Identical parent components

In early work no such NMR chemical shift changes relative to those of the parent components were observed for polypseudorotaxanes with aliphatic backbones and aliphatic crown ethers as the cyclic species [108, 109]. Model studies were performed with 18-crown-6 (18C6), which is so small that it cannot be threaded. The recovery of intact 18C6 under conditions identical with those for the syntheses of the polyrotaxanes ruled out the possibility of side reactions. The effective removal of the small crown ether by precipitation into a solvent which was poor for backbone but good for the cyclic demonstrated the effectiveness of the purification procedure. In addition, reaching a constant min value after multiple precipitations and the absence of the peak for free crown ether in GPC traces indicated that the larger crown ethers detected by NMR in the purified polymeric products were indeed threaded rather than simply mixed. 

Multiplying prefixes are used in the same way as with parent structures the series di, tri, tetra... for sets of identical substituents, the series bis, tris,tetrakis... for identically substituted identical substituents (or if linguistically better suited), and the series bi, ter, quater... for identical partial components directly joined together. 

As has already been conveyed in the discussions relating to parent structures, specific naming rules (on whose necessity opinions are divided) are to be obeyed for compounds assembled from identical cyclic components. The same holds for assemblies of identically substituted subunits, of... 

Figure 11,8 Composite decay curves for (A) mixtures of independently decaying species, (B) transient equilibrium, (C) secular equilibrium, and (D) nonequilibrium, a composite decay curve b decay curve of longer-lived component (A) and parent radio nuclide (B, C, D) c decay curve of short-lived radionuclide (A) and daughter radionuclide (B, C, D) d daughter radioativity in a pure parent fraction (B, C, D) e total daughter radioactivity in a parent-plus-daughter fraction (B). In all cases, the detection coefficients of the various species are assumed to be identical. From Nuclear and Radiochemistry, G. Friedlander and J. W. Kennedy, Copyright 1956 by John Wiley and Sons. Reprinted by permission of John Wiley and Sons Ltd.

Each of the scaffolds reported in Scheme 24 can be used for the production of a stereo-isomeric sublibrary based on the appropriate peptide sequence. For example, with the sequence A-B-C-D-E and scaffold (1) two types of stereoisomeric sublibraries can be prepared. One type includes the sublibraries A and B of Scheme 26 in which within a given sequence the configuration of each residue is successively inverted thus, retaining the identical connectivity as in the parent linear peptide. In the second type 265 of sublibraries C and D (Scheme 26) the direction of the amide bond is inverted and hence the connectivity is not maintained. In most members of these sublibraries the overall conformation of the scaffold is maintained and therefore these components constitute stereoisomeric sublibraries of the parent library. Conversely, by introducing amide bond surrogates such as reduced amide bonds1465 or thioamide bonds 260,466 the conformation of the scaffolds are changed and their conformational flexibility enhanced. 

For the cycloscan, conformational libraries are synthesized by cyclization of continuous or noncontinuous bioactive epitopes and not by their insertion into a scaffold. Originally, the concept of cycloscan was introduced for the generation of backbone-cyclized peptide libraries 467 however, cycloscan can also be applied to other modes of cyclization. In this approach all components of each sublibrary bear the identical sequence, and differ from each other in distinct parameters that affect their conformation, but do not alter their connectivity, and hence their potential bioactivity. This is achieved by gradually introducing discrete conformational perturbations, which allow an efficient screening of the conformational space of the parent peptide. The majority of the components of such libraries should be inactive, because they do not overlap the bioactive conformation. However, the peptide that does fit the bioactive conformation should be very potent and have all the pharmacological advantages of cyclic peptides. 

In the absence of information as to the identity of the impurities or minor components associated with the parent substance, or of the identity of parent substance as well as the impurities, it appears that the freezing point is the only property which may be utilized to give a quantitative estimate of the purity. 

Confirmation of the identity of the gas chromatographic components has been accomplished by thin layer chromatography, relative retention times on different gas chromatographic columns, "p" values, and most recently by mass spectrometry. Dicofol can be separated from its phenone by using a Florisil column (17) or TLC. Dehydrochlorination of dicofol to DBP can be used as a confirmatory test for the parent compound. Gajan and Lisk (23) used cathode ray polarography to analyze vegetables for dicofol residues. 

Immediately on entering the body, a chemical begins changing location, concentration, or chemical identity. It may be transported independently by several components of the circulatory system, absorbed by various tissues, or stored the chemical may effect an action, be detoxified, or be activated the parent compound or its metabo-lite(s) may react with body constituents, be stored, or be eliminated—to name some of the more important actions. Each of these processes may be described by rate constants similar to those described earlier in our discussion of first-order rate processes that are associated with toxicant absorption, distribution, and elimination and occur... 

In some cases, single component representation is unsuitable. Figure 14.4 shows a simple sequence of structure standardization executed by a compound registration system including structure correction of the benzothiadiazole, salt/addend stripping and neutralization to depict the canonical parent structure representation. Any alternative salt form or structure representation of this compound will be standardized into the same parent structure and thus recognized as identical (at that level). 

Other complications that arise are (a) that the surface compositions of glassy metals to be used as electrocatalysts are rarely identical with the corresponding bulk compositions, as was shown in recent Auger surface analysis experiments by Vracar and Conway (134), and (b) that when such alloys are used as anodes for O2 evolution in water electrolysis an oxide film of appreciable thickness is formed, and the distribution of elements of the alloy in the film is not usually the same as in the parent metal owing to some preferential anodic leaching of any base-metal components that are present in the alloy. 

Synthesis control has two tasks directly associated with it. These are to identify or verify the identity of a combinatorial component and to determine the purity of the synthetic product. When characterizing a parallel library it is a relatively easy task to obtain a molecular weight from a small amount (femto-mole) of compound and thereby obtain a crude identification of the product. This circumvents the need to perform more difficult NMR or IR spectral interpretation and sample introduction maybe performed by a simple flow-injection atmospheric pressure ionization (API)/MS system. Purity assessment is typically based on area percentage normalization of the total ion chromatogram, assuming equivalent ionization of impurities and parent compounds, or a secondary detector, such as UY... 

Recently Prota and co-workers (789) have succeeded in isolating a melanochrome using an improved procedure that involves metal-catalyzed oxidation of DI at pH 7. Dithionite reduction followed by acetylation with acetic anhydride produced a mixture of leucome-lanochrome acetate oligomers, with the symmetrical 2,2 -dimer, 7, as the major component. Mild alkaline hydrolysis under anaerobic conditions gave the parent compound 8, which underwent rapid autooxidation to a blue-purple pigment with a chromophore identical to that of the oxidation product of DI, This process suggests that the Dl-derived melanochrome is a quinone derived from 8. 

The name sialic acid" has been given to the several nonulosaminic acids isolated from the submaxillary mucoproteins, although the chemical composition of these varies with the species source. Svennerholm has proposed that the name sialic acid be restricted to the basic structure common to all these various sialic acids thus ovine sialic acid" would be designated Af-acetylsialic acid. However since this basal component, here termed sialic acid, is identical with neuraminic acid, it would seem more appropriate to adopt the name neuraminic acid for the parent add and to retain the name sialic acid to denote the various mono- and di-acyl neuraminic acids of natural occurrence in mucoproteins, regardless of their source. This is the convention which has been used in referring to the various nonulosaminic acids in Table I and thoughout this article. ... 

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