Luciferin amides

1. A compound of formula (I):

wherein

n is 0;

is deleted;

each of X 1 and X 2 is S;

each of Y 1 and Y 2 is N;

Z is C(R c ) or C(R c R c′ ), in which each of R c and R c′ , independently, is H or C 1 -C 10 alkyl; provided that, when is a single bond, Z is C(R c R c′ ) and that, when is a double bond, Z is C(R c );

each of R 1 , R 4 , R 5 , and R 6 , independently, is H, halo, CN, OR e , SR e , NO 2 , N(R e R e′ ), C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 20 cycloalkyl, C 3 -C 20 cycloalkenyl, C 1 -C 20 heterocycloalkyl, C 1 -C 20 heterocycloalkenyl, aryl, heteroaryl, in which each of R e and R e′ , independently, is H or C 1 -C 10 alkyl;

R 2 and R 3 , together with the carbon atoms to which they are attached, are a 5 or 6-membered ring, each of which is optionally substituted with C 1 -C 10 alkyl or optionally fused with a 5 or 6-membered ring; and

each of R 7 and R 8 , independently, is H, C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 20 cycloalkyl, C 3 -C 20 cycloalkenyl, C 1 -C 20 heterocycloalkyl, C 1 -C 20 heterocycloalkenyl, aryl, or heteroaryl.

2. The compound of claim 1 , wherein R 2 and R 3 , together with the carbon atoms to which they are attached, are a 5-membered ring optionally substituted with CH 3 , or a 6-membered ring optionally substituted with CH 3 or optionally fused with a 5-membered ring.

3. The compound of claim 2 , wherein each of R 1 and R 4 , independently, is H, OH, or C 1 -C 10 alkyl.

4. The compound of claim 3 , wherein each of R 5 and R 6 is H and each of R 7 and R 8 , independently, is H or C 1 -C 10 alkyl.

5. The compound of claim 4 , wherein the compound is

6. The compound of claim 1 , wherein the compound is a D-isomer.

7. An imaging method, comprising:

contacting a cell comprising a luciferase and a fatty acid amide hydrolase with the compound of claim 1 ; and

detecting bioluminescent emission from the cell.

8. The method of claim 7 , wherein the luciferase is a wild-type luciferase.

9. The method of claim 8 , wherein the wild-type luciferase is a beetle luciferase.

10. The method of claim 9 , wherein the beetle luciferase is a firefly, click beetle, or railroad worm luciferase.

11. The method of claim 7 , wherein the luciferase is a mutated luciferase.

12. The method of claim 7 , wherein the contacting step is performed in a brain of a subject.

13. An imaging method, comprising:

contacting a cell comprising a fatty acid amide hydrolase with the compound of claim 1 ;

introducing a luciferase; and

detecting bioluminescent emission.

14. A compound of formula (I):

wherein

n is 0;

is deleted;

each of X 1 and X 2 is S;

each of Y 1 and Y 2 is N;

Z is C(R c ) or C(R c R c′ ), in which each of R c and R c′ , independently, is H or C 1 -C 10 alkyl; provided that, when is a single bond, Z is C(R c R c′ ) and that, when is a double bond, Z is C(R c );

each of R 1 , R 4 , R 5 , and R 6 , independently, is H, halo, CN, OR e , SR e , NO 2 , N(R e R e′ ), C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 20 cycloalkyl, C 3 -C 20 cycloalkenyl, C 1 -C 20 heterocycloalkyl, C 1 -C 20 heterocycloalkenyl, aryl, heteroaryl, in which each of R e and R e′ , independently, is H or C 1 -C 10 alkyl;

R 2 and R 3 , together with the carbon atoms to which they are attached, are a 5 or 6-membered ring, each of which is optionally substituted with C 1 -C 10 alkyl or optionally fused with a 5 or 6-membered ring;

R 7 is H, C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 20 cycloalkyl, C 3 -C 20 cycloalkenyl, C 1 -C 20 heterocycloalkyl, C 1 -C 20 heterocycloalkenyl, aryl, or heteroaryl; and

R 8 is C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 20 cycloalkyl, C 3 -C 20 cycloalkenyl, C 1 -C 20 heterocycloalkyl, C 1 -C 20 heterocycloalkenyl, aryl, or heteroaryl.

15. An imaging method, comprising:

contacting a cell comprising a luciferase and a fatty acid amide hydrolase with the compound of claim 14 ; and

detecting bioluminescent emission from the cell.

16. An imaging method, comprising:

contacting a cell comprising a fatty acid amide hydrolase with the compound of claim 14 ;

introducing a luciferase; and

detecting bioluminescent emission.