Fragmentation method, calculation

The actual 2/ system [34] lists 13 correction rules and 169 fragment values, including 14 new heterocyclic fragments as well as doubly and triply halogenated methyls. A typical calculation is depicted in Fig. 14.1 for quinidine. The 2/system is the only fragment method allowing manual log P calculation. Computerized... 

Fig. 14.1 LogP calculation for quinidine with the fragmental method according to Rekker and Mannhold. Calculation starts with the gross formula C20H24N2O2 definition of...

Considering the success of fragment methods, which apply additive models for log P predichon, one can assume that addihve approaches may also sahsfactory work for MLP. Indeed, similar to the Generalized Born model, one can consider fragments of molecules as centers of some potenhal functions and use an empirically defined distance function ) to calculate the MLP value by ... 

Abraham, D. J., Leo, A. J. Extension of the fragment method to calculate amino acid zwitterion and side chain partition coefficients. Proteins 1987, 2,130-152. 

HPLC-screening method calculated-PCKOC fragment method, Muller Kordel 1996) 3.40-5.33 3.80-5.40 (range, calculated from sequential desorption of 11 urban soils lit. range, Krauss... 

HPLC-screening method calculated-PCKOC fragment method, Muller Kordel 1996)... 

Pleiss, M.A. and Grunewald, G.L. An extension of the f-fragment method for the calculation of hydrophobic constants (Log F) of conformationally defined systems, / Merf Chem., 26(12) 1760-1764,1983. 

Methods based on molecular properties attempt to avoid the drawbacks of the fragmental methods, such as their failure to calculate log P for structures with missing fragments. However, in some cases, models were derived from sets of compounds with moderate chemical diversity limiting the accuracy of predicted log P. 

In an approach similar to that discussed above, Kthne et al. (1995) determined the fragmental solubility values of 58 structure fragments and melting points for the solubility (mty bf 694 compounds in water. Kthne compared the performance of different methods for the calculation of solubility in water, and showed that his fragmental method resulted in the smallest calculation error. 

Some researchers who use parameters derived from quantum chemical calculations on the whole solute molecule (Bodor, 1989) place their methods in a "theoretically-based" class. These are seen as preferable to methods which add the values assigned to structural parts, which then requires the assignment of interaction factors or corrections/ depending on how the parts are attached to each other. Fragment methods then are said to be in a purely empirical class and therefore obsolete. ... 

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