Hydroxamic acid derivatives as inhibitors of HDAC enzymatic activity

1. A compound of formula (I) or a salt or N-oxide thereof:

wherein

Y 1 is a bond, —(C═O)—, —S(O 2 )—, —C(═O)—, —OC(═O)—, (C═O)NR 3 —, —NR 3 (C═O)—, —S(O 2 )NR 3 —, —NR 3 S(O 2 )—, or —NR 3 (C═O)NR 5 —, wherein R 3 and R 5 are independently hydrogen or optionally substituted (C 1 -C 6 )alkyl,

L 1 is a divalent radical of formula -(Alk 1 ) m (Q) n (Alk 2 ) P -wherein

m, n and p are independently 0 or 1,

Q is (i) an optionally substituted divalent mono- or bicyclic carbocyclic or heterocyclic radical having 5 - 13 ring members, or (ii), in the case where p is 0, a divalent radical of formula -Q 1 -X 2 —wherein X 2 is —O—, —S—or NR A —wherein R A is hydrogen or optionally substituted C 1 -C 3 alkyl, and Q 1 is an optionally substituted divalent mono- or bicyclic carbocyclic or heterocyclic radical having 5 -13 ring members,

Alk 1 and Alk 2 independently represent optionally substituted divalent C 3 -C 7 cycloalkyl radicals, or optionally substituted straight or branched, C 1 -C 6 alkylene, C 2 -C 6 alkenylene, or C 2 -C 6 alkynylene radicals which may optionally contain or terminate in an ether (—O—), thioether (—S—) or amino

(—NR A —) link wherein R A is hydrogen or optionally substituted C 1 -C 3 alkyl;

z is 0 or 1;

A represents an optionally substituted mono-, bi- or tri-cyclic carbocyclic or heterocyclic ring system; and

-[Linker]- represents a divalent linker radical linking a ring atom in A with the hydroxamic acid group —CONHOH and selected from linkers represented by formulas identified in a, b, c, or d:

a. —(CH 2 ) x —Z-L 2 -wherein x is 0, Z is —C(═O)—, —NHC(═O)—or —C(═O)NH—, and L 2 is —(CH 2 ) 5 —, —(CH 2 ) 6 —, or —(CH 2 ) 7 ;

b. —(CH 2 ) x -L 3 -Ar 1 -L 4 -wherein x is 0, L 3 is —NHS(═O) 2 —, —S(═O) 2 NH—, —S(═O) 2 —or a straight chain C 3 -C 5 alkylene radical which may optionally contain an ether (—O—), thioether (—S—) or amino (—NR A —) link wherein R A is hydrogen or optionally substituted C 1 -C 3 alkyl, L 4 is —CH═CH— or —CH 2 —, and Ar 1 is divalent radical selected from the following:

wherein X is 0, S or NH;

c. —(CH 2 ) x -L 3 -Ar 1 -L 4 -, wherein x is 0, L 3 and L 4 are bonds, and Ar 1 is a divalent phenyl radical or a divalent bicyclic heteroaryl radical having 9 to13 ring members;

d. —(CH 2 ) x -L 3 -B—Ar l -L 4 - wherein x is 0, Ar 1 is divalent radical selected from the following:

L 3 is a bond, —NHS(═O) 2 —, —S(═O) 2 NH—, —S(═O) 2 —or a straight chain C 3 -C 5 alkylene radical which may optionally contain an ether (—O—), thioether (—S—) or amino (—NR A —) link wherein R A is hydrogen or optionally substituted C l -C 3 alkyl, and L 4 is a bond, —CH═CH—or —CH 2 —; and B is a mono- or bi-cyclic heterocyclic ring system; and

R is a radical of formula (X) or (Y):

wherein

R 1 is a carboxylic acid group (—COOH), or an ester group which is hydrolysable by one or more intracellular carboxylesterase enzymes to a carboxylic acid group;

R 4 is hydrogen; or optionally substituted C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, aryl, aryl(C 1 -C 6 alkyl)-, heteroaryl, heteroaryl(C 1 -C 6 alkyl)-, —(C═O)R 3 , —(C═O)OR 3 , or —(C═O)NR 3 wherein R 3 is hydrogen or optionally substituted (C 1 -C 6 )alkyl, C 3 -C 7 cycloalkyl, aryl, aryl(C 1 -C 6 alkyl)-, heteroaryl, or heteroaryl(C 1 -C 6 alkyl)-;

R 4 1 is hydrogen or optionally substituted C l -C 6 alkyl; and

B is a monocyclic heterocyclic ring of 5 or 6 ring atoms wherein R 1 is linked to a ring carbon adjacent the ring nitrogen shown, and ring B is optionally fused to a second carbocyclic or heterocyclic ring of 5 or 6 ring atoms in which case the bond shown intersected by a wavy line may be from a ring atom in said second ring.

2. A compound as claimed in claim 1 wherein -[Linker]-represents a divalent radical of formula —(CH 2 ) x —Z-L 2 - wherein x is 0, Z is —C(═O)—, —NHC(═O)—or —C(═O)NH—, and L 2 is —(CH 2 ) 5 —, —(CH 2 ) 6 - —, or —(CH 2 ) 7 —.

3. A compound as claimed in claim 1 wherein-[Linker]-represents a divalent radical of formula —(CH 2 ) x -L 3 -Ar 1 -L 4 - wherein x is 0, L 3 is —NHS(═O) 2 —, —S(═O) 2 NH—, —S(═O) 2 — or a straight chain C 3 -C 5 alkylene radical which may optionally contain an ether (—O—), thioether (—S—) or amino (—NR A —) link wherein R A is hydrogen or optionally substituted C l -C 3 alkyl, L 4 is —CH═CH— or —CH 2 —, and Ar 1 is divalent radical selected from the following:

wherein X is 0, S or NH.

4. A compound as claimed in claim 1 wherein -[Linker]-represents a divalent radical of formula —(CH 2 ) x -L 3 -Ar 1 -L 4 -, wherein x is 0, L 3 and L 4 are bonds, and Ar 1 is a divalent phenyl radical or a divalent bicyclic heteroaryl radical having 9 to 13 ring members.

5. A compound as claimed in claim 1 wherein -[Linker]-represents a divalent radical of formula —(CH 2 ) x -L 3 -B—Ar l -L 4 - wherein x is 0, Ar 1 is divalent radical selected from the following:

L 3 is a bond, —NHS(═O) 2 —, —S(═O) 2 NH—, —S(═O) 2 —or a straight chain C 3 -C 5 alkylene radical which may optionally contain an ether (—O—), thioether (—S—) or amino (—NR A —) link wherein R A is hydrogen or optionally substituted C l -C 3 alkyl, and L 4 is a bond, —CH═CH—or—CH 2 -; X is O, S, or NH and B is a mono- or bi-cyclic heterocyclic ring system.

6. A compound as claimed in claim 5 wherein B is selected from the following:

wherein X is N and W is NH, 0 or S.

7. A compound as claimed in claim 1 wherein A is one of the following ring systems, optionally substituted:

wherein R 10 is hydrogen or optionally substituted C 1 -C 6 alkyl, the bond intersected by the wavy lines shown as connected to a fixed atom connects to the Linker radical in the compounds (I), and the other bond shown as floating links any convenient ring atom of the ring system shown to the grouping RL 1 Y 1 [CH 2 ] z .

8. A compound as claimed in claim 1 wherein z is 0.

9. A compound as claimed in any claim 1 wherein Y 1 is a bond, —NR 3 —, —S—, —O—, —C(═O)NR 3 —, —NR 3 C(═O)—, or —C(═O)O—, wherein R 3 is hydrogen or optionally substituted C 1 -C 6 alkyl.

10. A compound as claimed in claim 1 wherein, in the radical L 1 , Alk 1 and Alk 2 , when present, are selected from —CH 2 —, —CH 2 CH 2 —, —CH 2 CH 2 CH 2 —, and divalent cyclopropyl, cyclopentyl and cyclohexyl radicals, and Q when present is a divalent phenylene radical or a mono-, or bi-cyclic heteroaryl radical having 5 to 13 ring members.

11. A compound as claimed in claim 1 wherein the radical -L 1 -Y 1 —[CH 2 ] z — is selected from —(CH 2 ) 3 NH—, —CH 2 C(═O)NH—, —CH 2 CH 2 C(═O)NH—, —CH 2 C(O)O—, —CH 2 S—, —CH 2 CH 2 C(O)O—, —(CH 2 ) 4 NH—, —CH 2 CH 2 S—, —CH 2 O, —CH 2 CH 2 O—,

12. A compound as claimed in claim 1 wherein the radical -L 1 -Y 1 —[CH 2 ] z — is —CH 2 —.

13. A compound as claimed in claim 1 wherein R 1 is an ester group of formula —(C═O)OR 9 wherein R 9 is

(i) R 7 R 8 CH— wherein R 7 is optionally substituted (C 1 -C 3 )alkyl-(Z 1 ) a —(C 1 -C 3 )alkyl- or (C 2 -C 3 )alkenyl-(Z 1 ) a —(C 1 -C 3 )alkyl- wherein a is 0 or 1 and Z 1 is —O—, —S—, or —NH—, and R 8 is hydrogen or (C 1 -C 3 )alkyl- or R 7 and R 8 taken together with the carbon to which they are attached form an optionally substituted C 3 -C 7 cycloalkyl ring or an optionally substituted heterocyclic ring of 5- or 6-ring atoms; or

(ii) optionally substituted phenyl or monocyclic heterocyclic having 5 or 6 ring atoms.

14. A compound as claimed in claim 13 wherein R 9 is methyl, ethyl, n- or iso-propyl, n- or sec-butyl, cyclohexyl, allyl, phenyl, benzyl, 2-, 3- or 4-pyridylmethyl, N-methylpiperidin-4-yl, tetrahydrofuran-3-yl or methoxyethyl.

15. A compound as claimed in claim 13 wherein R 9 is cyclopentyl.

16. A compound as claimed in claim 1 wherein R is a group of formula (X) wherein R 4 1 is hydrogen, and R 4 is hydrogen, methyl, ethyl, n-or isopropyl, cyclopropyl, cyclopentyl, cyclohexyl, phenyl, or pyridyl.

17. A compound as claimed in claim 1 wherein R is a group of formula (X) wherein R 4 l and R 4 are each hydrogen.

18. A compound as claimed in claim 1 wherein R is a group of formula (Y) wherein ring or ring system B selected from the following:

19. A compound as claimed in claim 1 having the structure of any of the compounds of the specific Examples herein.

20. A pharmaceutical composition comprising a compound as claimed in claim 1 , together with a pharmaceutically acceptable carrier.

21. A pharmaceutical composition as claimed in claim 20 which is adapted for topical administration and wherein, in the compound, R is attached to a methylene (—CH 2 )— radical.