Topically active carbonic anhydrase inhibitors. 2. Benzo[b]thiophenesulfonamide derivatives with ocular hypotensive activity

Derivatives of benzo[b]thiophene-2-sulfonamide were prepared to investigate their potential utility as topically active inhibitors of ocular carbonic anhydrase. Such an agent would be useful in the treatment of glaucoma. Among the compounds described are 6-hydroxybenzo[b]thiophene-2-sulfonamide (16) and its acetate ester (23), which are among the most potent ocular hypotensive agents in this class, as assessed in the alpha-chymotrypsinized rabbit. These compounds were selected for clinical evaluation.

Thienothiopyran-2-sulfonamides: a novel class of water-soluble carbonic anhydrase inhibitors

An attempt to develop a water-soluble carbonic anhydrase inhibitor focused on exploring structure-activity relationships in the thienothiopyransulfonamide class. The strategy to influence water solubility while retaining carbonic anhydrase activity involved the introduction of a hydroxyl moiety and adjusting the oxidation state of the sulfur on the thiopyran portion of the molecule. Compounds 4 and 17 best fit the criteria of aqueous solubility and inhibitory potency vs. human carbonic anhydrase II and are candidates for evaluation as topically effective antiglaucoma agents.

Beta 1-selective adrenoceptor antagonists: examples of the 2-[4-[3-(substituted amino)-2-hydroxypropoxy]phenyl]imidazole class. 2

An attempt to develop a highly cardioselective beta-adrenoceptor antagonist devoid of intrinsic sympathomimetic activity (ISA) focused on exploring structure-activity relationships around (S)-[p-[3-[[2-(3,4-dimethoxyphenyl)ethyl]amino]-2-hydroxypropoxy] phenyl]-4-(2-thienyl)imidazole. Strategies to reduce or eliminate ISA centered on structural changes that could influence activation of the receptor by the drug itself or by a metabolite. The approaches involved (a) eliminating the acidic imidazole N-H proton, (b) incorporating substituents ortho to the beta-adrenergic blocking side chain, (c) increasing steric bulk around the N-H moiety, (d) decreasing lipophilicity, (e) introducing intramolecular hydrogen bonding involving the imidazole N-H, and (f) displacing the imidazole ring from an activating position by the incorporation of a spacer element. The compounds were investigated in vitro for beta-adrenoceptor antagonism and in vivo for ISA. From these studies, the most successful variation involved the insertion of a spacer between the imidazole and aryl rings. (S)-4-Acetyl-2-[[4-[3-[[2-(3, 4-dimethoxyphenyl)ethyl]amino]-2-hydroxypropoxy]phenyl]methyl] imidazole (S-51) was demonstrated to be highly cardioselective (dose ratio beta 2/beta 1 greater than 9333) and devoid of ISA.

Beta 1-selective adrenoceptor antagonists: examples of the 2-[4-[3-(substituted-amino)-2-hydroxypropoxy]phenyl]imidazole class

A series of 2-[4-[3-(substituted-amino)-2-hydroxypropoxy]phenyl]imidazoles is described. The compounds were investigated in vitro for beta-adrenoceptor antagonism, and several examples were found to be selective for the beta 1-adrenoceptor. The structure--activity relationship exhibited by this series of compounds is discussed. (S)-2-[p-[3-[[2-(3,4-dimethoxyphenyl)ethyl]amino]-2-hydroxypropoxy]phenyl]-4-(2 -thienyl)imidazole [(S)-13] was over 100 times more selective than atenolol for the beta 1-adrenergic receptor and has been selected for in-depth studies.

Trichloroacetamidines, a new class of positive inotropic agents

A series of trichloroacetamidine derivatives, obtained by addition of amines to trichloroacetonitrile, was evaluated for positive inotropic activity on isolated cat heart papillary muscles. Increased contractility, not antagonized by beta-adrenergic blockade with sotalol or reserpine pretreatment, was observed in this assay with a variety of N-substituted trichloroacetamidine derivatives. More extensive pharmacological studies with the 3-indolylmethyl analogue 2 showed that this amidine in dogs, 5 mg/kg iv, produced a positive inotropic effect more pronounced than that of ouabain, 50 microgram/kg iv. Several of the trichloroacetamidines were found to be inhibitors of guinea pig kidney and calf heart Na-K-dependent ATPase and to have specificity for these enzymes different from that of ouabain. Bacterial mutagenic activity was observed with three members, 2,3, and 12, of the series.

Synthesis and antihypertensive activity of some ester progenitors of methyldopa

A variety of esters of methyldopa was synthesized with the objective of obtaining derivatives that would be more efficiently absorbed from the gastrointestinal tract than the free amino acid and would undergo conversion to methyldopa readily in the blood or target tissues. Two of the esters, alpha-pivaloyloxyethyl (4u) and alpha-succinimidoethyl (4w), were found to be more potent antihypertensive agents than methyldopa in animal models and were selected for further study in man. The amino esters were prepared by three different methods, including direct esterification of methyldopa without the use of N- or O-protecting groups.