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In an attempt to change the beta-adrenergic properties of completely aliphatic 3-(methyleneaminoxy)propanolamine derivatives, from antagonist to agonist, while still retaining the beta 2-selectivity, we described, in a previous paper, the synthesis of a series of such derivatives possessing a hydroxy or methoxy group linked to the aliphatic substituent present on the oximic carbon. However, pharmacological tests indicated that these compounds maintain the competitive antagonism on beta receptors. In this paper, the synthesis and the results of functional tests on isolated preparations are reported for a new series of 3-(substituted-benzylideneaminoxy)propanolamine derivatives in which either the hydroxy or the methoxy group is linked to a phenyl ring present on the oximic carbon. The results obtained are then discussed, taking into account the conformational and reactivity properties of these compounds, determined by means of theoretical calculations.

The N-isopropyl- and N-t-butyl-substituted 1-[o-(3-amino-2-hydroxypropoxy)benzylideneaminoxy]-3-amino-2-propa nols (7a,b) and their meta (8a,b) and para (9a,b) isomers, in which a single aromatic ring is substituted both by the oxypropanolaminic chain of (aryloxy)propanolaminic beta-adrenergic antagonists (AOPAs) and the [(methyleneamino)oxy]propanolaminic chain of [(methyleneamino)oxy]-propanolaminic beta-blocking drugs (MAOPAs), were synthesized and assayed for their beta-adrenergic activity by functional tests on isolated preparations. Compounds 7-9 represent a new type of molecular duplication of beta-adrenergic drugs, formally deriving from the sharing of the aromatic portions of two different pharmacophoric subunits, namely the (aryloxy)propanolaminic portion of AOPAs and the [(benzylideneamino)oxy]propanolaminic portion of aryl-substituted MAOPAs. The pharmacological results showed that the beta-blocking activity of compounds 7-9 is closely related to the way in which the two subunits are linked by the aromatic nucleus: the activity decreases on passing from the ortho-compounds (7a,b) to the meta (8a,b) and then to the para (9a,b) isomers. A comparison of this activity trend with those found for series of both beta-blocking AOPAs and aryl-substituted MAOPAs seems to indicate that compounds 7-9 can be considered more as AOPAs substituted on the phenyl ring by a [(methyleneamino)oxy]propanolaminic chain rather than as aromatic MAOPAs substituted on the same phenyl moiety by an oxypropanolaminic portion.

In a previous paper, it had been found that completely aliphatic 3-(methylene aminoxy)propanolamine derivatives showed a good beta-blocking adrenergic activity directed prevalently towards beta 2-tracheal receptors. In an attempt to change the beta-adrenergic properties of these compounds from antagonist to agonist, while still retaining the beta 2-selectivity, a series of new completely aliphatic 3-(methyleneaminoxy)propanolamine derivatives were designed in which either a hydroxylic or a methoxylic group was present on the aliphatic portion linked to the oximic carbon. The synthesis of the new compounds and their beta-adrenergic activity, evaluated by means of functional tests on isolated preparations, are described and discussed; the results obtained are then rationalised on the basis of their conformational and reactivity characteristics, determined by means of theoretical methods.