A compound of formula: or a pharmaceutically acceptable salt thereof, wherein the phenyl ring A is substituted in the meta or ortho position with the group and wherein R 1 is halogen, R 2 is a substituted (C 1 -C 6)alkyl, or a group -CHR 5 -(C=O)-R 6 where R 5 is H, or an optionally substituted (C 1 -C 6)alkyl, and R 6 is -OH, or NR 7 R 8, where R 7 and R 8 are independently H, an optionally substituted group selected from (C 1 -C 10)alkyl, hetero(C 1 -C 10)alkyl, (C 3 -C 9)cycloalkyl, hetero(C 3 -C 9)cycloalkyl, aryl, and heteroaryl, or if taken together with the N atom to which they are attached, R 7 and R 8 form an optionally substituted N-heterocycle or an optionally substituted heteroaryl with the N atom to which they are each attached, X 1 is O or NR 9, where R 9 is H or an optionally substituted alkyl, X 2 is O or N, R 3 and R 4 are independently H, an optionally substituted group selected from (C 1 -C 10)alkyl, hetero(C 1 -C 10)alkyl, (C 3 -C 9)cycloalkyl, hetero(C 3 -C 9)cycloalkyl, aryl and heteroaryl, or if taken together with the N atom to which they are attached when X 2 is N, R 3 and R 4 form an optionally substituted N-heterocycle or an optionally substituted heteroaryl with the N atom to which they are each attached, with the proviso that - when X 1 is O, X 2 is not O, - when X 1 is NR 9, X 2 is not N, - when X 2 is O, one of the groups R 3 or R 4 is absent, - when X 1 is NR 9, and X 2 is O, R 3 or R 4 is an optionally substituted group selected from (C 1 -C 10)alkyl, hetero(C 1 -C 10)alkyl, (C 3 -C 9)cycloalkyl, hetero (C 3 -C 9)cycloalkyl, aryl, or heteroaryl, wherein R 9 is H or an optionally substituted alkyl, wherein substituted (C 1 -C 6) alkyl is a (C 1 -C 6) alkyl group substituted with OH, COOH, CN, SH, F, NH 2, NHR' or NR'R", wherein R', R" are hydrogen or C 1 -C 6 alkyl. R 1 is halogen, R 2 is a substituted (C 1 -C 6)alkyl, or a group -CHR 5 -(C=O)-R 6 where R 5 is H, or an optionally substituted (C 1 -C 6)alkyl, and R 6 is -OH, or NR 7 R 8, where R 7 and R 8 are independently H, an optionally substituted group selected from (C 1 -C 10)alkyl, hetero(C 1 -C 10)alkyl, (C 3 -C 9)cycloalkyl, hetero(C 3 -C 9)cycloalkyl, aryl, and heteroaryl, or if taken together with the N atom to which they are attached, R 7 and R 8 form an optionally substituted N-heterocycle or an optionally substituted heteroaryl with the N atom to which they are each attached, X 1 is O or NR 9, where R 9 is H or an optionally substituted alkyl, X 2 is O or N, R 3 and R 4 are independently H, an optionally substituted group selected from (C 1 -C 10)alkyl, hetero(C 1 -C 10)alkyl, (C 3 -C 9)cycloalkyl, hetero(C 3 -C 9)cycloalkyl, aryl and heteroaryl, or if taken together with the N atom to which they are attached when X 2 is N, R 3 and R 4 form an optionally substituted N-heterocycle or an optionally substituted heteroaryl with the N atom to which they are each attached, with the proviso that - when X 1 is O, X 2 is not O, - when X 1 is NR 9, X 2 is not N, - when X 2 is O, one of the groups R 3 or R 4 is absent, - when X 1 is NR 9, and X 2 is O, R 3 or R 4 is an optionally substituted group selected from (C 1 -C 10)alkyl, hetero(C 1 -C 10)alkyl, (C 3 -C 9)cycloalkyl, hetero (C 3 -C 9)cycloalkyl, aryl, or heteroaryl, wherein R 9 is H or an optionally substituted alkyl, wherein substituted (C 1 -C 6) alkyl is a (C 1 -C 6) alkyl group substituted with OH, COOH, CN, SH, F, NH 2, NHR' or NR'R", wherein R', R" are hydrogen or C 1 -C 6 alkyl. - when X 1 is O, X 2 is not O, - when X 1 is NR 9, X 2 is not N, - when X 2 is O, one of the groups R 3 or R 4 is absent, - when X 1 is NR 9, and X 2 is O, R 3 or R 4 is an optionally substituted group selected from (C 1 -C 10)alkyl, hetero(C 1 -C 10)alkyl, (C 3 -C 9)cycloalkyl, hetero (C 3 -C 9)cycloalkyl, aryl, or heteroaryl,