Nitrogen-containing fused ring compound and use thereof as HIV integrase inhibitor

Abstract

The present invention relates to a nitrogen-containing fused ring compound represented by the following formula [I] wherein each symbol is as defined in the specification, or a pharmaceutically acceptable salt thereof, and an anti-HIV agent containing such compound. The compound of the present invention has an HIV integrase inhibitory activity, and is useful as an agent for the prophylaxis or treatment of AIDS, or as an anti-HIV agent. In addition, by the combined use with other anti-HIV agents such as a protease inhibitor, a reverse transcriptase inhibitor and the like, it can be a more effective anti-HIV agent. Becuae it shows integrase-specific high inhibitory activity, the compound can be a pharmaceutical agent safe on human body, which causes only a fewer side effects.

1 . A nitrogen-containing fused ring compound represented by the following formula [I] or a pharmaceutically acceptable salt thereof:  
       
         
           
           
               
               
           
         
       
       wherein 
 R 1  is 
 (1) a C1-6 alkyl group optionally substituted by 1 to 3 substituent(s) selected from the following group A,  
 (2) a C2-6 alkenyl group optionally substituted by 1 to 3 substituent(s) selected from the following group A or  
 (3) a group represented by the formula  
                     
 
 wherein Z is 
 (1′) a bond,  
 (2′) a C1-6 alkylene,  
 (3′) a C2-6 alkenylene or  
 (4′) *-(CH 2 ) m —Q—(CH 2 ) n — 
 
 wherein Q is 
 (1″) —O—,  
 (2″) —NR 5 —
 wherein R 5  is a hydrogen atom or a C1-6 alkyl group,  
 
 (3″) —CO—,  
 (4″) —SO—,  
 (5″) —SO 2   −  or  
 (6″) **-CO—NR 6 —
 wherein R 6  is a hydrogen atom or a C1-6 alkyl group and ** shows the side to be bonded to (CH 2 ) m ,  
 
 
 m is 0 or an integer of 1 to 4,  
 n is 0 or an integer of 1 to 4 and  
 * shows the side to be bonded to a nitrogen atom of ring A,  
 and  
 ring D is  
 (1′) a C3-10 carbon ring group optionally substituted by 1 to 3 substituent(s) selected from the following group B or  
 (2′) a heterocyclic group optionally substituted by 1 to 3 substituent(s) selected from the following group B  
 wherein the heterocyclic group contains at least one hetero atom selected from nitrogen atom, oxygen atom and sulfur atom;  
 X is 
 (1) C(R x1 )(R x2 )-#,  
 (2) —C(R x1 )(R x2 )—C(R x3 )(R x4 )-#,  
 (3) —C(R x1 )(R x2 )—C(R x3 )(R x4 )—C(R x5 )(R x6 )-#,  
 (4) —C(R x7 )═C(R x 8)-#,  
 (5) —C(R x1 )(R x2 )—C(R x7 )═C(R x8 )-#,  
 (6) —C(R x7 )═C(R x8 )—C(R x1 )(R x2 )-#,  
 (7) —N═C(R x9 )-# or  
 (8) —C(R x10 )═N-# 
 wherein # shows the side to be bonded to Y 1  of ring B, R x1  to R x10  are each independently selected from the following group C, R x1  and R x2 , R x3  and R x4 , and R x5  and R x6  each independently optionally form a C3-8 cycloalkyl together with the adjacent carbon atom;  
                     
 
 of ring B is 
 (1) C═C(R y1 )—N(R y2 )  
 (2) N—C(R y1 )═N,  
 (3) N—C(R y1 )═C(R y2 )  
 (4) C═N—N(R y2 ) or  
 (5) N—N═C(R y3 ) 
 wherein R y1  to R y3  are each independently selected from the following group C,  
 
 
 when  
                     
  s N—C(R y1 )═C(R y2 ), ring B is optionally condensed with a benzene ring to form a fused ring represented by  
                     
 wherein R 4  is selected from the following group C; and R 2  is  
 (1) a hydrogen atom, 
 (2) a C1-6 alkyl group,  
 (3) a C6-14 aryl C1-6 alkyl group or  
 (4) −SO 2 R d1    
 
 wherein R d1  is a hydrogen atom, a C1-7 alkyl group optionally substituted by 1 to 3 substituent(s) selected from the following group A or a C6-14 aryl group:  
 group A: 
 (1) a halogen atom,  
 (2) a cyano group,  
 (3) —OR a1 ,  
 (4) —SR a1 ,  
 (5) —CO 2 R a1 ,  
 (6) —CONR a2 R a3 ,  
 (7) —COR a4 ,  
 (8) —SO 2 NR a2 R a3 ,  
 (9) —SO 2 R a4 ,  
 (10) a C6-14 aryloxy group,  
 (11) a C6-14 aryl C1-6 alkyloxycarbonyl group,  
 (12) a C1-6 alkylcarbonyloxy group optionally substituted by halogen atom(s),  
 (13) a C6-14 aryl group optionally substituted by 1 to 3 substituent(s) selected from the group consisting of a halogen atom, a C1-6 alkyl group, a C1-6 alkylsulfonyl group, a di(C1-6 alkyl) amino group and a C1-6 alkylcarbonylamino group and  
 (14) a heterocyclic group optionally substituted by a C1-6 alkyloxy group, wherein R a1 , R a2 , R a3  and R a4  are each independently a hydrogen atom or a C1-6 alkyl group;  
 
 group B: 
 (1) a halogen atom,  
 (2) a cyano group,  
 (3) a C1-6 alkyl group,  
 (4) a halo C1-6 alkyl group,  
 (5) —OR b1 ,  
 (6) —SR b1 ,  
 (7) —CO 2 R b1 ,  
 (8) —CONR b2 R b3 ,  
 (9) —COR b4 ,  
 (10) —SO 2 NR b2 R b3 ,  
 (11) —SO 2 R b4 ,  
 (12) a C6-14 aryloxy group,  
 (13) a C6-14 aryl C1-6 alkyloxycarbonyl group,  
 (14) a C6-14 aryl C1-6 alkyloxy group and  
 (15) —NR b5 COR b6 , 
 wherein R b1 , R b2 , R b3 , R b4 , R b5  and R b6  are each independently a hydrogen atom or a C1-6 alkyl group;  
 
 
 group C: 
 (1) a hydrogen atom,  
 (2) a C3-8 cycloalkyl C1-6 alkyl group,  
 (3) a cyano group,  
 (4) a halogen atom,  
 (5) a C1-7 alkyl group,  
 (6) a C2-6 alkenyl group,  
 (7) a C2-6 alkynyl group,  
 (8) a C6-14 aryl group,  
 (9) a heterocyclic group 
 wherein said heterocyclic group is a saturated or unsaturated 5-membered or 6-membered heteromonocycle containing at least one hetero atom selected from nitrogen atom, oxygen atom and sulfur atom, or a fused ring of such heterocycles, or a fused ring of a carbon ring selected from benzene, cyclopentane and cyclohexane and the above-defined heterocycle,  
 
 (10) a C1-6 alkyloxy group,  
 (11) a C6-14 aryl C1-6 alkyl group,  
 (12) a C6-14 aryl C1-6 alkyloxy group,  
 (13) —CO 2 R c1 ,  
 (14) —CONR c2 R c3 ,  
 (15) —COR c4 ,  
 (16) —SO 2 NR c2 R c3 ,  
 (17) a C6-14 arylcarbonyl group,  
 (18) —NR c4 R c5 ,  
 (19) —NR c6 COR c7 ,  
 (20) —NR c8 SO 2 R c9 ,  
 (21) —SR c10 ,  
 (22) —SOR c11    
 (23) —SO 2 R c12 ,  
 (24) —NR c13 CONR c14 R c15 ,  
 (25) —NR c16 CO 2 R c17  and,  
 (26) —NR c18 COCOR c19 ,  
 wherein R c1 , R c2 , R c3 , R c4 , R c5 , R c6 , R c7 , R c8 , R c9 , R c10 , R c11 , R c12 , R c13 , R c14 , R c15 , R c16 , R c17 , R c18  and R c19  are each independently  
 
 (1′) a hydrogen atom,  
 (2′) a C1-7 alkyl group optionally substituted by 1 to 3 substituent(s) selected from the above-mentioned group A,  
 (3′) a C6-14 aryl group optionally substituted by 1 to 3 substituent(s) selected from the above-mentioned group B,  
 (4′) a heterocyclic group optionally substituted by 1 to 3 substituent(s) selected from the above-mentioned group B or  
 (5′) a C3-8 cycloalkyl group,  
 wherein R c2  and R c3  optionally form, together with the adjacent nitrogen atom, a nitrogen-containing heterocycle optionally substituted by 1 to 3 substituent(s) selected from the above-mentioned group B;  
 the C1-7 alkyl group, C1-6 alkyl moiety, C2-6 alkenyl group and C2-6 alkynyl group of the above-mentioned group C are optionally substituted by 1 to 3 substituent(s) selected from the above-mentioned group A, or a heterocyclic group; and  
 the C6-14 aryl group, C6-14 aryl moiety and heterocyclic group of the above-mentioned group C are optionally substituted by 1 to 3 substituent(s) selected from the above-mentioned group B.  
 
     
     
         2 . The nitrogen-containing fused ring compound of  claim 1 , wherein  
       
         
           
           
               
               
           
         
       
       of ring B is C═C(R y1 )—N(R y2 ), N—C(R y1 )═N, N—C(R y1 )═C(R y2 ) or 
 C═N—N(R y2 ), wherein each symbol is as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.  
 
     
     
         3 . The nitrogen-containing fused ring compound of  claim 2 , which is represented by the following formula [I]-1, or a pharmaceutically acceptable salt thereof:  
       
         
           
           
               
               
           
         
       
       wherein each symbol is as defined in  claim 1 .  
     
     
         4 . The nitrogen-containing fused ring compound of  claim 2 , which is represented by the following formula [I]-2, or a pharmaceutically acceptable salt thereof:  
       
         
           
           
               
               
           
         
       
       X— wherein each symbol is as defined in  claim 1 .  
     
     
         5 . The nitrogen-containing fused ring compound of  claim 2 , which is represented by the following formula [I]-3, or a pharmaceutically acceptable salt thereof:  
       
         
           
           
               
               
           
         
       
       wherein each symbol is as defined in  claim 1 .  
     
     
         6 . The nitrogen-containing fused ring compound of  claim 2 , which is represented by the following formula [I]-4, or a pharmaceutically acceptable salt thereof:  
       
         
           
           
               
               
           
         
       
       wherein each symbol is as defined in  claim 1 .  
     
     
         7 . The nitrogen-containing fused ring compound of  claim 1  wherein X is —C(R x1 )(R x2 )—C(R x3 )(R x4 )-#, —(R x1 )(R x2 )—C(R x3 )(R x4 )—C(R x5 )(R x6 )-#, —C(R x7 )═C(R x8 )-#, —N═C(R x9 )-# or —C(R x10 )═N-# wherein each symbol is as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.  
     
     
         8 . The nitrogen-containing fused ring compound of  claim 7 , 
 wherein X is —C(R x1 )(R x2 )—C(R x3 )(R x4 )—C(R x5 )C(R x6 )-#, or —C(R x7 )═C(R X 8 )-# wherein each symbol is as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.    
     
     
         9 . The nitrogen-containing fused ring compound of  claim 8 , 
 wherein X is —C(R x1 )(R x2 )—C(R x3 )(R x4 )-# wherein each symbol is as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.    
     
     
         10 . The nitrogen-containing fused ring compound of  claim 8 , wherein X is —C(R x7 )═C(R x8 )-# wherein each symbol is as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.  
     
     
         11 . The nitrogen-containing fused ring compound of  claim 1 , wherein R 1  is a group represented by the formula  
       
         
           
           
               
               
           
         
         wherein Z is C1-6 alkylene or *-(CH 2 ) m —Q—(CH 2 ) n —, and other symbols are as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.  
       
     
     
         12 . The nitrogen-containing fused ring compound of  claim 11 , wherein Z is a C1-6 alkylene, or a pharmaceutically acceptable salt thereof.  
     
     
         13 . The nitrogen-containing fused ring compound of  claim 11 , wherein ring D is a C3-10 carbon ring group optionally substituted by 1 to 3 substituent(s) selected from group B, or a pharmaceutically acceptable salt thereof.  
     
     
         14 . The nitrogen-containing fused ring compound of  claim 1 , wherein R x1  to R x10  are each independently selected from the following groups and R x1  and R x2 , R x3  and R x4 , and R x5  and R x6  each independently optionally form, together with the adjacent carbon atom, a C3-8 cycloalkyl, or a pharmaceutically acceptable salt thereof: 
 a hydrogen atom,    a C3-8 cycloalkyl C1-6 alkyl group,    a cyano group,    a C1-7 alkyl group,    a C6-14 aryl group,    a C6-14 aryl C1-6 alkyl group,    —CO 2 R c1 ,    —CONR c2 R c3  and, —COR c4      wherein the above-mentioned C1-7 alkyl group and C1-6 alkyl moiety are optionally substituted by 1 to 3 substituent(s) selected from group A or a heterocyclic group, and other symbols are as defined in  claim 1 .    
     
     
         15 . The nitrogen-containing fused ring compound of  claim 14 , wherein R x1  to R x10  are each a hydrogen atom, or a pharmaceutically acceptable salt thereof.  
     
     
         16 . The nitrogen-containing fused ring compound of  claim 1 , wherein R y1  is selected from the following groups, or a pharmaceutically acceptable salt thereof: 
 a hydrogen atom,    a C1-7 alkyl group,    a C6-14 aryl group,    —CO 2 R c1 ,    —CONR c2 R c3 ,    —COR c4  and,    a C6-14 arylcarbonyl group    wherein the above-mentioned C1-7 alkyl group is optionally substituted by 1 to 3 substituent(s) selected from group A or a heterocyclic group, the above-mentioned C6-14 aryl group is optionally substituted by 1 to 3 substituent(s) selected from group B, and other symbols are as defined in  claim 1 .    
     
     
         17 . The nitrogen-containing fused ring compound of  claim 16 , wherein R y1  is a hydrogen atom, or a pharmaceutically acceptable salt thereof.  
     
     
         18 . The nitrogen-containing fused ring compound of  claim 1 , wherein R y2  is selected from the following groups, or a pharmaceutically acceptable salt thereof: 
 a hydrogen atom,    a halogen atom,    a C1-7 alkyl group    a C6-14 aryl group,    a heterocyclic group,    —CO 2 R c1 ,    —CONR c2 R c3 ,    —COR c4 ,    —NR c4 R c5 ,    —NR c6 COR c7 ,    —NR c8 SO 2 R c9 ,    —SR c10 ,    —SO 2 R c12      —NR c13 CONR c14 R c15 ,    —NR c16 CO 2 R c17  and,    —NR c18 COCOR c19      wherein the above-mentioned C1-7 alkyl group is optionally substituted by 1 to 3 substituent(s) selected from group A or a heterocyclic group, the above-mentioned C6-14 aryl group and heterocyclic group are optionally substituted by 1 to 3 substituent(s) selected from group B, and other symbols are as defined in  claim 1 .    
     
     
         19 . The nitrogen-containing fused ring compound of  claim 18 , wherein R y2  is a heterocyclic group optionally substituted by 1 to 3 substituent(s) selected from group B, or a pharmaceutically acceptable salt thereof.  
     
     
         20 . The nitrogen-containing fused ring compound of  claim 19 , wherein R y2  is a heterocyclic group optionally substituted by 1 to 3 substituent(s) selected from group B, which is bonded to Y 3  via a carbon atom, wherein at least one α-position of the carbon atom is a hetero atom selected from the group consisting of nitrogen atom, oxygen atom and sulfur atom, or a pharmaceutically acceptable salt thereof.  
     
     
         21 . The nitrogen-containing fused ring compound of  claim 18 , wherein R y2  is selected from —CO 2 R c1 , CONR c2 R C3  and —COR c4  wherein each symbol is as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.  
     
     
         22 . The nitrogen-containing fused ring compound of  claim 18 , wherein R y2  is selected from —NR c4 R c5 , —NR c6 COR c7 , —NR c8 SO 2 R c9 , —NR c13 CONR c14 R c15 , —NR c16 CO 2 R c17  and —NR c18 COCOR c19  wherein each symbol is as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.  
     
     
         23 . The nitrogen-containing fused ring compound of  claim 22 , wherein R y2  is selected from —NR c6 COR c7 , —NR c8 SO 2 R c9 , —NR c13 CONR c14 R c15 , —NR c16 CO 2 R c17  and —NR c18 COCOR c19  wherein each symbol is as defined in  claim 1 , or a pharmaceutically acceptable salt thereof.  
     
     
         24 . The nitrogen-containing fused ring compound of  claim 1 , wherein R 2  is a hydrogen atom, or a pharmaceutically acceptable salt thereof.  
     
     
         25 . The nitrogen-containing fused ring compound of  claim 1 , which is selected from the group consisting of 
 2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3,4-dichlorobenzyl)-10-hydroxy-2,3,4,5-tetrahydropyrido[1,2-a][1,4]diazepine-1,9-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-3-methyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4,4-dimethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-hydroxymethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carboxylic acid,    2-(3,4-dichlorobenzyl)-6-(2,2-dimethylpropionyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-3-methyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-4-isopropyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-[3-(2,6-dichlorophenyl) propyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-2H-pyrazino[1,2-c]pyrimidine-1,8-dione hydrochloride,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-methyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    4-benzyl-2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-phenyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    4-butyl-2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-isopropyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-3,3-dimethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-4-spiro-1′-cyclopentane-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-4-spiro-1′-cyclohexane-1,8-dione,    methyl 2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-4-carboxylate,    2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-4-carboxylic acid,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-methoxymethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N,N-dimethyl-2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carboxamide,    3-benzyl-2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    3-butyl-2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N,N-dimethyl-2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-4-carboxamide, 2-(3,4-dichlorobenzyl)-9-hydroxy-4-hydroxymethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-methoxymnethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-], 8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-methylsulfanylmethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-methanesulfonylmethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-(2-methanesulfonylethyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-(2-methylsulfanylethyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione, methyl 2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carboxylate,    6-acetyl-2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-isopropylsulfanylmethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-isopropylsulfanylmethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-isopropoxymethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-isobutoxymethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-(1-hydroxyethyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-phenoxymethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-fluorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-benzyl-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-chlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-isopropyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-isobutyryl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carbaldehyde,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-phenyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    9-hydroxy-2-(3-phenylpropyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chloro-2-fluorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    9-hydroxy-2-phenethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-(1-hydroxy-2-methylpropyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-isobutyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carboxamide,    N-methyl-2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carboxamide,    2-(4-chloro-3-fluorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    6-benzoyl-2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-propionyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-methyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N,N-diethyl-2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carboxamide,    N-isopropyl-N-methyl-2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carboxamide,    N-ethyl-N-methyl-2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-6-carboxamide,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(2-chlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,5-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    6-tert-butyl-2-(3,4-dichlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-(1-hydroxy-2,2-dimethylpropyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    3-benzyl-9-hydroxy-2-methyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-[3-(4-chlorophenyl)propyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-[3-(2-chlorophenyl)propyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-methyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-methoxybenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    9-hydroxy-2-methyl-3-phenethyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    [2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-6-yl]acetonitrile,    2-[3-(3-chlorophenyl)propyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    9-hydroxy-2-methyl-3-(3-phenyipropyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-isopropyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-[3-(3,4-dichlorophenyl)propyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-[3-(3,5-dichlorophenyl)propyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    benzyl[2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-6-yl]acetate,    benzyl 2-[2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-6-yl]-3-phenylpropionate,    2-(3,4-dichlorobenzyl)-9-hydroxy-6-(2-hydroxyethyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-propyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-4-ethyl-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-hydroxymethyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-isobutyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    methyl 2-(3,4-dichlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-4-carboxylate,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-[3-(2,3-dichlorophenyl)propyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-4-isopropyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    methyl 2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-4-carboxylate,    7-bromo-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-[3-(2-chloro-6-fluorophenyl)propyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-phenyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N,N-dimethyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-4-carboxamide,    2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-4-carboxylic acid,    3-(3-chlorobenzyl)-5-hydroxy-3H-pyrazino[1,2-a]quinoline-4,6-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-2H-pyrazino[1,2-c]pyrimidine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-4-carbaldehyde,    2-(3-chlorobenzyl)-9-hydroxy-4-hydroxymethyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-4-(1-hydroxyethyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-isopropyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    4-acetyl-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-8-hydroxy-6-methyl-2,3,4,6-tetrahydro-2,6-naphthyridine-1,7-dione,    2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-4-carbonitrile,    2-(3-chlorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrazino[1,2-c]pyrimnidine-1,8-dione,    7-bromo-2-(3-chlorobenzyl)-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-9-yl methanesulfonate,    7-bromo-2-(3-chlorobenzyl)-3,9-dihydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    3-(3-chlorobenzyl)-5-hydroxy-2,3-dihydro-1H-pyrazino[1,2-a]quinoline-4,6-dione,    2-(3-chlorobenzyl)-7-(3-chlorophenyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(4-chlorophenyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(2-chlorophenyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyridin-3-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyridin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(1-hydroxy-2,2-dimethylpropyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-4-cyclohexylmethyl-9-hydroxy-7-phenyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(furan-2-yl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3,4-dichlorobenzyl)-8-hydroxy-6-methyl-2,3,4,6-tetrahydro-2,6-naphthyridine-1,7-dione,    2-[3-(2-chloro-6-fluorophenyl)propyl]-8-hydroxy-6-methyl-2,3,4,6-tetrahydro-2,6-naphthyridine-1,7-dione,    6-(3-chlorobenzyl)-4-hydroxy-2-methyl-2,6,7,8-tetrahydropyrido[4,3-c]pyridazine-3,5-dione,    7-(benzofuran-2-yl)-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-]8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(2,2-dimethylpropyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(2-trifluoromethylphenyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(3-methoxyphenyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    7-bromo-2-(3-chlorobenzyl)-9-hydroxy-4-isopropyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(2-fluorophenyl)-9-hydroxy-2H pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-4-isopropyl-7-phenyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(2-methoxyphenyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(4-methoxyphenyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-ethyl-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(2,6-dimethylphenyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(3-hydroxyphenyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    7-benzoyl-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(2-ethylphenyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-(3-chlorophenyl)-9-hydroxy-4-isopropyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    7-benzyl-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(2-hydroxyphenyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-(4-hydroxyphenyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    8-hydroxy-6-methyl-2-(3-trifluoromethylbenzyl)-2,3,4,6-tetrahydro-2,6-naphthyridine-1,7-dione,    8-hydroxy-2-(3-methoxybenzyl)-6-methyl-2,3,4,6-tetrahydro-2,6-naphthyridine-1,7-dione,    6-(3-chlorobenzyl)-4-hydroxy-2-methyl-2,6-dihydropyrido[4,3-c]pyridazine-3,5-dione,    3-(3-chlorobenzyl)-5-hydroxy-3H-pyrido[2,1-f][1,2,4]triazine-4,6-dione,    methyl 2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxylate hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(1-methyl-1H-imidazol-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-isobutyryl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    isopropyl 2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxylate,    2-(4-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxylic acid hydrochloride,    N,N-dimethyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxylic acid isopropylamide,    N-methyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N,N-diethyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(4-bromobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-bromobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2,2-dimethylpropyl 2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxylate,    cyclohexyl 2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxylate,    7-amnino-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-4-methyl-2H-pyrido[1,2-d][1,2,4]triazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(4H-1,2,4-triazol-3-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetamide,    2-(4-chloro-2-methoxybenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chloro-2-methoxybenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-[2-(2-chlorophenoxy)ethyl]-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyrimidin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-propyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-butyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-isobutyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    methyl {[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carbonyl]amino}acetate,    N-ethyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-(2-methoxyethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-{[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carbonyl]amino) ethyl trifluoroacetate,    N-(2-hydroxyethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chloro-2-hydroxybenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-benzyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-(2,2,2-trifluoroethyl)-2-(3-chlorobenzyl)-9-hydraxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-butyl-N-methyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-(2-methoxyethyl)-N-methyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyrrolidine-1-carbonyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-(morpholine-4-carbonyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-chloro-3-methoxybenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride, methyl [2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetate,    2-(3-chlorobenzyl)-9-hydroxy-7-(1H-tetrazol-5-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-N-methylacetamide,2-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-N,N-dimethylacetamide,    [2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetic acid,    N-(2-hydroxypropyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    {[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carbonyl]amino}acetic acid,    N-dimethylcarbamoylmethyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-methylcarbamoylmethyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-phenyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(oxazol-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(3-hydroxypyrrolidine-1-carbonyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-(2-oxopropyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(9-hydroxy-1,8-dioxo-1,8-dihydro-pyrido[1,2-a]pyrazin-2-yl)-N-phenylacetamide hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(3-oxopyrrolidine-1-carbonyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(5-chloro-2-methoxybenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]methanesulfonamide,    7-acetyl-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-propionyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    9-hydroxy-2-(3-phenylallyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-methyl-2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N,N-dimethyl-2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-(2-methanesulfonylethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-[2-(2-oxopyrrolidin-1-yl)ethyl]-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-N-methylmethanesulfonamide,    2-(3-chloro-5-methoxybenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-(pyridin-4-ylmethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-(4-fluorobenzyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chlorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-hydroxymethyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-fluorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(thiazol-5-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido [1,2-a]pyrazine-7-carboxylic acid methylamide,    N,N-dimethyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chloro-4-fluorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-4-hydroxymethyl-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxylic acid methylamide hydrochloride,    2-(3-chlorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-chloro-2-hydroxybenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(9-hydroxy-1,8-dioxo-1,8-dihydro-pyrido[1,2-a]pyrazin-2-yl)-N-methyl-N-phenylacetamide hydrochloride,    N-methyl-2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N,N-dimethyl-2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    3-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2,2-dimethyl-3-oxopropyl acetate hydrochloride    2-(3-chlorobenzyl)-9-hydroxy-7-(3-hydroxy-2,2-dimethylpropionyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyrazin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(2-methyl-2H-1,2,4-triazol-3-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-(2-fluoroethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-benzyl-N-methyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chlorobenzyl)-9-hydroxy-7-phenylsulfanyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    7-benzenesulfinyl-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    7-benzenesulfonyl-2-(3-chlorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]isobutyramide,    N-[2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetamide,    2-(3-chloro-4-fluorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-4-hydroxymethyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]propionamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-phenylacetamide,    7-acetyl-2-(3-chloro-4-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-methylsulfanyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-methanesulfonyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-methanesulfinyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-(5-methylthiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    7-(2,2-dimethylpropionyl)-2-(4-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-methyl-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-[3-(2-chloro-6-fluarophenyl)propyl]-7-(2,2-dimethylpropionyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(4-methylthiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]butyramide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]benzamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-3-phenylpropionamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-N-methylacetamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-methoxyacetamide,    methyl 2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxylate,    3-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-1,1-dimethylurea,    methyl[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]carbamate,    2-[3-(2-chloro-6-fluorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-oxopropionamide,    N-benzyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chlorobenzyl)-9-hydroxy-7-(1H-pyrazol-3-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-(naphthalen-1-ylmethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-benzhydryl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyrimidin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(2-methyl-2-phenylpropionyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-(4-tert-butylbenzyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]cyclapentanecarboxamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-(4-fluorophenyl)acetamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2,2-dimethylpropionamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-phenylisobutyramide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-4-fluorobenzamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]pyridine-2-carboxamide trifluoroacetate,    2-(3-chlorobenzyl)-9-hydroxy-7-isopropylamino-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-7-diethylamino-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-isobutylamino-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-isopropyl-3-methylbutyramide,    2-(3-chlorobenzyl)-7-ethylamino-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]nicotinamide trifluoroacetate,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]isonicotinamide trifluoroacetate,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]furan-2-carboxamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]thiophene-2-carboxamide,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyridazin-3-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3,4-difluorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chloro-2-fluorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-chlorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-chloro-3-fluorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-chloro-2-methoxybenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-1-methyl-1H-pyrrole-2-carboxamide,    2-[3-(4-chlorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-[3-(2-chlorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-[3-(3-chlorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(3-methyl-1,2,4-thiadiazol-5-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    5-fluoro-2-[9-hydroxy-1,8-dioxo-7-(thiazol-2-yl)-1,3,4,8-tetrahydro-pyrido[1,2-a]pyrazin-2-ylmethyl]-N-methylbenzamide,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-N-isobutylacetamide,    N-[2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetamide,    N-[2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]benzamide,    N-[2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]methanesulfonamide,    2-(4-fluorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione trifluoroacetate,    2-(2-fluorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-fluorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-fluorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(2-chlorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    9-hydroxy-2-(naphthalen-2-ylmethyl)-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-[3-(3-chloro-2-fluorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-[3-(4-chloro-3-fluorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-[3-(4-fluorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-[3-(3-fluorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    9-hydroxy-2-(3-phenylpropyl)-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-2-fluorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-methoxyacetamide,    N-[2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1 2-a]pyrazin-7-yl]-2-propanesulfonamide,    N-[2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]nicotinamide trifluoroacetate,    N-[2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]isobutyramide,    N-(2-methoxyethyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-ethyl-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-{2-[3-(2-chloro-6-fluorophenyl)propyl]-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl}acetamide,    N-[2-(3-chloro-2-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetamide hydrochloride,    methyl 5-fluoro-2-[9-hydroxy-1,8-dioxo-7-(thiazol-2-yl)-1,3,4,8-tetrahydro-pyrido[1,2-a]pyrazin-2-ylmethyl]benzoate,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-2-fluorobenzyl)-9-hydroxy-7-(pyridin-3-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-[3-(2-chloro-6-fluorophenyl)propyl]-9-hydroxy-7-(pyridin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(benzofuran-2-ylmethyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-(1,2-diphenylethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-[2-(3-chloro-2-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetamide,    2-[3-(2-fluorophenyl)propyl]-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-(1,3-diphenylpropyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    5-fluoro-2-{3-[9-hydroxy-1,8-dioxo-7-(thiazol-2-yl)-1,3,4,8-tetrahydro-pyrido[1,2-a]pyrazin-2-yl]propyl}-N-methylbenzamide,    2-[3-(2-chloro-6-fluorophenyl)propyl]-7-(2,2-dimethylpropionyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-isobutyryl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    9-hydroxy-2-(4-phenylbutyl)-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    9-hydroxy-2-pentyl-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-2-fluorobenzyl)-9-hydroxy-7-(pyridin-4-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-7-(pyridin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-2-fluorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione trifluoroacetate,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-7-(2-methyl-2H-1,2,4-triazol-3-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    7-acetyl-2-(4-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-fluorobenzyl)-9-hydroxy-7-isobutyryl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]isonicotinamide hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-7-(pyrazin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    N-[2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]isobutyramide,    2-(4-chloro-2-hydroxybenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    9-hydroxy-2-(3-phenylbutyl)-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chloro-2-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]nicotinamide hydrochloride,    N-[2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]methanesulfonamide,    2-(3-chloro-4-propoxybenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-isopropoxybenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-benzyloxy-3-chlorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-chloro-2-propoxybenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-chloro-2-isopropoxybenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(2-benzyloxy-4-chlorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-7-(2-methyl-2H-1,2,4-triazol-3-yl)-2H-pyrido[1,2-a]-pyrazine-1,8-dione hydrochloride,    N-methyl-2-(3-chloro-2-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3-chlorobenzyl)-7-(2,2-dimethylbutyryl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-fluorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-2-fluorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-fluorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-{5-fluoro-2-[9-hydroxy-1,8-dioxo-7-(thiazol-2-yl)-1,3,4,8-tetrahydro-pyrido[1,2-a]pyrazin-2-ylmethyl]phenyl}acetamide hydrochloride,    2-(3-chloro-2-fluorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-3,4-dihydro-2}1-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    5-fluoro-2-[9-hydroxy-1,8-dioxo-7-(thiazol-2-yl)-1,3,4,8-tetrahydro-pyrido[1,2-a]pyrazin-2-ylmethyl]benzoic acid hydrochloride,    2-(3,4-difluorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-benzyl-N-methyl-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    N-(pyridin-3-ylmethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    N-(pyridin-2-ylmethyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    2-(3,4-dichlorobenzyl)-9-hydroxy-7-(pyridin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione trifluoroacetate,    N-(2-oxopropyl)-2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    2-(3-fluorobenzyl)-9-hydroxy-7-(pyridin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    7-(2,2-dimethylpropionyl)-2-(3-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-(2-fluorobenzyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-(4-fluorobenzyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-methyl-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-benzyl-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    N-methyl-2-(4-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    7-(2,2-dimethylbutyryl)-2-(4-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3,4-dichlorobenzyl)-9-hydroxy-7-(pyrazin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3,4-dichlorobenzyl)-9-hydroxy-7-isobutyryl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-fluorobenzyl)-9-hydroxy-7-isobutyryl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    7-(2,2-dimethylpropionyl)-2-(4-fluorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazme-1,8-dione,    2-(4-fluorobenzyl)-9-hydroxy-7-(3-methylbutyryl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-methyl-2-(3,4-difluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(4-fluorobenzyl)-9-hydroxy-7-(3-methoxy-2,2-dimethylpropionyl)-3,4-dihydro-2H-pyrido [1,2-a]pyrazine-1,8-dione,    9-benzyloxy-7-bromo-2-(3-chlorobenzyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-chlorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-5-propoxybenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-5-isopropoxybenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-benzyloxy-5-chlorobenzyl)-9-hydroxy-7-(thiazol-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-chlorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-(pyridin-3-yl) acetamide hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-(pyridin-4-yl)acetamide hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-(pyridin-2-yl) acetamide hydrochloride,    2-(3-fluorobenzyl)-9-hydroxy-7-(pyrimidin-4-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-fluorobenzyl)-9-hydroxy-7-(pyrazin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chloro-4-fluorobenzyl)-9-hydroxy-7-(2-methyl-2H-1,2,4-triazol-3-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]-3,3-dimethylbutyramide,2-(3-fluorobenzyl)-9-hydroxy-4-methyl-7-(pyridin-2-yl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    7-(2,2-dimethylpropionyl)-2-(4-fluorobenzyl)-9-hydroxy-4-methyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    7-(2,2-dimethylpropionyl)-2-(4-fluorobenzyl)-9-hydroxy-6-methoxymethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-(pyridin-2-ylmethyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    N-(furan-2-ylmethyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    7-(2,2-dimethylpropionyl)-2-(4-fluorobenzyl)-9-hydroxy-4,4-dimethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    7-bromo-2-(4-fluorobenzyl)-9-hydroxy-4,4-dimethyl-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-4,4-dimethyl-7-(pyridin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-(4-dimethylaminobenzyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-7-(pyrazin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-7-(pyrazin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]benzenesulfonamide,    N-[2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]benzylsulfonamide,    N-[2-(3-chloro-4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazin-7-yl]-2-thiophenesulfonamide,    N-(4-methanesulfonylbenzyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-6-(2-hydroxy-3,3-dimethylbutyl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-[2-(3-chlorobenzyl)-9-hydroxy-4-methyl-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetamide,    2-(4-fluorobenzyl)-9-hydroxy-6-methoxymethyl-7-(pyridin-2-yl)-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(4-fluorobenzyl)-9-hydroxy-7-(3-methoxy-2,2-dimethylpropionyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-(4-methoxypyrimidin-2-ylmethyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide hydrochloride,    6-(3,3-dimethyl-2-oxobutyl)-7-(2,2-dimethylpropionyl)-2-(4-fluorobenzyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    N-(4-acetylaminobenzyl)-2-(4-fluorobenzyl)-9-hydroxy-1,8-dioxo-1,3,4,8-tetrahydro-2H-pyrido[1,2-a]pyrazine-7-carboxamide,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-(2-hydroxyethyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-(1-hydroxypropyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-(3-hydroxypropyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-(1-hydroxy-2-methylpropyl)-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-phenethyl-2H-pyrido[1,2-a]pyrazine-1,8-dione,    2-(4-fluorobenzyl)-9-hydroxy-2H-pyrazino[1,2-c]pyrimidine-1,8-dione hydrochloride,    2-(3,4-dichlorobenzyl)-9-hydroxy-4-isopropyl-2H-pyrido[1,2-a]pyrazine-1,8-dione hydrochloride,    2-(3-chlorobenzyl)-9-hydroxy-4-methyl-2H-pyrido[1,2-d][1,2,4]triazine-1,8-dione,    2-(3-chlorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione,    7-(2,2-dimethylpropionyl)-2-(4-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione,    7-(2,2-dimethylpropionyl)-2-(4-fluorobenzyl)-9-hydroxy-2H-pyrido[1,2-a]pyrazine-1,8-dione sodium salt,    N-[2-(3-chlorobenzyl)-9-hydroxy-1,8-dioxo-1,8-dihydro-2H-pyrido[1,2-a]pyrazin-7-yl]acetamide sodium salt, and    2-(3-chlorobenzyl)-7-(2,2-dimethylpropionyl)-9-hydroxy-3,4-dihydro-2H-pyrido[1,2-a]pyrazine-1,8-dione sodium salt,    or a pharmaceutically acceptable salt thereof.    
     
     
         26 . A pharmaceutical composition comprising a nitrogen-containing fused ring compound of  claim 1 , or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.  
     
     
         27 . An anti-HIV agent comprising a nitrogen-containing fused ring compound of  claim 1  or a pharmaceutically acceptable salt thereof as an active ingredient.  
     
     
         28 . An integrase inhibitor comprising a nitrogen-containing fused ring compound of  claim 1  or a pharmaceutically acceptable salt thereof as an active ingredient.  
     
     
         29 . An antivirus agent comprising a nitrogen-containing fused ring compound of  claim 1 , or a pharmaceutically acceptable salt thereof as an active ingredient.  
     
     
         30 . An anti-HIV composition comprising a nitrogen-containing fused ring compound of  claim 1 , or a pharmaceutically acceptable salt thereof and one or more other kinds of anti-HIV active substances as active ingredients.  
     
     
         31 . An anti-HIV agent comprising a nitrogen-containing fused ring compound of  claim 1 , or a pharmaceutically acceptable salt thereof as an active ingredient, which is used for a multiple drug therapy with other anti-HIV agents.  
     
     
         32 . Use of a nitrogen-containing fused ring compound of  claim 1 , or a pharmaceutically acceptable salt thereof for the production of an anti-HIV agent.  
     
     
         33 . Use of a nitrogen-containing fused ring compound of  claim 1 , or a pharmaceutically acceptable salt thereof for the production of an integrase inhibitor.  
     
     
         34 . Use of a nitrogen-containing fused ring compound of  claim 1 , or a pharmaceutically acceptable salt thereof for the production of an antivirus agent.  
     
     
         35 . A method for the prophylaxis or treatment of an HIV infectious disease, which comprises administering an effective amount of a nitrogen-containing fused ring compound of  claim 1  or a pharmaceutically acceptable salt thereof to a mammal.  
     
     
         36 . The method of  claim 35 , further comprising administering an effective amount of at least one kind of other anti-HIV active substance to the mammal.  
     
     
         37 . A method of inhibiting integrase, which comprises administering an effective amount of a nitrogen-containing fused ring compound of  claim 1  or a pharmaceutically acceptable salt thereof to a mammal.  
     
     
         38 . A method for the prophylaxis or treatment of a viral infectious disease, which comprises administering an effective amount of a nitrogen-containing fused ring compound of  claim 1  or a pharmaceutically acceptable salt thereof to a mammal.