Extension correlation

Conformational analysis has been used to find and predict conformations which maximize antibiotic activity, using x-ray crystal stmctures coupled with nmr and cd spectra. An early approach utilized the Dale diamond lattice conformational model (480), which was extended to other diamond lattice models (472,481—483). Other studies have reHed on nmr data (225,484—491). However, extensive correlations between conformation and biological activity have not been successful (486,492). 

Presented in Table 1 is a list of the parameters in Eqs. (2) and (3) and the type of target data used for their optimization. The infonnation in Table 1 is separated into categories associated with those parameters. It should be noted that separation into the different categories represents a simplification in practice there is extensive correlation between the different parameters, as discussed above for example, changes in bond parameters that affect the geometry may also have an influence on AGsoivation for a given model compound. These correlations require that parameter optimization protocols include iterative approaches, as will be discussed below. 

The most extensive correlation of ESR results for trimethylsilyl-substituted aromatic radical anions with Hiickel MO calculations to date is the work of Sipe and West (118, 119). The optimum heteroatom parameters for both the simple Hiickel treatment and the Hiickel-McLachlan treatment, using a Qm = 28 G, for Me3Si were as follows Hiickel, hsi = -2.00, kcS1 = 0.70 Hiickel-McLachlan, hsi = -1.80, kcsi = 0.70, X = 0.30 The values for Me3Ge were as follows Hiickel, hoe = -1.45, kCGe = 0.40 Hiickel-Me Lachlan, = -1.40, kCGe = 0.40 X =... 

Infrared vibrational energies of ligating groups such as CO, N2, NO or RNC (R = alkyl or aryl) have been extensively correlated with redox potential data.28 37""41 For a series of closely related mononuclear complexes it is generally observed that as E° (or EVl) for the oxidation of members of the series becomes increasingly positive, then v, the infrared stretching frequency for the (ter-... 

Extensive correlations for free convection between cylindrical, cubical, and spherical bodies and various enclosure geometries are given by Warrington and Powe [80]. The correlations cover a wide range of fluids. 

Thus we may consider that the more covalent the M—O bond tends to be, the more acidic are the hydrogen atoms in the aquated ion, but at present there is no extensive correlation of the acidities of aqua ions with properties of the metal. 

Changes in mineral surface morphologies have also been extensively correlated with silicate weathering. Dom (1995) used the digital processing of backscatter electron imagery to determine... 

Extensive correlation tables and discussions of characteristic group frequencies can be found in specialized references. As one example, consider the band patterns of toluene, and of o-, m-, and p-xylene, which appear in the frequency range 2000 to 1650 cm" (Fig. 2). These band patterns are due to changes in the dipole moment accompanying changes in vibrational modes of the aromatic ring and are surprisingly similar to those for monosubstituted and other o-, m-, and p-disubstituted benzenes. 

Extensive correlation card indexes are maintained in the OTS offices, and mail and phone inquiries will be answered from these files. 

Indeed, Raymond and co-workers have presented extensive correlations of the crystallographic data on the organolanthanide and... 

Clearly, the polyester stationary phases advocated earlier (79) in the field of lipid separations possess only a limited thermal stability. Cyanopropyl silicones [356,357] now provide selective and more stable stationary phases for the separation of FA esters. However, the column selectivity alone falls short of some resolution requirement, while capillary GC seems to be the most profitable route to pursue. The state-of-the-art separation of FA methyl esters is reflected in Fig. 3.21 [358], where many of the minor structural differences in the chromatographed FA molecules yield readily distinguishable peaks. Acquisition of suitable standards as well as extensive correlations of FA molecular parameters with retention characteristics [359] are now clearly needed. 

Herriott used the phosphorus epimers of 0-(-)-menthyl methylphenylphosphinoth-ioate to demonstrate the almost quantitative stereospecificity in the reaction with mCPBA by contrast, the use of trifluoroperoxyacetic acid was less successful, with a retention to inversion ratio of 21 79. A further feature in favour of mCPBA is the independence of its activity relative to solvent. Other extensive correlations were made by Inch and coworkers during investigations into the stereochemistry of displacement reactions at phosphorus in compounds based on a carbohydrate template 81 by means of structural assignments based on infrared absorption frequencies for the P=0 bond together with P NMR chemical shifts, they showed that mCPBA oxidation of thiophosphoryl or selenophosphoryl bonds (A or B = =S or =Se, B or A = Me or Ph) occurred highly stereoselectively with the formation of the phosphonate ester with retained stereochemistry ... 

Extensive correlations of IR absorption frequencies against functional groups, and substituents on phosphorus, have been made by Thomas and Corbridge for condensed phase spectra. 

For the theoretical determination of spectroscopic constants of weakly bound van der Waals molecules like Ru2, a highly accurate treatment for both electron correlation and relativity becomes necessary to obtain reliable results [123]. Size-extensive correlated relativistic calculations are desirable, but at present these straightforward approaches are computationally too demanding because of the large basis sets required including multiple polarization functions, suggesting that the RECP approximation is the method of choice. 

Attempts at correlation analysis for X—C—H acidity have been made for a long time. Bowden and colleaguesexamined the problem in 1970 for the pKa values of 9-X-fluorenes and related series. For a limited selection of substituents X in 9-X-fluorenes, a correlation with Taft s cr values for X was found. A more general correlation, albeit with considerable scatter, was found with AM, a parameter based on LCAO-MO calculations. 9-Cyanofluorene fitted the line quite well, but malononitrile deviated strongly. More extensive correlation with cr values was found for the effect of X in the series XCH(N02)2 but the substituents X did not include any of strong +R effect such as CN or NO2. 

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