Similarity-based

Hodgkin E E and W G Richards 1987. Molecular Similarity Based on Electrostatic Potential and Electri Field. International Journal of Quantum Chemistry. Quantum Biology Symposia 14 105-110. 

J. R. Whiteley andj. F. Davis, "QuaHtative Interpretation of Sensor Patterns using a Similarity-Based Approach," paper presented at the IFAC Symposium on On-Eine Fault Detection and Supervision in the Chemical Process Industries, Newark, Del., Apr. 1992. 

The base-promoted ring contraction of 3-bromo-2-pyrones to 2-furoic acids cf. Scheme llOd) is a well exemplified reaction 01CB1992,69JCS(C)1950,73JCS(P1)1130> which has also been applied to the obtention of benzofuran-2-carboxylic acids frorn 3-bromocoumarins 08CB830,70KGS(S2)166), Similar base treatment of 3-amino-2-pyrones provides pyrrole-2-carboxylic acids (Scheme IlOe) 75JHC129). 

One of the more important approaches to 1-azirines involves a similar base-induced cycloelimination reaction of a suitably functionalized ketone derivative (route c. Scheme 1). This reaction is analogous to route (b) (Scheme 1) used for the synthesis of aziridines wherein displacement of the leaving group at nitrogen is initiated by a -carbanionic center. An example of this cycloelimination involves the Neber rearrangement of oxime tosylate esters (357 X = OTs) to 1-azirines and subsequently to a-aminoketones (358) (71AHC-(13)45). The reaction has been demonstrated to be configurationally indiscriminate both syn and anti ketoxime tosylate esters afforded the same product mixture of a-aminoketones... 

In a similar base-catalyzed eyclization, Smrt et obtained a high yield of the pyrrolidone (21) from a y-halogeno-a-aminobutyro-hydroxamie acid and were unable to isolate any of the six-membered ring compound (22). 

Fortunately, there are other radioactive elements in nature that give similar bases for estimates. As a second example, potassium in nature... 

The activation of silylene complexes is induced both photochemically or by addition of a base, e.g. pyridine. A similar base-induced cleavage is known from the chemistry of carbene complexes however, in this case the carbenes so formed dimerize to give alkenes. Finally, a silylene cleavage can also be achieved thermally. Melting of the compounds 4-7 in high vacuum yields the dimeric complexes 48-51 with loss of HMPA. The dimers, on the other hand, can be transformed into polysilanes and iron carbonyl clusters above 120 °C. In all cases, the resulting polymers have been identified by spectroscopic methods. 

The parameter Ho reflects the ability of the solvent system to donate protons, but it can be applied only to acidic solutions of high dielectric constant, mostly mixtures of water with acids such as nitric, sulfuric, perchloric, and so on. It is apparent that the Ho treatment is valid only when/i //hi+ is independent of the nature of the base (the indicator). Since this is so only when the bases are structurally similar, the treatment is limited. Even when similar bases are compared, many deviations are found. Other acidity scales have been set up, among them // for bases with a... 

Terminal alkynes can be coupled by heating with stoichiometric amounts of cupric salts in pyridine or a similar base. This reaction, which produces symmetrical diynes... 

In ToUens reaction, an aldehyde or ketone containing an a hydrogen is treated with formaldehyde in the presence of Ca(OH)2 or a similar base. The first step is a mixed aldol reaction (16-38). 

Lajiness MS. Molecular similarity-based methods for selecting compounds for screening. In Rouvray DH, editor, Computational chemical graph theory. New York Nova Science Publishers, 1990 299-316. 

Historically, ligand structure-based design has been the most widely used approach to the design of target-directed chemical libraries. Methods that start from hits or leads are among the most diverse, ranging from 2D substructure search and similarity-based techniques to analysis of 3D pharmacophores and molecular interaction fields (Fig. 15.2). 

Willet P. Similarity-based approaches to virtual screening. Biochem Soc Trans 2003 31 603-6. 

If, after applying lead-Hke criteria (property and chemical filters), there are still too many compounds left one can use diversity/similarity-based techniques to select the final set For the example above, 64% of the starting compounds survive the compound acquisition process (around 64000 compounds in 11000 clusters), see Fig. 17.8. 

Hence there are multiple solutions for the final set of 10000 compounds. The final selection can be diversity driven using for example cluster analysis based on multiple fingerprints [63], hole filling strategies by using scaffold/ring analysis (LeadScope [66], SARVision [66]) or pharmacophore analysis [67, 68]. For a review of computational approaches to diversity and similarity-based selections, see the paper of Mason and Hermsmeier [69] and the references therein. 

Analytical methods for parent chloroacetanilide herbicides in soil typically involve extraction of the soil with solvent, followed by solid-phase extraction (SPE), and analysis by gas chromatography/electron capture detection (GC/ECD) or gas chromatog-raphy/mass spectrometry (GC/MS). Analytical methods for parent chloroacetanilides in water are similarly based on extraction followed by GC with various detection techniques. Many of the water methods, such as the Environmental Protection Agency (EPA) official methods, are multi-residue methods that include other compound classes in addition to chloroacetanilides. While liquid-liquid partitioning was used initially to extract acetanilides from water samples, SPE using... 

Lipoxygenase AnalytiCon Discovery db, Similarity based on 2D CATS descriptors 18 hits/430 tested [68]... 

Local methods, on the other hand, are characterized by input transformations that are approached using partition methods for cluster seeking. The overall thrust is to analyze input data and identify clusters of the data that have characteristics that are similar based on some criterion. The objective is to develop a description of these clusters so that plant behaviors can be compared and/or data can be interpreted. 

Whiteley, J. R.. and Davis, J. F., A similarity-based approach to interpretation of sensor data using adaptive resonance theory. Comput. Chem. Eng. 18(7), 637-661 (1994). 

Similarly, bases made from the metals of Group I on the periodic table, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), are called monobasic because they release one hydroxide ion into solution. Bases made up of Group II metals, such as calcium hydroxide [Ca(OH)2] or magnesium hydroxide [Mg(OH)2], release two hydroxide ions and are therefore dibasic. Like acids, any base that is capable of releasing more than one hydroxide ion into solution is called polybasic. 

We will also attempt to link everyday experiences with fiber and film production to the industrial engineering measures taken to improve polymer quality. The similarities based on non-textbook knowledge are thus emphasized. In-depth considerations regarding special technologies would be beyond the scope of this present chapter. Therefore, the main focus is to present a modern state of knowledge regarding the relationship of polymer quality and the requirements of the processes. 

It should be recognized that already Togni and co-workers had observed a similar base effect in the context of the intramolecular hydroamination of 2-... 

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