Dihydroxypyridopyrazine-1,6-dione compounds useful as HIV integrase inhibitors

1. A compound of Formula (I), or a pharmaceutically acceptable salt thereof:

wherein

R 1 is —C 1-4 alkyl mono-substituted with aryl; wherein the aryl is optionally substituted with from 1 to 4 substituents each of which is independently

(1) —C 1-4 alkyl, optionally mono-substituted with —OH, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, —CN, —N(R a R b ), —C(═O)N(R a R b ), —C(═O)R a , —CO 2 R c , —S(O) n R c , —SO 2 N(R a R b ), —N(R a )C(═O)R b , —N(R a )CO 2 R c , —N(R a )SO 2 R c , —N(R a )SO 2 N(R a R b ), —OC(═O)N(R a R b ), or —N(R a )C(═O)N(R a R b ),

(2) —O—C 1-4 alkyl, optionally mono-substituted with —OH, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, —S(O) n R c , —N(R a )—CO 2 R c , —C(═O)N(R a R b ), —SO 2 N(R a R b ), —N(R a )C(═O)R b , —N(R a )CO 2 R c , —N(R a )SO 2 R c , —N(R a )SO 2 N(R a R b ), —OC(═O)N(R a R b ), or —N(R a )C(═O)N(R a R b ),

(3) —C 1-4 haloalkyl,

(4) —O—C 1-4 haloalkyl,

(5) —OH,

(6) halo,

(7) —CN,

(8) —NO 2 ,

(9) —N(R a R b ),

(10) —SR c ,

(11) —S(═O)R c ,

(12) —SO 2 R 2 ,

(13) —N(R a )SO 2 R c ,

(14) —SO 2 N(R a R b ),

(15) —N(R a )C(═O)R b ,

(16) —N(R a )CO 2 R c , or

(17) phenyl;

R 2 is —H or —C 1-6 alkyl;

R 3 is —H, —C 1-6 alkyl, —C 1-6 haloalkyl, or —C 1-6 alkyl substituted with one of —OH, —O—C 1-6 alkyl, —O—C 1-6 haloalkyl, —CN, —NO 2 , —N(R a R b ), —C(═O)N(R a R b ), —C(═O)R a , —CO 2 R c , —S(O) n R c , —SO 2 N(R a R b ), —N(R a )C(═O)R b , —N(R a )CO 2 R c , —N(R a )SO 2 R c , —N(R a )SO 2 N(R a R b ), —OC(═O)N(R a R b ), or —N(R a )C(═O)N(R a R b );

R 4 is:

(1) —H,

(2) —C 1-6 alkyl optionally substituted with one of —OH, —O—C 1-6 alkyl, —O—C 1-6 haloalkyl, —CN, —NO 2 , —N(R a R b ), —C(═O)N(R a R b ), —C(═O)R a , —CO 2 R c , —S(O) n R c , —SO 2 N(R a R b ), —N(R a )—C(R b )═O, —N(R a )SO 2 R c , —N(R a )SO 2 N(R a R b ), —OC(═O)N(R a R b ), —N(R a )C(═O)N(R a R b ), —O—C 1-6 alkyl-C(═O)N(R a R b ), —S—C 1-6 alkyl—C(═O)N(R a R b ), —N(R a )—C 1-6 alkyl-C(═O)N(R a R b ), or —N(SO 2 R c )—C 1-6 alkyl-C(═O)N(R a R b ),

(3) —C 1-6 haloalkyl,

(4) —C(═O)R a ,

(5) —CO 2 R c ,

(6) —C(═O)N(R a R b ),

(7) —SO 2 N(R a R b ),

(8) —C 2-6 alkenyl,

(9) —C 2-6 alkenyl-C(═O)—N(R a ) 2 ,

(10) —C 2-5 alkynyl,

(11) —C 2-5 alkynyl-CH 2 N(R a ) 2 ,

(12) —C 2-5 alkynyl-CH 2 OR a ,

(13) —C 2-5 alkynyl-CH 2 S(O) n R c , or

(14) —R k ,

(15) —C 1-6 alkyl substituted with R k ,

(16) —C 1-6 haloalkyl substituted with R k ,

(17) —C 1-6 alkyl-O—R k ,

(18) —C 1-6 alkyl-O—C 1-6 alkyl-R k ,

(19) —C 1-6 alkyl-S(O) n —R k ,

(20) —C 1-6 alkyl-S(O) n —C 1-6 alkyl—R k ,

(21) —C 1-6 alkyl-N(R a )—R k ,

(22) —C 1-6 alkyl-N(R a )—C 1-6 alkyl-R k ,

(23) —C 1-6 alkyl-N(R a )—C 1-6 alkyl-OR k , with the proviso that the —N(R a )— moiety and the —OR k moiety are not both attached to the same carbon of the —C 1-6 alkyl-moiety,

(24) —C 1-6 alkyl-C(═O)—R k ,

(25) —C 1-6 alkyl-C(═O)N(R a )—R k ,

(26) —C 1-6 alkyl-N(R a )C(═O)—R k ,

(27) —C 1-6 alkyl-C(═O)N(R a )—C 1-6 alkyl-R k , or

(28) —C 1-6 alkyl-N(R a )—C 0-6 alkyl-S(O) n R k ;

wherein R k is

(i) aryl, which is optionally substituted with from 1 to 5 substituents each of which is independently —C 1-6 alkyl, —C 1-6 alkyl-OH, —C 1-6 alkyl-O—C 1-6 alkyl, —C 1-6 alkyl-O—C 1-6 haloalkyl, —C 1-6 alkyl-N(R a R b ), —C 1-6 alkyl-C(═O)N(R a R b ), —C 1-6 alkyl-C(═O)R a , —C 1-6 alkyl-CO 2 R c , —C 1-6 alkyl-S(O) n R c , —O—C 1-6 alkyl, —C 1-6 haloalkyl, —O—C 1-6 haloalkyl, —OH, halo, —N(R a R b ), —C(═O)N(R a R b ), —C(═O)R a , —CO 2 R c , —S(O) n R c , or —SO 2 N(R a R b );

(ii) a 4- to 7-membered saturated or mono-unsaturated heterocyclic ring containing at least one carbon atom and from 1 to 4 heteroatoms independently selected from N, O and S, wherein the heterocyclic ring is:

(a) optionally substituted with from 1 to 5 substituents each of which is independently halogen, —C 1-6 alkyl, —C 1-6 haloalkyl, —O—C 1-6 alkyl, —O—C 1-6 haloalkyl, or oxo; and

(b) optionally mono-substituted with aryl or HetA;

wherein HetA is a 5- or 6-membered heteroaromatic ring containing from 1 to 4 heteroatoms independently selected from N, O and S, wherein the heteroaromatic ring is optionally fused with a benzene ring, and HetA is optionally substituted with from 1 to 4 substituents each of which is independently —C 1-6 alkyl, —C 1-6 haloalkyl, —O—C 1-6 alkyl, —O—C 1-6 haloalkyl, or oxo; or

(iii) a 5- or 6-membered heteroaromatic ring containing from 1 to 4 heteroatoms independently selected from N, O and S, wherein the heteroaromatic ring is optionally substituted with from optionally substituted with from 1 to 4 substituents each of which is independently —C 1-6 alkyl, —C 1-6 haloalkyl, —O—C 1-6 alkyl, —O—C 1-6 haloalkyl, or oxo;

or alternatively R 3 and R 4 are joined together to form C 5-8 cycloalkyl or a 5- to 7-membered saturated heterocyclic ring containing from 1 to 4 heteroatoms independently selected from N, O and S; wherein

the cycloalkyl is optionally substituted with from 1 to 3 substituents each of which is independently halo, —C 1-6 alkyl, or —O—C 1-6 alkyl; and

the heterocyclic ring is optionally substituted with from 1 to 4 substituents each of which is independently —C 1-6 alkyl, —C 1-6 haloalkyl, —O—C 1-6 alkyl, —O—C 1-6 haloalkyl, or oxo;

R 5 is:

(1) —H,

(2) —C 1-6 alkyl,

(3) —C 1-6 alkyl-N(R a R b ),

(4) —C 1-6 alkyl-C(═O)N(R a R b ),

(5) —C 1-6 alkyl-C(═O)R a ,

(6) —C 1-6 alkyl-CO 2 R c ,

(7) —C 1-6 alkyl-SR c ,

(8) —C 1-6 alkyl-S(═O)R c ,

(9) —C 1-6 alkyl-SO 2 R c ,

(10) —C 1-6 alkyl-SO 2 N(R a R b )

(11) —C 1-6 haloalkyl,

(12) —O—C 1-6 alkyl,

(13) —O—C 1-6 haloalkyl,

(14) halo,

(15) —CN,

(16) —C(═O)R a ,

(17) —CO 2 R c ,

(18) —SR c ,

(19) —S(═O)R c ,

(20) —SO 2 R c ,

(21) —N(R a R b ),

(22) —C(═O)N(R a R b ), or

(23) —SO 2 N(R a R b );

(24) aryl

(25) —C 1-6 alkyl-aryl

(26) HetB,

(27) —C 1-6 alkyl-HetB,

(28) HetC, or

(29) —C 1-6 alkyl-HetC,

wherein

HetB is a 5- or 6-membered saturated or mono-unsaturated ring containing from 1 to 4 heteroatoms independently selected from N, O and S, wherein the ring is optionally substituted with from 1 to 5 substituents each of which is independently halogen, —C 1-6 alkyl, —C 1-6 haloalkyl, —O—C 1-6 alkyl, —O—C 1-6 haloalkyl, oxo, —C(═O)—C 1-6 alkyl, —C(═O)—C 1-6 haloalkyl, or —C 1-6 alkyl—C 3-8 cycloalkyl; and

HetC is a 5- or 6-membered heteroaromatic ring containing from 1 to 4 heteroatoms independently selected from N, O and S, wherein the heteroaromatic ring is optionally substituted with from 1 to 4 substituents each of which is independently —C 1-6 alkyl, —C 1-6 haloalkyl, —O—C 1-6 alkyl, —O—C 1-6 haloalkyl, or oxo;

each aryl is independently phenyl or naphthyl;

each R a and R b is independently —H or —C 1-6 alkyl;

each R c is independently a —C 1-6 alkyl;

R d is a —C 1-6 alkyl, allyl, or benzyl; and

each n is independently an integer equal to 0, 1 or 2.

2. The compound according to claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 1 is —(CH 2 ) 1-4 -phenyl, wherein the phenyl is optionally substituted with from 1 to 3 substituents each of which is independently

(1) —C 1-4 alkyl, optionally mono-substituted with —OH, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, —CN, —N(R a R b ), —C(═O)N(R a R b ), —C(═O)R a , —CO 2 R c , —S(O) n R c , or —SO 2 N(R a R b ),

(2) —O—C 1-4 alkyl,

(3) —C 1-4 haloalkyl,

(4) —O—C 1-4 haloalkyl,

(5) —OH,

(6) halo,

(7) —CN,

(8) —NO 2 ,

(9) —N(R a R b ),

(10) —SR c ,

(11) —S(═O)R c ,

(12) —SO 2 R c ,

(13) —N(R a )SO 2 R c ,

(14) —SO 2 N(R a R b ),

(15) —N(R a )C(═O)R b ,

(16) —N(R a )CO 2 R c , or

(17) phenyl.

3. The compound according to claim 2 , or a pharmaceutically acceptable salt thereof, wherein R 1 is:

wherein X 1 and X 2 are each independently

(1) —H,

(2) methyl,

(3) ethyl,

(4) methoxy,

(5) ethoxy,

(6) —CF 3 ,

(7) fluoro,

(8) bromo,

(9) chloro,

(10) —CN,

(11) —S—CH 3 , or

(12) phenyl.

4. The compound according to claim 3 , or a pharmaceutically acceptable salt thereof, wherein R 1 is 4-fluorobenzyl.

5. The compound according to claim 1 , or a pharmaceutically acceptable salt thereof, wherein

R 2 is —H or —C 1-4 alkyl;

R 3 is —H or —C 1-4 alkyl; and

R 4 is:

(1) —H,

(2) —C 1-4 alkyl optionally substituted with one of —OH, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, —CN, —N(R a R b ), —C(═O)N(R a R b ), —C(═O)R a , —CO 2 R c , —S(O) n R c , —SO 2 N(R a R b ), —N(R a )—C(R b )═O, —N(R a )SO 2 R b , or —N(R a )SO 2 N(R a R b ),

(3) —C(═O)N(R a R b ),

(4) —R k ,

(5) —C 1-4 alkyl substituted with R k ,

(6) —C 1-4 alkyl-O—R k , or

(7) —C 1-4 alkyl-O—C 1-4 alkyl-R k .

6. The compound according to claim 1 , or a pharmaceutically acceptable salt thereof, wherein R 5 is:

(1) —H,

(2) —C 1-4 alkyl,

(3) —C 1-4 alkyl-N(R a R b ),

(4) —C 1-4 alkyl-C(═O)N(R a R b ),

(5) —C 1-4 alkyl-SO 2 N(R a R b )

(6) —C 1-4 haloalkyl,

(7) halo,

(8) —CN,

(9) aryl

(10) —C 1-4 alkyl-aryl

(11) HetB,

(12) —C 1-4 alkyl-HetB,

(13) HetC, or

(14) —C 1-4 alkyl-HetC,

wherein

HetB is a 5- or 6-membered saturated ring containing a total of from 1 to 4 heteroatoms independently selected from 1 to 4 N atoms, from 0 to 2 O atoms, and from 0 to 2 S atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently halogen, —C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, oxo, —C(═O)—C 1-4 alkyl, —C(═O)—C 1-4 haloalkyl, or —C 1-4 alkyl-C 3-6 cycloalkyl; and

HetC is a 5- or 6-membered heteroaromatic ring containing a total of from 1 to 4 heteroatoms independently selected from 1 to 4 N atoms, from 0 to 2 O atoms, and from 0 to 2 S atoms, wherein the heteroaromatic ring is optionally substituted with from 1 to 3 substituents each of which is independently —C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, or oxo.

7. The compound according to claim 6 , or a pharmaceutically acceptable salt thereof, wherein R 5 is:

(1) —H,

(2) —C 1-4 alkyl,

(3) —C 1-4 alkyl-N(R a R b ),

(4) halo,

(5) —CN, or

(6) —C 1-4 alkyl-HetB;

wherein

HetB is a 5- or 6-membered saturated ring containing 1 or 2 N atoms and carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently halogen, —C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, oxo, —C(═O)—C 1-4 alkyl, —C(═O)—C 1-4 haloalkyl, or —C 1-4 alkyl-C 3-6 cycloalkyl.

8. A compound of Formula (II), or a pharmaceutically acceptable salt thereof:

wherein:

X 1′ and X 2′ are each independently:

(1) —H,

(2) C 1-4 alkyl,

(2) —O—C 1-4 alkyl,

(3) —C 1-4 haloalkyl,

(4) —O—C 1-4 haloalkyl,

(5) halo,

(6) —CN,

(7) —S—C 1-4 alkyl, or

(8) phenyl;

R 2′ is —H or —C 1-4 alkyl;

R 3′ is —H or —C 1-4 alkyl;

R 4′ is:

(1) —H,

(2) —C 1-4 alkyl optionally substituted with one of —OH, —N(R a′ R b′ ), or —C(═O)N(R a′ R b′ ),

(4) —(CH 2 ) 1-3 —R k′ ,

(5) —(CH 2 ) 1-3 —O—R k′ , or

(6) —(CH 2 ) 1-3 —O—(CH 2 ) 1-3 —R k′ ;

wherein R k′ is:

(i) phenyl, which is optionally substituted with from 1 to 3 substituents each of which is independently —C 1-4 alkyl, —O—C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 haloalkyl, or halo; or

(ii) HetD, wherein HetD is a 5- or 6-membered saturated ring containing 1 or 2 N atoms, 0 or 1 S atoms, and a balance of carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently halo, —C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, or oxo;

R 5′ is:

(1) —H,

(2) —C 1-4 alkyl,

(3) —C 1-4 alkyl-N(R a′ R b′ ),

(4) halo,

(5) —CN, or

(6) —(CH 2 ) 1-3 -HetB;

wherein

HetB is a 5- or 6-membered saturated ring containing 1 or 2 N atoms, zero or 1 O atom, zero or 1 S atom, and a balance of carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently halogen, —C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 , alkyl, —O—C 1-4 haloalkyl, oxo, —C(═O)—C 1-4 alkyl, —C(═O)—C 1-4 haloalkyl, or —C 1-4 alkyl-C 3-6 cycloalkyl;

R 6′ is —H or methyl;

each R a′ and R b′ is independently —H or —C 1-4 alkyl; and

R d′ is —C 1-4 alkyl, allyl, or benzyl.

9. A compound according to claim 8 , or a pharmaceutically acceptable salt thereof, wherein:

wherein X 1′ and X 2′ are each independently:

(1) —H,

(2) methyl,

(2) —OCH 3 ,

(3) —CF 3 ,

(4) —O—CF 3 ,

(5) chloro,

(6) fluoro,

(7) bromo;

(6) —CN,

(7) —S—CH 3 , or

(8) phenyl;

R 2′ is —H or methyl;

R 3′ is —H or methyl;

R 4′ is:

(1) —H,

(2) methyl,

(3) —CH 2 OH,

(3) —C(═O)N(CH 3 ) 2 ,

(4) —CH 2 —R k′ , or

(5) —CH 2 —O—CH 2 R k′ ;

wherein R k′ is:

(i) phenyl, which is optionally substituted with from 1 to 3 substituents each of which is independently —CH 3 , —OCH 3 , —CF 3 , —OCF 3 , chloro, bromo or fluoro; or

(ii) HetD, wherein HetD is a 5- or 6-membered saturated ring containing 1 or 2 N atoms, 0 or 1 S atoms, and a balance of carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently chloro, bromo, fluoro, —CH 3 , —CF 3 , —OCH 3 , —OCF 3 , or oxo;

R 5′ is:

(1) —H,

(2) methyl,

(3) —(CH 2 ) 1-2 —N(CH 3 ) 2 ,

(4) fluoro,

(5) bromo,

(6) iodo,

(7) —CN, or

(8) —CH 2 -HetB;

wherein

HetB is a 5- or 6-membered saturated ring containing 1 or 2 N atoms, zero or 1 O atom, zero or 1 S atom, and a balance of carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently chloro, bromo, fluoro, —CH 3 , —CF 3 , —OCH 3 , —OCF 3 , oxo, —C(═O)—CH 3 , —C(═O)—CF 3 , or —CH 2 -cyclopropyl; and

R6′ is —H or methyl.

10. The compound according to claim 8 , which is a compound of Formula (IIa), or a pharmaceutically acceptable salt thereof:

wherein:

X 1′ and X 2′ are each independently:

(1) —H,

(2) C 1-4 alkyl,

(2) —O—C 1-4 alkyl,

(3) —C 1-4 haloalkyl,

(4) —O—C 1-4 haloalkyl, or

(5) halo;

R 2′ is —H or —C 1-4 alkyl;

R 3′ is —H or —C 1-4 alkyl;

R 4′ is:

(1) —H,

(2) —C 1-4 alkyl optionally substituted with one of —OH, —N(R a′ R b′ ), or —C(═O)N(R a′ R b′ ),

(3) —C(═O)N(R a′ R b′ ),

(4) —(CH 2 ) 1-3 —R k′ ,

(5) —(CH 2 ) 1-3 —O—R k′ , or

(6) —(CH 2 ) 1-3 —O—(CH 2 ) 1-3 —R k′ ;

wherein R k′ is:

(i) phenyl, which is optionally substituted with from 1 to 3 substituents each of which is independently —C 1-4 alkyl, —O—C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 haloalkyl, or halo; or

(ii) HetD, wherein HetD is a 5- or 6-membered saturated ring containing 1 or 2 N atoms, 0 or 1 S atoms, and a balance of carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently halo, —C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, or oxo;

R 5′ is:

(1) —H,

(2) —C 1-4 alkyl,

(3) —C 1-4 alkyl-N(R a′ R b′ ),

(4) halo,

(5) —CN, or

(6) —(CH 2 ) 1-3 -HetB;

wherein

HetB is a 5- or 6-membered saturated ring containing 1 or 2 N atoms and carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently halogen, —C 1-4 alkyl, —C 1-4 haloalkyl, —O—C 1-4 alkyl, —O—C 1-4 haloalkyl, or oxo; and

each R a′ and R b′ is independently —H or —C 1-4 alkyl.

11. The compound according to claim 8 , which is a compound of Formula (III), or a pharmaceutically acceptable salt thereof:

wherein:

X 1′ and X 2′ are each independently —H or halo.

12. The compound according to claim 11 , or a pharmaceutically acceptable salt thereof,

wherein X 1′ and X 2′ are each independently —H, fluoro, chloro, or bromo;

R 2′ is —H or methyl;

R 3′ is —H or methyl;

R 4′ is:

(1) —H,

(2) methyl,

(3) —CH 2 OH,

(3) —C(═O)N(CH 3 ) 2 ,

(4) —CH 2 —R k′ , or

(5) —CH 2 —R k′ ;

wherein R k′ is:

(i) phenyl, which is optionally substituted with from 1 to 3 substituents each of which is independently —CH 3 , —OCH 3 , —CF 3 , —OCF 3 , chloro, bromo or fluoro; or

(ii) HetD, wherein HetD is a 5- or 6-membered saturated ring containing 1 or 2 N atoms, 0 or 1 S atoms, and a balance of carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently chloro, bromo, fluoro, —CH 3 , —CF 3 , —OCH 3 , —OCF 3 , or oxo; and

R 5′ is:

(1) —H,

(2) methyl,

(3) —(CH 2 ) 1-2 —N(CH 3 ) 2 ,

(4) fluoro,

(5) bromo,

(6) iodo,

(7) —CN, or

(8) —CH 2 -HetB;

wherein

HetB is a 5- or 6-membered saturated ring containing 1 or 2 N atoms, zero or 1 O atom, zero or 1 S atom, and a balance of carbon atoms, wherein the saturated ring is optionally substituted with from 1 to 4 substituents each of which is independently chloro, bromo, fluoro, —CH 3 , —CF 3 , —OCH 3 , —OCF 3 , oxo, —C(═O)—CH 3 , —C(═O)—CF 3 , or —CH 2 -cyclopropyl.

13. The compound according to claim 12 , or a pharmaceutically acceptable salt thereof, wherein X 1′ is fluoro and X2′ is —H.

14. A compound selected from the group consisting of:

2-benzyl-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-7-methyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-7-bromo-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-7-iodo-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(3-chlorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-chlorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione

2-(3,4-dichlorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(3,4-difluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione

2-(3-chloro-4-fluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione

2-(4-fluorobenzyl)-8,9-dihydroxy-7-(piperidin-1-ylmethyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(3-chloro-4-fluorobenzyl)-8,9-dihydroxy-7-(piperidin-1-ylmethyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-7-[(dimethylamino)methyl]-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-2H-pyrido[1,2-a]pyrazine-1,6-dione

2-benzyl-8,9-dihydroxy-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-4-methyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione

2-(4-fluorobenzyl)-8,9-dihydroxy-4,4-dimethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-3-methyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-1,6-dioxo-1,3,4,6-tetrahydro-2H-pyrido[1,2-a]-pyrazine-7-carbonitrile;

2-(4-fluorobenzyl)-8,9-dihydroxy-7-[(4-methyl-3-oxopiperazin-1-yl)methyl]-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-7-[(3-oxopiperazin-1-yl)methyl]-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

4-[(benzyloxy)methyl]-2-(4-fluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

4-(hydroxymethyl-2-(4-flurobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

4-[(1,1-dioxido-1,2-thiazinan-2-yl)methyl]-2-(4-flurobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

7-[(1-acetylpiperidin-4-yl)methyl]-2-(4-fluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(4-fluorobenzyl)-8,9-dihydroxy-7-{[1-(trifluoroacetyl)piperidin-4-yl]methyl}-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

7-{[1-(cyclopropylmethyl)piperidin-3-yl]methyl}-2-(4-fluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

7-[(1-acetylpiperidin-3-yl)methyl]-2-(4-fluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

7-[(1-acetylpiperidin-2-yl)methyl]-2-(4-fluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

7-{[1-(cyclopropylmethyl)piperidin-2-yl]methyl}-2-(4-fluorobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

2-(3-cyanobenzyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione

2-(biphenyl-3-ylmethyl)-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione

2-[1-(4-fluorophenyl)ethyl]-8,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,6-dione;

and pharmaceutically acceptable salts thereof.

15. A pharmaceutical composition comprising a compound according to claim 1 , or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

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

17. A combination useful for treating infection by HIV, or for treating AIDS, which is a therapeutically effective amount of a compound according to claim 1 , or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of an HIV infection/AIDS antiviral agent selected from the group consisting of HIV protease inhibitors, non-nucleoside HIV reverse transcriptase inhibitors and nucleoside HIV reverse transcriptase inhibitors.