fragment library. 

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