A multiway 3D QSAR analysis of a series of (S)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-6-methoxybenzamides

Recently, the multilinear PLS algorithm was presented by Bro and later implemented as a regression method in 3D QSAR by Nilsson et al. In the present article a well-known set of (S)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-6-methoxybenzamides, with affinity towards the dopamine D-2 receptor subtype, was utilised for the validation of the multilinear PLS method. After exhaustive conformational analyses on the ligands, the active analogue approach was employed to align them in their presumed pharmacologically active conformations, using (-)-piquindone as a template. Descriptors were then generated in the GRID program, and 40 calibration compounds and 18 test compounds were selected by means of a principal component analysis in the descriptor space. The final model was validated with different types of cross-validation experiments, e.g. leave one-our, leave-three-out and leave-five-out. The cross-validated Q(2) was 62% for all experiments, confirming the stability of the model. The prediction of the test set with a predicted Q(2) of 62% also established the predictive ability. Finally, the conformations and the alignment of the ligands in combination with multilinear PLS, obviously, played an important role for the success of our model.