QSAR study for a novel series of ortho disubstituted phenoxy analogues of α1-adrenoceptor antagonist WB4101

On the basis of the affinities at the α1a-, α1b- and α1d-adrenoceptors and the 5-HT1A receptor of a previous series of sixteen 2-[(2-phenoxyethyl)aminomethyl]-1,4-benzodioxanes ortho monosubstituted at the phenoxy moiety, a number of ortho disubstituted analogues were designed, synthesized in both the enantiomeric forms and tested in binding assays on the same receptors. The affinity values of the new compounds 1–11 were compared with those of the enantiomers of the 2,6-dimethoxyphenoxy analogue, the well-known α1 antagonist WB4101, and of the ortho monosubstituted derivatives, suggesting some distinctive aspects of the interaction of the phenoxy moiety, in particular with the α1a-AR and the 5-HT1A receptor, of the monosubstituted and the disubstituted compounds. A classical quantitative structure-activity relationship (Hansch) analysis was applied to the whole set of the S enantiomers of the ortho mono- and disubstituted WB4101 analogues (26 compounds), finding a very good correlation for the α1a affinity. For this latter, a significant parabolic relationship was also found with the volume of the two ortho substituents. Diametrically opposite, the same relationships for the 5-HT1A exhibit low or insignificant correlation coefficients.

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