(

1. A compound of the structure:

or a pharmaceutically acceptable salt thereof.

2. (2S,4R)-5-(5′-chloro-2′-fluorobiphenyl-4-yl)-4-(ethoxyoxalylamino)-2-hydroxymethyl-2-methylpentanoic acid.

3. A crystalline form of calcium (2S,4R)-5-(5′-chloro-2′-fluoro-[1,1′-biphenyl]-4-yl)-4-(2-ethoxy-2-oxoacetamido)-2-(hydroxymethyl)-2-methylpentanoate.

4. The crystalline form of claim 3 , wherein the crystalline form is characterized by a powder X-ray diffraction pattern comprising diffraction peaks at 20 values of 7.18±0.2, 7.38±0.2 and 7.97±0.2.

5. The crystalline form of claim 3 , wherein the crystalline form is characterized by a powder X-ray diffraction pattern comprising diffraction peaks at 20 values of 3.98±0.2, 5.00±0.2, 7.18±0.2, 7.38±0.2, 7.97±0.2, 8.87±0.2, and 10.91±0.2.

6. The crystalline form of claim 5 , wherein the crystalline form is further characterized by having one or more additional difrraction peaks at 20 values selected from 3.47±0.2, 9.99±0.2, 15.74±0.2, 15.98±0.2, and 18.98±0.2.

7. The crystalline form of claim 3 , wherein the crystalline form is characterized by a powder X-ray diffraction pattern in which the peak positions are substantially in accordance with the peak positions of the pattern shown in FIG. 1 .

8. The crystalline form of claim 3 , wherein the crystalline form is characterized by a differential scanning calorimetry trace recorded at a heating rate of 10° C. per minute which shows a maximum in endothermic heat flow at a temperature between about 237° C. and about 241° C.

9. The crystalline form of claim 3 , wherein the crystalline form is characterized by a differential scanning calorimetry trace substantially in accordance with that shown in FIG. 2 .

10. A pharmaceutical composition comprising the compound of claim 1 or the crystalline form of claim 3 and one or more pharmaceutically acceptable carriers.

11. The pharmaceutical composition of claim 10 , wherein the pharmaceutically acceptable carrier is magnesium stearate.

12. A pharmaceutical composition comprising the compound of claim 1 or the crystalline form of claim 3 and an AT 1 receptor antagonist, an angiotensin-converting enzyme inhibitor, a phosphodiesterase (PDE) inhibitor, a renin inhibitor, a diuretic, or combinations thereof, and optionally one or more pharmaceutically acceptable carriers.

13. An oral dosage form comprising the compound of claim 1 or the crystalline claim 3 in a capsule, tablet, liquid or suspension.

14. The oral dosage form of claim 13 wherein a release of the compound of claim 1 or the crystalline form of claim 3 in a subject is an immediate, controlled or delayed release.

15. The oral dosage form of claim 13 , wherein the capsule material is gelatin, polysaccharide, chitosan or synthetic polymers.

16. The oral dosage form of claim 13 , wherein the hard capsule comprises gelatin, polysaccharides, or synthetic polymers.

17. The oral dosage form of claim 13 , wherein the capsule comprises hydroxypropyl methylcellulose.

18. An intravenous dosage form comprising the compound of claim 1 or the crystalline form of claim 3 in a buffered solution.

19. A method for treating hypertension, heart failure, or renal disease, the method comprising administering to a patient a therapeutically effective amount of the compound of claim 1 or the crystalline form of claim 3 .

20. A method of treating a renally-impaired subject, the method comprising administering a therapeutically effective amount of the compound of claim 1 or the crystalline form of claim 3 to the subject.

21. The method according to claim 20 , wherein the renally-impaired subject has chronic kidney disease with an estimated glomerular filtration rate (eGFR) between 60 mL/min/1.73 m 2 and 15 mL/min/1.73 m 2 .

22. A process for preparing the compound of claim 1 , the process comprising (a) mixing ethanol and oxalyl chloride to form a solution; (b) reacting (2S,4R)-4-amino-5-(5′-chloro-2′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methylpentanoic acid benzyl ester with the solution; and (c) combining resulting mixture with palladium on carbon under hydrogen to yield the compound of claim 1 .

23. A process for preparing the compound of claim 1 , the process comprising:

(a) dissolving ethanol in dicloromethane;

(b) adding oxalyl chloride to form a solution and stirring at room temperature;

(c) evaporating solvent from solution;

(d) adding remaining solution to (2S,4R)-4-amino-5-(5′-chloro-2′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methylpentanoic acid benzyl ester that is first dissolved in dicloromethane;

(e) adding N,N-diisopropylethylamine and stirring a room temperature;

(f) evaporating solvent to form a solid;

(g) combining solid with palladium 10 wt % on carbon in solvent to form a mixture;

(h) placing mixture under hydrogen with stirring; and

(i) filtering off palladium on carbon and vacuum drying to yield the compound of claim 1 .

24. The process according to claim 23 , wherein the resulting solids in steps (0 and (i) are purified by chromatography.

25. A process for preparing the crystalline form of claim 3 , the process comprising:

(a) dissolving (2S,4R)-5-(5′-chloro-2′-fluorobiphenyl-4-yl)-4-(ethoxyoxalylamino)-2-hydroxymethyl-2-methylpentanoic acid in ethanol and N,N-diisopropylethylamine to form solution A;

(b) dissolving calcium trifluoromethane sulfonate in ethanol to form solution B;

(c) adding dropwise solution B to solution A to form a slurry;

(d) stirring at room temperature; and

(e) isolating the resulting solids to yield the crystalline form.

26. The process according to claim 25 , the process further comprising:

(f) cooling the crystalline form to about 5° C. and adding a cold ethanol:water mixture under vigorous stirring; and

(g) filtering and drying at room temperature to yield crystalline form.