Neprilysin inhibitors

1. A compound of formula I:

where:

R 1 is —OR 7 ;

R 2 is H;

X is

R 3 is absent or is selected from H; halo; —C 0-5 alkylene-OH; —NH 2 ; —C 1-6 alkyl; —CF 3 ; —C 3-7 cycloalkyl; —C 0-2 alkylene-O—C 1-6 alkyl; —C(O)R 20 ; —C 0-1 alkylene-COOR 21 ; —C(O)NR 22 R 23 ; —NHC(O)R 24 ; ═O; —NO 2 ; —C(CH 3 )═N(OH); phenyl optionally substituted with one or two groups independently selected from halo, —OH, —CF 3 , —OCH 3 , —NHC(O)CH 3 , and phenyl; naphthalenyl; pyridinyl; pyrazinyl; pyrazolyl optionally substituted with methyl; thiophenyl optionally substituted with methyl or halo; furanyl; and —CH 2 -morpholinyl; and R 3 , when present, is attached to a carbon atom;

R 4 is absent or is selected from H; —OH; —C 1-6 alkyl; —C 1-2 alkylene-COOR 35 ;

—CH 2 OC(O)CH(R 36 )NH 2 ; —OCH 2 OC(O)CH(R 36 )NH 2 ; —OCH 2 OC(O)CH 3 ; —CH 2 OP(O)(OH) 2 ;

—CH 2 CH(OH)CH 2 OH; —CH[CH(CH 3 ) 2 ]—NHC(O)O—C 1-6 alkyl; pyridinyl; and phenyl or benzyl optionally substituted with one or more groups selected from halo, —COOR 35 , —OCH 3 , —OCF 3 , and —SCF 3 ; and R 4 , when present, is attached to a carbon atom;

or R 3 and R 4 are taken together to form -phenylene-O—(CH 2 ) 1-3 - or -phenylene-O—CH 2 —CHOH—CH 2 —;

a is 0 or 1; R 5 is selected from halo, —CH 3 , —CF 3 , and —CN;

b is 0 or an integer from 1 to 3; each R 6 is independently selected from halo, —OH, —CH 3 , —OCH 3 , and —CF 3 ;

R 7 is selected from H, —C 1-8 alkyl, and

R 32 is —C 1-6 alkyl or —C 0-6 alkylene-C 6-10 aryl;

R 20 is selected from H and —C 1-6 alkyl;

R 21 and R 35 are independently selected from H, —C 1-6 alkyl, —C 1-3 alkylene-C 6-10 aryl, —C 1-3 alkylene-C 1-9 heteroaryl, —C 3-7 cycloalkyl, —[(CH 2 ) 2 O] 1-3 CH 3 , —C 1-6 alkylene-OC(O)R 25 , —C 1-6 alkylene-NR 27 R 28 , —C 1-6 alkylene-C(O)R 33 , —C 0-6 alkylenemorpholinyl, —C 1-6 alkylene-SO 2 —C 1-6 alkyl,

R 25 is selected from —C 1-6 alkyl, —O—C 1-6 alkyl, —C 3-7 cycloalkyl, —O—C 3-7 cycloalkyl, phenyl, —O-phenyl, —NR 27 R 28 , —CH[CH(CH 3 ) 2 ]—NH 2 , CH[CH(CH 3 ) 2 ]—NH 2 , —CH[CH(CH 3 ) 2 ]—NHC(O)O—C 1-6 alkyl, and —CH(NH 2 )CH 2 COOCH 3 ;

R 27 and R 28 are independently selected from H, —C 1-6 alkyl, and benzyl; or R 27 and R 28 are taken together as —(CH 2 ) 3-6 —, —C(O)—(CH 2 ) 3 —, or —(CH 2 ) 2 O(CH 2 ) 2 —; R 33 is selected from —O—C 1-6 alkyl, —O-benzyl, and —NR 27 R 28 ; and R 34 is —C 1-6 alkyl or —C 0-6 alkylene-C 6-10 aryl;

R 22 and R 23 are independently selected from H, —C 1-6 alkyl, —CH 2 COOH, —(CH 2 ) 2 OH, —(CH 2 ) 2 OCH 3 , —(CH 2 ) 2 SO 2 NH 2 , —(CH 2 ) 2 N(CH 3 ) 2 , —C 0-1 alkylene-C 3-7 cycloalkyl, and —(CH 2 ) 2 -imidazolyl; or R 22 and R 23 are taken together to form a saturated or partially unsaturated —C 3-5 heterocycle optionally substituted with halo, —OH, —COOH, or —CONH 2 ; and optionally containing an oxygen atom in the ring;

R 24 is selected from —C 1-6 alkyl; —C 0-1 alkylene-O—C 1-6 alkyl; phenyl optionally substituted with halo or —OCH 3 ; and —C 1-9 heteroaryl; and

R 36 is selected from H, —CH(CH 3 ) 2 , phenyl, and benzyl;

where each alkyl group in R 1 , R 3 , and R 4 is optionally substituted with 1 to 8 fluoro atoms; and;

where the methylene linker on the biphenyl is optionally substituted with one or two —C 1-6 alkyl groups or cyclopropyl;

or a pharmaceutically acceptable salt thereof.

2. The compound of claim 1 , where:

R 3 is absent or is selected from H; halo; —C 0-5 alkylene-OH; —C 1-6 alkyl; —C 3-7 cycloalkyl; —C 0-2 alkylene-O—C 1-6 alkyl; —C(O)R 20 ; —C 0-1 alkylene-COOR 21 ; —NHC(O)R 24 ; phenyl optionally substituted with one or two groups independently selected from halo, —OH, and —OCH 3 ; pyrazolyl optionally substituted with methyl; and —CH 2 -morpholinyl; and R 3 , when present, is attached to a carbon atom;

R 4 is absent or is selected from H; —OH; and R 4 , when present, is attached to a carbon atom;

a is 0;

b is 0 or an integer from 1 to 3; each R 6 is halo;

R 7 is selected from H, —C 1-8 alkyl, and

R 32 is —C 1-6 alkyl;

R 20 is H or —C 1-6 alkyl;

R 21 is H;

R 24 is a phenyl optionally substituted with halo or —OCH 3 ; and

where each alkyl group in R 1 , R 3 , and R 4 is optionally substituted with 1 to 8 fluoro atoms.

3. The compound of claim 2 , where:

R 3 is H; halo, —OH, —C 1-6 alkyl; —C 3-7 cycloalkyl; —O—C 1-6 alkyl; —C(O)R 20 ; —COOR 21 ; —NHC(O)R 24 ; phenyl optionally substituted with one or two groups independently selected from halo, —OH, and —OCH 3 ; pyrazolyl optionally substituted with methyl; or —CH 2 -morpholinyl;

R 4 is H;

b is an integer from 1 to 3; and each R 6 is halo.

4. The compound of claim 3 , where:

R 3 is H; —C 1-6 alkyl; or phenyl;

R 6 is chlorine or fluorine; and

R 7 is H.

5. A compound selected from:

(a) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-[(3-hydroxyisoxazole-5-carbonyl)amino]pentanoic acid ethyl ester;

(b) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-[(3-hydroxyisoxazole-5-carbonyl)amino]pentanoic acid;

(c) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-[(3-hydroxyisoxazole-5-carbonyl)amino]pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester;

(d) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-[(3-methoxyisoxazole-5-carbonyl)amino]-pentanoic acid;

(e) (2R,4R)-5-Biphenyl-4-yl-4-{[3-(4-chlorophenyl)-isoxazole-5-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(f) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-{[3-(2-methoxy-benzoylamino)-isoxazole-5-carbonyl]-amino}-pentanoic acid;

(g) (2R,4R)-5-Biphenyl-4-yl-4-{[3-(2-chlorophenyl)-isoxazole-5-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(h) (2R,4R)-5-Biphenyl-4-yl-4-[(3-cyclohexyl-isoxazole-5-carbonyl)-amino]-2-hydroxy-pentanoic acid;

(i) (2R,4R)-5-Biphenyl-4-yl-4-{[3-(3-fluorophenyl)-isoxazole-5-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(j) (2R,4R)-5-Biphenyl-4-yl-4-{[3-(2-fluorophenyl)-isoxazole-5-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(k) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-{[3-(1-methyl-1H-pyrazol-4-yl)-isoxazole-5-carbonyl]-amino}-pentanoic acid;

(l) (2R,4R)-5-Biphenyl-4-yl-4-{[3-(2,5-dichlorophenyl)-isoxazole-5-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(m)(2R,4R)-5-Biphenyl-4-yl-4-{[3-(3,4-dichlorophenyl)-isoxazole-5-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(n) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-{[3-(2-methoxy-phenyl)-isoxazole-5-carbonyl]-amino}-pentanoic acid;

(o) 5-((1R,3R)-1-Biphenyl-4-ylmethyl-3-carboxy-3-hydroxy-propylcarbamoyl)-isoxazole-3-carboxylic acid;

(p) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-{[5-(2-methoxy-phenyl)-isoxazole-3-carbonyl]-amino}-pentanoic acid;

(q) (2R,4R)-5-Biphenyl-4-yl-4-{[5-(2-chlorophenyl)-isoxazole-3-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(r) (2R,4R)-5-Biphenyl-4-yl-4-{[5-(4-chlorophenyl)-isoxazole-3-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(s) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-{[5-(3-methoxy-phenyl)-isoxazole-3-carbonyl]-amino}-pentanoic acid;

(t) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-[(5-morpholin-4-ylmethyl-isoxazole-3-carbonyl)-amino]-pentanoic acid;

(u) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-{[5-(4-methoxy-phenyl)-isoxazole-3-carbonyl]-amino}-pentanoic acid;

(v) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-{[5-(2-hydroxy-phenyl)-isoxazole-3-carbonyl]-amino}-pentanoic acid;

(w) (2R,4R)-5-Biphenyl-4-yl-4-{[5-(2-chlorobenzoylamino)-isoxazole-3-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(x) (2R,4R)-5-Biphenyl-4-yl-2-hydroxy-4-[(2-phenyl-oxazole-5-carbonyl)-amino]-pentanoic acid;

(y) (2R,4R)-4-[(3-Acetyl-isoxazole-5-carbonyl)-amino]-5-(3′-chlorobiphenyl-4-yl)-2-hydroxy-pentanoic acid;

(z) (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-[(3-methoxy-isoxazole-5-carbonyl)-amino]-pentanoic acid;

(aa) (2R,4R)-5-(3′-Chloro-biphenyl-4-yl)-4-[(3-chloro-isoxazole-5-carbonyl)-amino]-2-hydroxy-pentanoic acid;

(bb) (2R,4R)-5-(3′-Chloro-biphenyl-4-yl)-2-hydroxy-4-[(3-isopropyl-isoxazole-5-carbonyl)-amino]-pentanoic acid;

(cc) (2R,4R)-5-(3′-Chloro-biphenyl-4-yl)-2-hydroxy-4-[(3-propyl-isoxazole-5-carbonyl)-amino]-pentanoic acid;

(dd) (2R,4R)-5-(3′-Chloro-biphenyl-4-yl)-2-hydroxy-4-[(3-isobutyl-isoxazole-5-carbonyl)-amino]-pentanoic acid;

(ee) (2R,4R)-5-(3′-Chloro-biphenyl-4-yl)-2-hydroxy-4-{[3-(1-hydroxy-1-methyl-ethyl)-isoxazole-5-carbonyl]-amino}-pentanoic acid;

(ff) (2R,4R)-4-[(3-tert-Butyl-isoxazole-5-carbonyl)-amino]-5-(3′-chloro-biphenyl-4-yl)-2-hydroxy-pentanoic acid;

(gg) (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-4-{[5-(2-chlorophenyl)-isoxazole-3-carbonyl]-amino}-2-hydroxy-pentanoic acid;

(hh) (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-{[5-(2-hydroxyphenyl)-isoxazole-3-carbonyl]-amino}-pentanoic acid; or

a pharmaceutically acceptable salt thereof.

6. A pharmaceutical composition comprising the compound of any one of claims 1 - 5 and a pharmaceutically acceptable carrier.

7. The pharmaceutical composition of claim 6 , further comprising a therapeutic agent selected from adenosine receptor antagonists, α-adrenergic receptor antagonists, β 1 -adrenergic receptor antagonists, β 2 -adrenergic receptor agonists, dual-acting β-adrenergic receptor antagonist/α 1 -receptor antagonists, advanced glycation end product breakers, aldosterone antagonists, aldosterone synthase inhibitors, aminopeptidase N inhibitors, androgens, angiotensin-converting enzyme inhibitors and dual-acting angiotensin-converting enzyme/neprilysin inhibitors, angiotensin-converting enzyme 2 activators and stimulators, angiotensin-II vaccines, anticoagulants, anti-diabetic agents, antidiarrheal agents, anti-glaucoma agents, anti-lipid agents, antinociceptive agents, anti-thrombotic agents, AT 1 receptor antagonists and dual-acting AT 1 receptor antagonist/neprilysin inhibitors and multifunctional angiotensin receptor blockers, bradykinin receptor antagonists, calcium channel blockers, chymase inhibitors, digoxin, diuretics, dopamine agonists, endothelin converting enzyme inhibitors, endothelin receptor antagonists, HMG-CoA reductase inhibitors, estrogens, estrogen receptor agonists and/or antagonists, monoamine reuptake inhibitors, muscle relaxants, natriuretic peptides and their analogs, natriuretic peptide clearance receptor antagonists, neprilysin inhibitors, nitric oxide donors, non-steroidal anti-inflammatory agents, N-methyl d-aspartate receptor antagonists, opioid receptor agonists, phosphodiesterase inhibitors, prostaglandin analogs, prostaglandin receptor agonists, renin inhibitors, selective serotonin reuptake inhibitors, sodium channel blocker, soluble guanylate cyclase stimulators and activators, tricyclic antidepressants, vasopressin receptor antagonists, and combinations thereof.

8. The pharmaceutical composition of claim 7 , wherein the therapeutic agent is an AT 1 receptor antagonist.

9. A method for treating hypertension, heart failure, or renal disease, comprising administering to a patient a therapeutically effective amount of the compound of any one of claims 1 - 5 .