Conformation-Dependent Chirality Code

Tutorial Conformation-Independent and Conformation-Dependent Chirality Codes [34]... 

In most common chiral molecules, chirality arises from chiral tetravalent atoms. A conformation-independent chirality code (CICC) was developed that encodes the molecular chirality originating from a chiral tetravalent atom [42], For more generality, a conformation-dependent chirality code (CDCC) is used [43]. CDCC ti cats a molecule as a rigid set of points (atoms) linked by bonds, and it accounts for chirality generated by chirality centers, chirality axes, or chirality planes. 

The conformation-dependent chirality code constitutes a more general description of molecular chirality, which is formally comparable with the CICC [43], The main difference is that chiral carbon atoms arc now not explicitly considered, and combinations of any four atoms are now used, independently of the existence or nonexistence of chiial centers, and of their belonging or not belonging to ligands of chiral centers. 

The two values, e and c, calculated for all combinations of four atoms, are then combined to generate a conformation-dependent chirality code. fc )QO using Eq. (30), where n is the number of atoms in each molecule, and r introduces the conformation dependence ... 

The number of discrete values of/cocc(i ) determines the resolution of the chirality code. Again, is a smoothing factor. An example with the conformation-dependent chirality codes for the enantiomers of 4 in two different conformations is shown in Eigurc 8-1 f. 

Therefore the 28 analytes and their enantiomers were encoded by the conformation-dependent chirality code (CDCC) and submitted to a Kohoiien neural network (Figure 8-1 3). They were divided into a test set of six compounds that were chosen to cover a variety of skeletons and were not used for the training. That left a training set containing the remaining 50 compounds. 

Moreover, the Conformational-Dependent Chirality Code (/cdcc) was defined to account for conformational behavior of molecules, replacing the chirality signal Syki by a conformational-dependent geometric parameter Qjia [Caetano, Aires-de-Sousa et al., 2005]. The occ code is calculated as... 

Conformational-Dependent Chirality Code chirality descriptors (0 Chirality Codes) conformational global sensitivity molecular descriptors (0 invariance properties of... 

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