Novel chirality descriptors derived from molecular topology

Several series of novel chirality descriptors of chemical organic molecules have been introduced. The descriptors have been developed on the basis of conventional topological descriptors of molecular graphs. They include modi fied molecular connectivity indices, Zagreb group indices, extended connect ivity, overall connectivity, and topological charge indices. These modified descriptors make use of an additional term called chirality correction, wh ich is added to the vertex degrees of asymmetric atoms in a molecular graph . Chirality descriptors can be real or complex numbers. Advantages and draw backs of different series of chirality descriptors are discussed. These des criptors circumvent the inability of conventional topological indices to di stinguish chiral or enantiomeric isomers, which so far has: been the major drawback of 2D descriptors as compared to true 3D descriptors (e.g., shape, molecular fields) of molecular structure. These novel chirality descriptor s have been implemented in a quantitative structure-activity releationship (QSAR) study of a set of ecdysteroids with a high content of chiral and ena ntiomeric compounds using the k nearest neighbor QSAR method (kNN) recently developed in this laboratory. We show that the results of this study compa re favorably with those obtained with the comparative molecular field analy sis (CoMFA) applied to the same dataset. The novel chirality descriptors of molecular structure should find their applications in QSAR studies and rel ated investigations of molecular sdatasets.