Phosphinic amide prodrugs of tenofovir

1. A compound of Formula I:

or a pharmaceutically acceptable salt thereof, wherein:

R 1 is (a) —C 1-4 alkyl, (b) —C 1-4 alkyl substituted with —OH, —SH, —SCH 3 , —NH 2 , —NH—C(═NH)—NH 2 , (c) —CH 2 -phenyl, (d) —CH 2 -phenol, (e) —(CH 2 ) 1-2 —COOH, (f) —(CH 2 ) 1-2 —CONH 2 , (g) —CH 2 -1H-indole, (h) —CH 2 -imidazole, (i) aryl or (j) heteroaryl;

R 2 is (a) —C 1-4 alkyl, (b) —C 1-4 alkyl substituted with —OH, —SH, —SCH 3 , —NH 2 , —NH—C(═NH)—NH 2 , (c) —CH 2 -phenyl, (d) —CH 2 -phenol, (e) —(CH 2 ) 1-2 —COOH, —(CH 2 ) 1-2 —CONH 2 , (g) —CH 2 -1H-indole, (h) —CH 2 -imidazole, (i) aryl or (j) heteroaryl;

or R 1 and R 2 are joined together with the carbon to which they are both attached to form —C 3-6 cycloalkyl or a 4 to 6-membered heterocyclic ring;

R 3 is —CN, —CF 3 , phenyl, heteroaryl, —C(O)OR 5b , —C(O)—N(R 6a ) (R 6b ), —S(O) 2 R 5b or —S(O) 2 —N(R 6a )(R 6b ), wherein each of phenyl and heteroaryl is unsubstituted or substituted with one to three substituents independently selected at each occurrence from R 10 ;

R 4 is —H, —CN, —CF 3 , phenyl, heteroaryl, —C(O)OR 5c or —C(O)—N(R 6c )(R 6d ), —S(O) 2 R 5c or —S(O) 2 —N(R 6c )(R 6d ), wherein each of phenyl and heteroaryl is unsubstituted or substituted with one to three substituents independently selected at each occurrence from R 10 ;

R 5a , R 5b and R 5c are each independently:

(a) —C 1-10 alkyl unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —CN, —CF 3 , —NR 7a R 7b , —OR 8 , —SH, —C 3-6 cycloalkyl or spiro-C 3-6 cycloalkyl,

(b) —CH 2 -phenyl unsubstituted or substituted with one to three substituents, wherein each substituent is independently selected at each occurrence from R 10 ,

(c) —C 3-8 cycloalkyl unsubstituted or substituted with one to three substituents, wherein each substituent is independently selected at each occurrence from R 10 ,

(d) aryl unsubstituted or substituted with one to three substituents, wherein each substituent is independently selected at each occurrence from R 10 ,

(e) —C 1-5 alkyl-X—C 1-5 alkyl wherein X is O, S or NH,

(f) heteroaryl unsubstituted or substituted with one to three substituents, wherein each substituent is independently selected at each occurrence from R 10 , or

(g) a heterocyclic ring unsubstituted or substituted with one to three substituents, wherein each substituent is independently selected at each occurrence from R 10 ;

R 6a , R 6b , R 6c and R 6d are each independently —H, —C 1-3 alkyl or —C 3-6 cycloalkyl;

R 7a and R 7b are each independently —H, —C 1-3 alkyl or —C 3-6 cycloalkyl;

R 8 is —H or —C 3-6 cycloalkyl; and

R 9 is —H, —C 1-3 alkyl or —C 3-6 cycloalkyl; and

R 10 is fluoro, chloro, bromo, —CN, —CF 3 , —NR 7a R 7b , —OR 9 , —SH or —C 1-3 alkyl.

2. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 1 and R 2 are both the same and are selected from methyl, ethyl, propyl or i-propyl.

3. The compound of claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 1 and R 2 are both methyl.

4. The compound of claim 2 , or a pharmaceutically acceptable salt thereof, wherein R 3 is

(a) —C 1-8 alkyl, —CH 2 CH 2 OH, —CH 2 CH 2 CH 2 OH, —CH 2 CH 2 SH, —CH 2 CH 2 CH 2 SH, —CH 2 CH 2 NH 2 , —CH 2 CH 2 CH 2 NH 2 , —CH 2 CF 2 CH 3 or —CH 2 CH 2 CF 3 ;

(b) —CH 2 -phenyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8a , —SH, —NR 6 R 7 or —C 1-3 alkyl,

(c) —C 3-6 cycloalkyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8a , —SH, —NR 6 R 7 or —C 1-3 alkyl,

(d) phenyl or naphthyl, each unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8a , —SH, —NR 6 R 7 or —C 1-3 alkyl,

(e) —CH 2 CH 2 OCH 3 , —CH 2 CH 2 CH 2 OCH 3 , —CH 2 CH 2 SCH 3 , —CH 2 CH 2 CH 2 SCH 3 , —CH 2 CH 2 NHCH 3 , —CH 2 CH 2 CH 2 NHCH 3 ,

(f) pyridyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8a , —SH, —NR 6 R 7 or —C 1-3 alkyl, or

(g) piperidinyl, pyrrolidinyl, tetrahydrofuranyl, or tetrahydropyranyl, each unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8a , —SH, —NR 6 R 7 or —C 1-3 alkyl.

5. The compound of claim 4 , or a pharmaceutically acceptable salt thereof, wherein R 4 is

(a) —C 1-8 alkyl, —CH 2 CH 2 OH, —CH 2 CH 2 CH 2 OH, —CH 2 CH 2 SH, —CH 2 CH 2 CH 2 SH, —CH 2 CH 2 NH 2 , —CH 2 CH 2 CH 2 NH 2 , —CH 2 CF 2 CH 3 or —CH 2 CH 2 CF 3 ;

(b) —CH 2 -phenyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8b , —SH, —NR 9 R 10 or —C 1-3 alkyl,

(c) —C 3-6 cycloalkyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8b , —SH, —NR 9 R 10 or —C 1-3 alkyl,

(d) phenyl or naphthyl, each unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8b , —SH, —NR 9 R 10 or —C 1-3 alkyl,

(e) —CH 2 CH 2 OCH 3 , —CH 2 CH 2 CH 2 OCH 3 , —CH 2 CH 2 SCH 3 , —CH 2 CH 2 CH 2 SCH 3 , —CH 2 CH 2 NHCH 3 , —CH 2 CH 2 CH 2 NHCH 3 ,

(f) pyridyl, unsubstituted or substituted with one to three substituents independently, wherein each substituent is independently from fluoro, chloro, bromo, —OR 8b , —SH, —NR 9 R 10 or —C 1-3 alkyl, or

(g) piperidinyl, pyrrolidinyl, tetrahydrofuranyl, or tetrahydropyranyl, each unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8b , —SH, —NR 9 R 10 or —C 1-3 alkyl.

6. The compound of claim 1 or a pharmaceutically acceptable salt thereof, wherein R 3 is:

(a) —C 1-8 alkyl, —CH 2 CH 2 OH, —CH 2 CH 2 CH 2 OH, —CH 2 CH 2 SH, —CH 2 CH 2 CH 2 SH, —CH 2 CH 2 NH 2 , —CH 2 CH 2 CH 2 NH 2 , —CH 2 CF 2 CH 3 or —CH 2 CH 2 CF 3 ;

(b) —CH 2 -phenyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8a , —SH, —NNR 6 R 7 or —C 1-3 alkyl, or

(c) —C 3-6 cycloalkyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8a , —SH, —NR 6 R 7 or —C 1-3 alkyl;

and R 4 is:

(a) —C 1-8 alkyl, —CH 2 CH 2 OH, —CH 2 CH 2 CH 2 OH, —CH 2 CH 2 SH, —CH 2 CH 2 CH 2 SH, —CH 2 CH 2 NH 2 , —CH 2 CH 2 CH 2 NH 2 , —CH 2 CF 2 CH 3 or —CH 2 CH 2 CF 3 ;

(b) —CH 2 -phenyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8b , —SH, —NR 9 R 10 or —C 1-3 alkyl, or

(c) —C 3-6 cycloalkyl, unsubstituted or substituted with one to three substituents, wherein each substituent is independently fluoro, chloro, bromo, —OR 8b , —SH, —NR 9 R 10 or —C 1-3 alkyl.

7. The compound of claim 2 , or a pharmaceutically acceptable salt thereof, wherein:

R 3 is —CN, unsubstituted or substituted phenyl, —C(O)OR 5b or —C(O)—N(R 6a )(R 6b ); and

R 4 is —H, —CN, unsubstituted or substituted phenyl, —C(O)OR 5c or —C(O)—N(R 6c )(R 6d ).

8. The compound of claim 7 , or a pharmaceutically acceptable salt thereof, wherein:

R 5a , R 5b and R 5c are each independently —C 1-10 alkyl unsubstituted or substituted with one to three substituents, wherein each substituent is independently selected from fluoro, chloro, bromo, —CN, —CF 3 , —NR 7a R 7b , —OR 8a , —SH, —C 3-6 cycloalkyl or spiro-C 3-6 cycloalkyl; and

R 6a , R 6b , R 6c and R 6d are each —C 1-6 alkyl.

9. The compound of claim 7 , or a pharmaceutically acceptable salt thereof, wherein R 5a , R 5b and R 5c are each —C 1-6 alkyl.

10. The compound of claim 1 or a pharmaceutically acceptable salt thereof, wherein:

R 1 and R 2 are both methyl,

R 3 is —CN, phenyl, —C(O)OR 5b or —C(O)—N(R 6a )(R 6b );

R 4 is —H, —CN, phenyl, —C(O)OR 5c or —C(O)—N(R 6c )(R 6d );

each of R 5a , R 5b and R 5c is —C 1-6 alkyl; and

each of R 6a , R 6b , R 6c and R 6d is —C 1-6 alkyl.

11. The compound of claim 1 that is:

Propyl 2-((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yloxy)methyl)(1-cyano-2-isopropoxy-2-oxoethyl)phosphorylamino)-2-methylpropanoate;

Diisopropyl 2-((R)—((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)((2-methyl-1-oxo-1-propoxypropan-2-yl)amino)phosphoryl)malonate;

Diisopropyl 2-((R)—((((S)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)((2-methyl-1-oxo-1-propoxypropan-2-yl)amino)phosphoryl)malonate;

Propyl 2-(((R)—((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(2-isopropoxy-2-oxoethyl)phosphoryl)amino)-2-methylpropanoate;

Propyl 2-(((R)—((((S)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(2-isopropoxy-2-oxoethyl)phosphoryl)amino)-2-methylpropanoate;

Propyl 2-((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yloxy)methyl)(cyanomethyl)phosphorylamino)-2-methylpropanoate;

Propyl 2-((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(2-isopropoxy-2-oxo-1-phenylethyl)phosphorylamino)-2-methylpropanoate;

Propyl 2-(((R)—((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(dicyanomethyl)phosphoryl)amino)-2-methylpropanoate;

Propyl 2-(((R)—((((S)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(dicyanomethyl)phosphoryl)amino)-2-methylpropanoate;

Propyl 2-(((R)—((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(2-(diethylamino)-2-oxoethyl)phosphoryl)amino)-2-methylpropanoate;

propyl 2-(((R)—((((S)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(2-(diethylamino)-2-oxoethyl)phosphoryl)amino)-2-methylpropanoate;

Propyl 2-((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(2-tert-butoxy-2-oxoethyl)phosphorylamino)-2-methylpropanoate;

Propyl 2-((((R)-1-(6-amino-9H-purin-9-yl)propan-2-yloxy)methyl)(benzyl)phosphorylamino)-2-methylpropanoate;

or a pharmaceutically acceptable salt thereof.

12. A pharmaceutical composition comprising an effective amount of the compound according to any one of claim 1 , or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

13. The pharmaceutical composition of claim 12 further comprising an effective amount of one or more additional HIV antiviral agents selected from HIV protease inhibitors, HIV integrase inhibitors, non-nucleoside HIV reverse transcriptase inhibitors, nucleoside HIV reverse transcriptase inhibitors, HIV fusion inhibitors and HIV entry inhibitors.

14. The pharmaceutical composition of claim 12 further comprising an effective amount of one or more additional HIV antiviral agents selected from: abacavir, abacavir sulfate, abacavir+lamivudine, abacavir+lamivudine+zidovudine, amprenavir, atazanavir, atazanavir sulfate, AZT, capravirine, darunavir, dideoxycytidine, dideoxyinosine, delavirdine, delavirdine mesylate, dolutegravir, doravirine, efavirenz, 4′-ethynyl-2-fluoro-2′-deoxyadenosine, elvitegravir, emtricitabine, emivirine, enfuvirtide, etravirine, fosamprenavir calcium, indinavir, indinavir sulfate, lamivudine, lamivudine+zidovudine, lopinavir, lopinavir+ritonavir, maraviroc, nelfinavir, nelfinavir mesylate, nevirapine, PPL-100, raltegravir, rilpivirine, ritonavir, saquinavir, saquinavir mesylate, stavudine, tipranavir, or vicriviroc.

15. A method for the treatment of an infection by HIV in a subject in need thereof which comprises administering to the subject an effective amount of the compound according to claim 1 , or a pharmaceutically acceptable salt thereof.

16. The method of claim 15 further comprising administering to the subject an effective amount of one or more additional HIV antiviral agents selected from HIV protease inhibitors, HIV integrase inhibitors, non-nucleoside HIV reverse transcriptase inhibitors, nucleoside HIV reverse transcriptase inhibitors, HIV fusion inhibitors and HIV entry inhibitors.

17. The method of claim 15 further comprising administering to the subject an effective amount of one or more additional HIV antiviral agents selected from: abacavir, abacavir sulfate, abacavir+lamivudine, abacavir+lamivudine+zidovudine, amprenavir, atazanavir, atazanavir sulfate, AZT, capravirine, darunavir, dideoxycytidine, dideoxyinosine, delavirdine, delavirdine mesylate, dolutegravir, doravirine, efavirenz, 4′-ethynyl-2-fluoro-2′-deoxyadenosine, elvitegravir, emtricitabine, emivirine, enfuvirtide, etravirine, fosamprenavir calcium, indinavir, indinavir sulfate, lamivudine, lamivudine+zidovudine, lopinavir, lopinavir+ritonavir, maraviroc, nelfinavir, nelfinavir mesylate, nevirapine, PPL-100, raltegravir, rilpivirine, ritonavir, saquinavir, saquinavir mesylate, stavudine, tipranavir, or vicriviroc.

18. The method of claim 15 wherein the subject is human.