Similarity of Structures

Table 1 contains a list of the dihexulose dianhydrides currently in the literature, together with some mixed fructose-glucose dianhydrides. Trivial and IUPAC names are included. Each entry has a proposed abbreviation. Because of the great similarity of structure between all the compounds in Table I, these abbreviations are used, rather than numbers, in the context of this chapter. Thus, 1 is named as ot-D-Fru/-l,2 2,1 - 3-D-Frup, 2 as (3-D-Fru/-l,2 2,3 - 3-D-Fru/, and 3 as 3-D-Frup-1,2 2,l -ot-L-Sor/>. 

Some of the polysaccharides constituting intermediate stages in the biosynthesis of heparin have been physically isolated.23 Their structure is strikingly similar to those of heparan sulfates,24 thus re-opening the often-raised question as to whether heparan sulfate indeed represents products of incomplete biosynthesis of heparin. A detailed account of the structure and biological properties of heparan sulfate is beyond the scope of this article. However, in view of similarities of structural fea-... 

Nevertheless, there is some similarity of structure between compounds (II) and (IV). It is known that with grem.-diethyl groups in the phosphorofluoridate molecule, e.g. di-(l-ethyl- -propyl) phosphorofluoridate (V), the toxicity is less than with <7em.-dimethyl groups (di-isopropyl phosphorofluoridate (IV)). We found that similarly tetraethylphosphorodiamidic fluoride... 

A kinetic model for single-phase polymerizations— that is, reactions where because of the similarity of structure the polymer grows as a solid-state solution in the monomer crystal without phase separation—has been proposed by Baughman [294] to explain the experimental behavior observed in the temperature- or light-induced polymerization of substimted diacetylenes R—C=C—C=C—R. The basic feature of the model is that the rate constant for nucleation is assumed to depend on the fraction of converted monomer x(f) and is not constant like it is assumed in the Avrami model discussed above. The rate of the solid-state polymerization is given by... 

A substituted quinolone structure is common to the group of quinolone antimicrobials, many of which are also fluorinated. There is sufficient similarity of structure as well as molecular shape to suggest that, with the appropriate antigen, a generic... 

Results The data in Table II offer the opportunity to compare phthalates of four different eight-carbon alcohols. The performance differences are perhaps greater than would be expected from such simple variations in skeletal makeup. The most notable differences are in volatility and low temperature properties, but other minor differences also exist. Greater linearity leads to increased efficiency (as measured by the 100% modulus), lower volatility, better flexibility at low temperatures, and better resistance to soapy water. In most circumstances, the linear alcohol phthalates are quite similar to straight chain phthalates. This is to be expected in view of the close similarity of structures. (The true value of a plasticizer system must, of course, consider not only oerformance but price. Thus, high efficiency can sometimes be a disadvantage when costs on a pound volume basis are calculated. In other words, a less efficient plasticizer often gives the lowest compound pound volume cost.)... 

The fluorescence of coumarin compounds has been well known since 1911, when it was observed that the absorption band of coumarin at 311 nm was bathochromically shifted by one of several auxochromic groups, such as hydroxyl or amino, in the 3- or 7-position. A comparison of the stilbene molecule (88) with 3-phenylcoumarin (93) indicates the similarity of structure, and basically similar substitution patterns in the latter molecule have produced similarly useful FBAs (69FRP1568007). 

A variety of spectroscopic studies of metal cupferronates have been carried out by a number of investigators. The IR spectra of Cu2+, Hg2+, Al3+, Fe3+, Ga3+, Bi3+, Ti4 Zr4+, V4 Th4+, U4+, V5+ and Nb4+ cupferronates indicate a close parallelism in the spectra of different metals in the same oxidation state, indicating similarity of structural features. The absorption maxima in the 930-400 cm-1 region move to the lower frequency side, as expected, with increasing atomic weight of the cations and these, therefore, apparently correspond to the vibrations of the metal-oxygen bonds.104... 

The second group involves polymers with three-dimensional ordering of side branches (e.g., those forming Mj-phaseXTable 5). On X-ray patterns of these polymers 3-4 narrow reflexes at wide angles are observed. As a rule, the authors define this type of structure as crystalline, or ascribe a smectic type of structure, characteristic for ordered smectics in SE or SH phases. The heats of transition from anisotropic state to isotropic melt are usually small and do not exceed the heats of transition smectic liquid crystal — isotropic melt . The similarity of structural parameters of three-dimensionally ordered smectics and that of crystalline polymers of the type here considered, make their correct identification quite a difficult task. 

The ECOSAR program is used to predict the aquatic toxicity of chemicals based on their similarity of structure to chemicals for which the aquatic toxicity has been previously measured. Since 1981, the USEPA has used (Q)SARs to predict the aquatic toxicity of all new industrial chemicals (Nabholz et al. 1993 Zeeman et al. 1995). The acute toxicity of a chemical to fish (both fresh- and saltwater), water fleas... 

Aquatic toxicity of chemicals based on their similarity of structure to chemicals for which the aquatic toxicity has been previously measured (see Table 19.3 for a list of endpoints)... 

Do more detailed similarities of structure and mechanism accompany the broad relationships of Branden s topological analysis [72] Functionally equivalent groups around the substrate are illustrated in Fig. 35 for lactate dehydrogenase, glyceralde-... 

The normal classification of material by oxidation state is inappropriate for nitrosyl complexes because the oxidation state concept is very much a formalism for them. Instead we shall use the generally accepted [M(NO)x] + classification in which x is the number of coordinated NO groups and n the number of metal d electrons, the latter being calculated on the basis that NO+ is the coordinated moiety. As will be apparent, osmium complexes within each such category do in fact show considerable similarities of structure and reactivity, and also with their ruthenium analogues. Osmium is unusual in forming an [M(NO)]5 type of complex. 

Based upon similarity of structure and activity, Pea-HGH-I and II are classified as members of the AKH/RPCH family of neuropeptides. 

The elucidation of the primary site and biochemical mode of action of inhibitors is often difficult and not necessarily associated with the mechanism of resistance in field isolates. Nevertheless, information on the mechanism of resistance can provide evidence to determine the site of action. Therefore, the classification of fungicides is based on crossresistance reactions rather than chemical similarities of structures or proposed modes of action (Table 1). Based on available information in the literature, three categories of inhibitor classes can be made Classes with known mode of action and known mechanism of resistance, classes with proposed mode of action and unknown mode of resistance but wide-spread field resistance, and classes in which resistance is claimed to occur in the field but both mode of action and resistance are not known. 

TS-2 was shown to be almost indistinguishable from TS-1, as predicted by similarity of structures and active sites [46]. Ti-Beta zeolites, with and without A1 in the structure, were less effective than TS-1. The yields based on hydrogen peroxide, just above 60%, were typical of rather modest catalysts. Apparently, product selectivity was influenced by the A1 content. The relatively hydrophilic Ti,Al- 3 produced catechol and hydroquinone in nearly equimolar amounts [50]. The Al-free Ti-p showed a higher catechol selectivity, with an ortho/para ratio of 2 [47]. In both cases, the greater spaciousness of pores favoured ortho hydroxylation. For a useful comparison, the orthojpara ratio on medium-pore TS-1 was 0.77 under analogous conditions. 

It is possible to arrange the war gases in the chronological order in which they were first used in the war of 1914-18. This is the order employed in Table XIV at the end of this book, where the physical, chemical and physiopathological properties of the principal war gases are summarised. In the text, however, it is considered more convenient to catalogue them according to chemical relationships and similarity of structure. 

Golub MA. Concerning apparent similarity of structures of fluoropolymer surfaces exposed to an argon plasma or argon ion beam. Langmuir 1996 12 3360-3361. 

Cholesterone, progesterone, and other eneones in the cholestane series have a highly sterically hindered tail position and afford only head-to-head pinacols at a mercury cathode in ethanolic buffers at both pH5 and pH 12.5 [142-144]. The stereochemistry of the pinacols formed from some cyclohexenones similar of structure to the steroids has been studied in some detail [145,146]. Dimerization of radicals derived from XXXVII is highly enantioselective. It occurs by reaction between radicals from the same enantiomeric configuration to give only one of the possible racemic pinacols XXXVIII. Where an angular methyl substituent is present as in XXXIX, the dimerization is less enantioselective. It is... 

Quantitative studies on structure-acti ily and structure-property relationships are powerful tools m directed drug research In recent years, various strategies have been developed to eharacieri/e and classil y structural patterns by means ol molecular descriptors. It became possible not only to assess diversities or similarities of structure databases, but molecular descriptors also facilitate the identification of potential bioactive molecules from the rapidly increasing number of compound libraries. They even allow for a controlled de-novo design of new lead structures. 

TABLE 3-2 Similarity of Structures to Oiethylstllbestrol (DES), Using Various Descriptors... 

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