Development Of Highly Selective Topological Indexes Of Compounds And Their Uniqueness Test

EAID, approached by Professor Lu Xu, is a highly discriminating topological index. A total of over 14 million structures were used to examine the uniqueness of EAID herein, no degeneration was found. In this thesis the definition of degeneration is: if two different graphic structures were represented by the same value of a topological index, that is, the two chemical structures can't be distinguished by the topological index, they are called ‘degeneration'. These structures mentioned-above include more than 3.8 million acyclic alkanes with 1-22 carbon atoms; more than 380 thousand compounds with heteroatoms; more than4 million benzenoids composed of 1-13 benzene rings; and three real databases(NCI, Pubchem, STocks)containing more than 5.9 million molecules. However, when larger databases were used to evaluate the uniqueness of EAID index, duplicates occurred. For acyclic alkanes with 23 and 24 carbon atoms, 5 and 13 degenerates out of more than 20 million compounds were found; for the ZINC real database of more than20 million structures, 10 degenerates were searched. It indicates that EAID is still not perfect for uniquely representing graphic structures, that is, the index should be improved.In order to increase discriminating power of EAID, 2-EAID was suggested on the basis of EAID. The databases composed of more than 55 million compounds as mentioned above were used to test the uniqueness of 2-EAID. The results indicate that just 2 duplicates occurred from the ZINC database and the other databases can be uniquely distinguished. Obviously, the discriminating power of 2-EAID is significantly higher than EAID.An attempt was made to investigate if the combination of EAID index and other index can improve the discriminating power. In particular, Wiener index was introduced into EAID index, and the new suggested topological index is called 3-EAID. The uniqueness test of 3-EAID was performed by all the structures tested for 2-EAID and two more databases as follows:(1) more than 36 million acyclic alkanes with 25 carbon atoms;(2) more than 15 million benzenoids composed of 14 benzene rings. The results indicate that 3-EAID index uniquely distinguishes all the real databases and virtual databases containing more than 107 million compounds. By contrast, the results of uniqueness test of EAID index for databases(1) and(2) are 75 and 29 pairs of duplicates, individually; and those of 2-EAID index for databases(1) and(2) are 15 and 1 pairs of duplicates, individually.The virtual databases in this thesis were obtained from in-house program, among them acyclic alkanes and structures with heteroatoms were enumerated by structure generator in our laboratory and the benzenoids were enumerated by a program in our published methods. The real databases were freely downloaded from internet.In summary, in our knowledge from literatures to date acyclic alkanes with 23-25 carbon atoms are firstly enumerated and 3-EAID index is the top discriminating topological index. In June 2015, the registered organic and inorganic substances in the world largest chemical database sponsored by chemical abstracts service were less than one hundred million. Therefore, 3-EAID index has potential to be used to uniquely represent structures in practical application, such as the management of large compound database,evaluation of organic compound structure, computer-aided drug synthesis.