Similarity approach to QSAR. Application to antimycobacterial benzoxazines

The antimycobacterial activity in six series of substituted 3-phenyl-2H-benzoxazine-2,4(3H)-dithiones and 3-(phenyl)-4-thioxo-2H-benzoxazine-2,4(3H)-diones has been studied using a quantum molecular similarity approach. The approach is based on the use of fragment self-similarity measures as new universal molecular descriptors applicable for the design of novel theoretical QSAR models. Using this approach it was possible to show that while traditional QSAR models were able to describe the activity only within each of the six sets of studied molecules individually, the proposed approach is much more general and a single universal QSAR model describing the activity of all the 39 studied molecules in all the studied series together was built. The replacement of the oxo group by the thioxo group in position 4 on the benzoxazine ring of the antitubercular 3-(phenyl)-2H-benzoxazine-2,4(3H)-diones increases the activity, as well as the similar replacement in position 2.