Novel monocyclic amide-linked phenol derivatives without mitochondrial toxicity have potent uric acid-lowering activity.

Although benzbromarone (BBR) is a conventional, highly potent uricosuric drug, it is not a standard medicine because it causes rare but fatal fulminant hepatitis. We transformed the bis-aryl ketone structure of BBR to generate novel monocyclic amide-linked phenol derivatives that should possess uric acid excretion activity without adverse properties associated with BBR. The derivatives were synthesized and tested for uric acid uptake inhibition (UUI) in two assays using either urate transporter 1-expressing cells or primary human renal proximal tubule epithelial cells. We also evaluated their inhibitory activity against mitochondrial respiration as a critical mitochondrial toxicity parameter. Some derivatives with UUI activity had no mitochondrial toxicity, including compound 3f, which effectively lowered the plasma uric acid level in Cebus apella. Thus, 3f is a promising candidate for further development as a uricosuric agent.

Systematic Structure-Activity Relationship (SAR) Exploration of Diarylmethane Backbone and Discovery of A Highly Potent Novel Uric Acid Transporter 1 (URAT1) Inhibitor.

In order to systematically explore and better understand the structure-activity relationship (SAR) of a diarylmethane backbone in the design of potent uric acid transporter 1 (URAT1) inhibitors, 33 compounds (1a-1x and 1ha-1hi) were designed and synthesized, and their in vitro URAT1 inhibitory activities (IC50) were determined. The three-round systematic SAR exploration led to the discovery of a highly potent novel URAT1 inhibitor, 1h, which was 200- and 8-fold more potent than parent lesinurad and benzbromarone, respectively (IC50 = 0.035 µM against human URAT1 for 1h vs. 7.18 µM and 0.28 µM for lesinurad and benzbromarone, respectively). Compound 1h is the most potent URAT1 inhibitor discovered in our laboratories so far and also comparable to the most potent ones currently under development in clinical trials. The present study demonstrates that the diarylmethane backbone represents a very promising molecular scaffold for the design of potent URAT1 inhibitors.

A convergent synthetic study of biologically active benzofuran derivatives.

In order to construct a benzofuran library, we developed a model study of benzbromarone. Synthesis has been achieved in 53% overall yield, starting from phenol via the key intermediate 2-ethylbenzofuran which was afforded by intramolecular Wittig reaction.

Studies on uricosuric diuretics. III. Substituted 1,3-dioxolo[4,5-f]-1,2-benzisoxazole-6-carboxylic acids and 1,3-dioxolo[4,5-g]-1,2-benzisoxazole-7-carboxylic acids.

A series of substituted 1,3-dioxolo[4,5-f]-1,2-benzisoxazole-6-carboxylic acids 13 and 1,3-dioxolo[4,5-g]-1,2-benzisoxazole-7-carboxylic acids 14 were synthesized and evaluated for diuretic and uricosuric activities in rats. Most of the benzisoxazole derivatives 13 and 14 showed potent diuretic activities. Moderate uricosuric activities were also found in 14a, 14b, and 14f.

Aryloxyacetic acid diuretics with uricosuric activity. II. Substituted [(4-oxo-4H-1-benzopyran-7-yl)oxy]acetic acids and the related compounds.

Di- and tri-substituted [(4-oxo-4H-1-benzopyran-7-yl)oxy]acetic acids, and 4-oxo-3-phenyl-4H-furo[2,3-h]-[1]benzopyran-8-carboxylic acid were synthesized and tested for natriuretic and uricosuric activities. Among the compounds tested, 3,5-disubstituted [(4-oxo-4H-1-benzopyran-7-yl)oxy]acetic acids (6c-f, h, n and x) showed potent natriuretic and uricosuric activities, whereas 4-oxo-3-phenyl-4H-furo[2,3-h][1]benzopyran-8-carboxylic acid (6dd) possessed only potent natriuretic activity. The structure-activity relationships are also discussed.

Aryloxy acetic acid diuretics with uricosuric activity. I. Polycyclic aryloxy acetic acids.

In order to obtain lead compounds for uricosuric diuretics, various polycyclic aryloxy acetic acids [isoindole derivative (7), quinazoline derivative (15), benzopyran derivative (20), xanthone derivative (24), benzofuran derivative (30) and indene derivative (36)] were prepared. These compounds were evaluated for diuretic activity in rats, uricosuric activity in rats and antihypertensive activity in 11-deoxycorticosterone acetate (DOCA)/salt hypertensive rats. Among the compounds, 20 showed potent diuretic, uricosuric and moderate antihypertensive activities. Therefore, we selected 20 as a lead compound for development of new uricosuric diuretics.

Studies on uricosuric diuretics. II. Substituted 7,8-dihydrofuro[2,3-g]-1,2-benzisoxazole-7-carboxylic acids and 7,8-dihydrofuro[2,3-g]benzoxazole-7-carboxylic acids.

A series of substituted 7,8-dihydrofuro[2,3-g]-1,2-benzisoxazole-7-carboxylic acids 9 and 7,8-dihydrofuro[2,3-g]benzoxazole-7-carboxylic acids 12 were synthesized and evaluated for uricosuric and diuretic activities in rats. Many of the benzisoxazole derivatives 9 showed uricosuric and only weak diuretic activities, whereas the benzoxazoles 12 exhibited potent diuretic activities with little affecting urate excretion. Among these compounds, 5-chloro-7,8-dihydro-3-phenylfuro[2,3-g]-1,2-benzisoxazole-7-carbo xylic acid (9b, AA-193) was found to be a potent uricosuric agent without diuretic activity and was selected for further development.

Studies on uricosuric diuretics. I. Syntheses and activities of xanthonyloxyacetic acids and dihydrofuroxanthone-2-carboxylic acids.

A series of substituted xanthonyloxyacetic acids (5 and 6), 1,2-dihydrofuro[2,3-c]xanthone-2-carboxylic acids (7) and 2,3-dihydrofuro[3,2-b]xanthone-2-carboxylic acids (8) were synthesized and tested for diuretic and uricosuric activities in rats. Most of the xanthon-3-yloxyacetic acids (5) and 7 showed potent diuretic activities, while 8 had lower activities. Uricosuric activities were found in 5c, 5f, 5k, 5m, 5o, 5p, 5r, 7m, 7p and 8q.

Substituted 5,6-dihydrofuro[3,2-f]-1,2-benzisoxazole-6-carboxylic acids: high-ceiling diuretics with uricosuric activity.

A series of substituted 5,6-dihydrofuro[3,2-f]-1,2-benzisoxazoles was prepared and evaluated for their saluretic and uricosuric properties. Pharmacological evaluation of the title compounds was carried out in mice, rats, dogs, and monkeys. The diuretic/saluretic nature of these compounds was observed in all species, whereas the uricosuric activity was best seen in the Cebus monkey. Evaluation of the enantiomers of 8-chloro-3-(o-fluorophenyl)-5,6-dihydrofuro [3,2-f]-1,2-benzisoxazole-6-carboxylic acid (15k) revealed that only the (+) enantiomer (29) displayed diuretic and saluretic activity, whereas both enantiomers possessed uricosuric activity. X-ray analysis showed that the (-) enantiomer (30) possesses the 2R configuration.

(Acylaryloxy)acetic acid diuretics. 5. [(2-Alkyl- and 2,2-disubstituted-1,3-dioxo-5-indanyl)oxy]acetic acids.

Investigation of the chemistry of the potent uricosuric diuretic indacrinone (MK-196) prompted the synthesis of a series of 3-oxo derivatives, i.e., the indan-1,3-diones. In general, both pharmacological parameters (uricosuria and diuresis) were significantly less pronounced with the 1,3-diones than with the parent 1-oxo compounds.

(Acylaryloxy)acetic acid diuretics. 3. 2,3-Dihydro-5-acyl-2-benzofurancarboxylic acids, a new class of uricosuric diuretics.

The discovery that dihydroethacrynic acid and other (4-acylphenoxy)acetic acids possessed modest but significant uricosuric and diuretic activity prompted our investigation of the related 2,3-dihydro-5-acyl-2-bensofurancarboxylic acids. Synthetic routes to a number of these compounds are presented along with the structure-activity relationships generated from studies in rats, dogs, and chimpanzee. Examination of the enantiomers of 6,7-dichloro-2,3-dihydro-5-(2-thienylcarbonyl)-2-benzofurancarboxylic acid (10c) in the chimpanzee revealed that all diuretic and saluretic activity is due to the (+) enantiomer 10d, while the (-) enantiomer 10e is responsible for all of the uricosuric activity. X-ray analysis showed that the (-) enantiomer 10e possesses the 2R configuration.

(Acylaryloxy)acetic acid diuretics. 4. Indeno[5,4-b]furan-2-carboxylic acids.

Investigation of the chemistry of the potent new uricosuric diuretic indacrinone (MK-196) led to a class of novel annulated derivatives, indeno[5,4-b]furan-2-carboxylic acids. The structural requirements for optimal diuretic and uricosuric activity of the tricyclic analogues differed from those of their (indanyloxy)acetic acids counterparts. Most notably, the tricyclic analogues were two to four times more natriuretic than the corresponding (indanyloxy)acetic acids when administered orally to rats, and in chimpanzees, uricosuria was observed only in those indenofurans having a nuclear aryl substituent.

(Acylaryloxy)acetic acid diuretics. 2. (2-Alkyl-2-aryl-1-oxo-5-indanyloxy)acetic acids.

The introduction of an aryl group at the 2 position of the uricosuric diuretics, (1-oxo-2-alkyl-5-indanyloxy)acetic acids, provided compounds with markedly increased potency over their monosubstituted precursors. These compounds were synthesized either by arylation of the corresponding 2-alkyl-5-methoxy-1-indanones with diaryliodonium salts or by alkylation of the 2-aryl-5-methoxy-1-indanones which were cleaved to the corresponding phenols and then converted to the desired oxyacetic acids. Systematic structural variation of the 2-arylindanyloxyacetic acids provided aryl-substituted compounds with varying degrees of uricosuric and diuretic activity.

(Acylaryloxy)acetic acid diuretics. 1. (2-Alkyl- and 2,2-dialkyl-1-oxo-5-indanyloxy)acetic acids.

The discovery of the (acryloylaryloxy)acetic acids as a new class of potent diuretics prompted the investigation of related bicyclic compounds. Annelated analogues of the parent series, the (2-alkyl- and 2,2-dialkyl-1-oxo-5-indanyloxy)acetic acids, were the subjects of this study. Those compounds, unlike the monocyclic parent compound, lacked the double bond adjacent to the carbonyl group. More importantly, they possessed both saluretic and uricosuric properties. The optimal single 2-substituents for maximal saluretic and uricosuric activity were determined. In general, better activity was observed when a second 2-alkyl substituent (especially methyl) was present in the molecule. Replacement of the carboxy substituent by 5-tetrazolyl generally resulted in a reduction in activity.