Drug metabolism-based design, synthesis, and bioactivities of 1-(2,6-dimethylphenoxy)-2-(3,4-dimethoxyphenylethylamino)propane hydrochloride (DDPH) analogs as α₁-adrenoceptors antagonists

Abstract

1-(2,6-dimethylphenoxy)-2-(3,4-dimethoxyphenylethylamino)propane hydrochloride (DDPH) is a potent α₁-adrenoceptor antagonist that is currently under Phase II clinic trials. However, the fast metabolism has restricted its further use. In this paper, 11 DDPH analogs were designed according to the probable metabolism pathways of DDPH, and featured the structures of halogen, methyl, and cyano groups at the 3-, or 4-position of aromatic ring A to block the hydroxylation, and one hydroxyl group at the 3-, or 4-position of aromatic ring B to extend the duration time. These compounds were synthesized in moderate to good yields from the reductive amination of substituted phenoxyacetones with substituted phenylethylamines, and fully characterized with ¹H NMR, IR, and HRMS. Biological evaluation indicated that most of the compounds exhibited strong blocking and moderate to good antihypertensive activities. It is clear that the compounds having 4-OH/3-OMe on group B exhibited higher blocking activities and longer duration time than their corresponding analogs having 4-OMe/3-OMe (and also 3-OH/4-OMe). Among them, compound 13 having bromo group at the 4-position of ring A and 4-OH/3-OMe on group B, exhibited the highest blocking activity, whereas compound 17 that had a methyl group at the 4-position of ring A and a hydroxyl group at the 4-position of ring B, was more active than potent DDPH in terms of both blocking and antihypertensive activities. In addition, the possible correlations between the blocking and antihypertensive activities are also briefly discussed.