Molecular properties of the WB4101 enantiomers and of its chiral methyl derivatives for alpha 1-adrenoceptor recognition.

The optical isomers of the well known alpha 1-antagonist WB4101 and of its derivatives with a methyl group in the oxyethyl moiety were prepared for the evaluation of their alpha-adrenoceptors binding affinity. By means of a detailed computational analysis, the present work shows that the introduction of a methyl group affects the behaviour of WB4101 in different ways. A limitation of the conformational freedom in certain regions of the torsional subspace of the potential energy function, differences in the reactivity of the protonated species towards a model proton acceptor and the quality of the superposition with the rigid template for alpha 1 antagonists, corynanthine, are examined and discussed in order to select a candidate bioactive form and possible features which act as modulators of the recognition process at the alpha 1-adrenoceptors.