Prodrugs of azo compounds and their salts

A compound of formula I-A, pharmaceutically acceptable salts or solvates thereof:

• wherein;
• R1 and R3 are the same or different and independently selected from hydrogen,
• wherein R2 is selected from the group consisting of optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl;
• R4 is selected from the group consisting of optionally substituted alkyl, alkenyl, alkynyl, —(CH2—CH2—O)n—, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl, where n is from 1-20;
• R17 is selected from optionally substituted linear or branched alkylene group, wherein alkylene is optionally substituted with amino, alkylamino and dialkylamino group;
• R18 is selected from NH2, —NR20R21, wherein R20 and R21 are each independently selected from hydrogen, optionally substituted alkyl, —C(O)—R22, wherein R22 is selected from optionally substituted alkyl, cycloalkyl, heterocycloalkyl, heteroaryl, and aryl group;
• R5 is selected from hydrogen, —OH, —OR8, and
• wherein R9 is selected from the group consisting of optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, amino, alkyl-ester, alkoxy, heterocycloalkoxy, heteroaryloxy, cycloalkoxy, aryloxy, amino acid linked via ester or amide linkage at the point of attachment, —(CH2—CH2—O)n—, or NR10R11, where n is from 1-20;
• R10 and R11 are the same or different and independently selected from hydrogen or optionally substituted alkyl, cycloalkyl, aryl, heterocycloalkyl, and heteroaryl group;
• R8 is selected from the group consisting of optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl;
• R6 is a phenylene group, wherein the phenylene group is zero to four times substituted by R7, wherein R7 is selected from hydrogen, —OH, —OR12,
• and—R19;
• wherein R12 is selected from the group consisting of optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl;
• R13 is selected from group consisting of optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, alkyl-ester, amino, alkoxy, heterocycloalkoxy, heteroaryloxy, cycloalkoxy, aryloxy, aminoaryl, or amino acid linked via ester or amide linkage at the point of attachment, —(CH2—CH2—O)n—, or NR14R15, where n is from 1-20;
• R14 and R15 are each independently selected from hydrogen, optionally substituted alkyl, heterocycloalkyl, aryl group;
• R16 selected from optionally substituted alkylene(C1-6) group;
• R19 is selected from —O—R23—O—C(O)—R24, —O—C(O)—R23—R27, and —O—R23— R28, wherein R23 is optionally substituted linear or branched alkylene;
• R24 is selected from optionally substituted alkoxy, cycloalkoxy, heterocycloalkoxy, heteroaryloxy, aryloxy group and —N(R25R26), wherein R25, R26 are each independently selected from hydrogen, optionally substituted alkyl and aryl, wherein alkyl and aryl are optionally substituted with OH, SH, F, Cl, Br, I, and optionally substituted hydroxyalkyl, amino group, or R25 and R26 is taken together to form an optionally substituted heterocycloalkyl ring, wherein the heterocycloalkyl ring is optionally substituted with alkyl, hydroxyalkyl, —OH, —SH, F, Cl, Br, I, and optionally substituted amino group;
• R27 is selected from optionally substituted alkyl, cycloalkyl, heterocycloalkyl, heteroaryl, aryl and —N(R25R26) group;
• R28 is selected from optionally substituted alkyl, cycloalkyl, heterocycloalkyl, heteroaryl, and aryl group;
• wherein heterocycloalkyl, heteroaryl in R28 is optionally substituted with alkyl, hydroxyalkyl group, OH, SH, F, Cl, Br, I, and optionally substituted, amino and oxo group;
• R29 and R30 are each independently selected from hydrogen, and —R23—O—C(O)—O—R31;
• wherein R31 is selected from optionally substituted alkyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl group;
• with the proviso that all substitutions at R1, R3, R5, R7 are not hydrogen when R6 is phenylene;
• when anyone substitution at R1 or R3 is other than hydrogen and R6 is phenylene, then R5 and R7 is not hydrogen;
• when substitution at R1, R3, R7 is hydrogen then R5 is not —OH;
• when substitution at R1, R3, R5 is hydrogen and R6 is phenylene then single R7 substitution on phenylene is not —OH or —O-(alkyls-3) at either ortho or para position;
• when substitution at R1, R3 is hydrogen, R5 is —OH and R6 is phenylene then R7 substitution on phenylene is not —OH para position.