Nanoluc suicide substrates

1. A compound of formula (I)

or a tautomer or a salt thereof, wherein:

R 1 is optionally substituted aryl, optionally substituted heteroaryl, optionally substituted heterocycle, or optionally substituted cycloalkyl, wherein R 1 is substituted with at least one group that is -Q-L-Z;

Q is —O—, —NR Q —, —NR Q —CO—, —CO—NR Q —, —O—CO—NR Q —, or —NR Q —CO—O—;

L is —(CR 1a R 1b ) m —, —(CR 1x R 1y —CR 1x R 1y —O) t1 —(CR 1x R 1y ) t2 —Q 1 —, —(CR 1x R 1y ) t2 -A-(CR 1x R 1y —CR 1x R 1y —O) t1 -Q 1 -, wherein each Q 1 is independently a bond, —O—, or —NR Q —, and A is a bond, —O—, —NR Q —, —NR Q —CO—, —CO—NR Q —, —O—CO—NR Q —, or —NR Q —CO—O—;

Z is —COOR 2 , —SO 2 —OR 3 , —PO(OR 4 )(OR 5 ), halo, azide, C 2 -C 10 alkynyl, a biotin moiety, —NR 6 R 7 , or —NR 8 —CO—R 9 ;

R 2 , R 3 , R 4 , R 5 , R 8 , R 9 , R 10 , R 11 , and R 12 at each occurrence are independently hydrogen, optionally substituted C 1 -C 8 alkyl, optionally substituted aryl, optionally substituted cycloalkyl, optionally substituted heteroaryl, optionally substituted heterocycle, optionally substituted heteroalkyl, or an energy acceptor;

R 6 and R 7 at each occurrence are independently hydrogen, optionally substituted C 1 -C 8 alkyl, optionally substituted aryl, optionally substituted cycloalkyl, optionally substituted heteroaryl, optionally substituted heterocycle, optionally substituted heteroalkyl, or an energy acceptor; or R 6 and R 7 , together with the nitrogen atom to which they are attached, together form an optionally substituted ring;

R 1a , R 1b , R Q , R Q1 , R 1x , and R 1y at each occurrence are independently hydrogen, C 1 -C 4 alkyl, or C 1 -C 4 haloalkyl;

q is 0, 1, or 2;

m at each occurrence is independently 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12;

t1 at each occurrence is independently 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10; and

t2 is an integer from 0-5;

wherein, when a group is optionally substituted, it is either unsubstituted or substituted with one or more substituents independently selected from halogen, ═O, ═S, cyano, nitro, alkyl, alkenyl, alkynyl, haloalkyl, haloalkoxy, heteroalkyl, cycloalkyl, cycloalkenyl, aryl, heteroaryl, heterocycle, cycloalkylalkyl, heteroarylalkyl, arylalkyl, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, aryloxy, benzyloxy, amino, alkylamino, acylamino, aminoalkyl, arylamino, sulfonylamino, sulfinylamino, sulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl, sulfinyl, —COOH, amide, carbamate, and acyl; and

wherein the compound is not 4-[4-[[8-benzyl-6-(4-hydroxyphenyl)-3-oxo-7H-imidazo[1,2-a]pyrazin-2-yl]methyl]phenoxy]butanoic acid.

2. The compound of claim 1 , or a tautomer or a salt thereof, wherein q is 1.

3. The compound of claim 1 , or a tautomer or a salt thereof, wherein

R 1 is phenyl substituted with one substituent -Q-L-Z, and optionally further substituted with 1 or 2 substituents independently selected from halogen, cyano, nitro, haloalkyl, haloalkoxy, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, amino, alkylamino, dialkylamino, acylamino, aminoalkyl, sulfonylamino, sulfinylamino, sulfonyl, alkylsulfonyl, arylsulfonyl, aminosulfonyl, sulfinyl, —COOH, ketone, amide, carbamate, silyl, substituted silyl, t-butyldimethylsilyl, alkylsulfanyl, sulfanyl, and acyl;

Q is —O—, —NR Q —, —NR Q —CO—, —CO—NR Q —, —O—CO—NR Q —, or —NR Q —CO—O—;

L is —(CR 1a R 1b ) m —;

Z is —SO 2 —OR 3 , azide, —NR 6 R 7 , or —NR 8 —CO—R 9 ;

R 3 , R 6 , R 7 and R 8 are independently hydrogen, optionally substituted C 1 -C 8 alkyl, optionally substituted aryl, optionally substituted cycloalkyl, optionally substituted heteroaryl, or optionally substituted heterocycle; and

R 9 is optionally substituted heteroalkyl or an energy acceptor.

4. The compound of claim 3 , or a tautomer or a salt thereof, wherein

R 1 is phenyl substituted with one substituent -Q-L-Z, and is optionally further substituted with one halogen.

5. The compound of claim 1 , or a tautomer or a salt thereof, wherein the compound is a compound of formula (Ia)

or a tautomer or a salt thereof,

wherein

R 1z is halogen.

6. The compound of claim 5 , or a tautomer or a salt thereof, wherein

Q is O;

L is —(CR 1a R 1b ) m —;

R 1a and R 1b are hydrogen;

m is 5, 6, 7, 8, 9 or 10;

Z is —NR 8 —CO—R 9 ;

R 8 is hydrogen; and

R 9 is an energy acceptor.

7. The compound of claim 1 , or a tautomer or a salt thereof, wherein the energy acceptor is a fluorescent dye selected from a fluorescein, a rhodamine, a coumarin, a pyrene, a cyanine, a squaraine, and a boron-dipyrromethene.

8. The compound of claim 1 , or a tautomer or a salt thereof, wherein the group -Q-L-Z has a structure selected from:

9. The compound of claim 1 , selected from the group consisting of:

2-(4-((6-aminohexyl)oxy)-3-fluorobenzyl)-8-benzyl-6-(4-hydroxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one;

N-(6-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)hexyl)-3′,6′-bis(dimethylamino)-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-6-carboxamide;

6-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)hexane-1-sulfonic acid;

N-(6-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)hexyl)-3′,6′-dihydroxy-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-6-carboxamide;

N-(6-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)hexyl)-3-(5,5-difluoro-7-(1H-pyrrol-2-yl)-5H-514,614-dipyrrolo[1,2-c:2′,1′-f][1,3,2]diazaborinin-3-yl)propanamide;

N,N′-(6-((6-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)hexyl)carbamoyl)-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-3′,6′-diyl)bis(2,2,2-trifluoroacetamide);

N-(8-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)octyl)-3′,6′-dihydroxy-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-6-carboxamide;

N-(8-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)octyl)-3′,6′-bis(dimethylamino)-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-6-carboxamide;

3-(2-(2-aminoethoxy)ethoxy)-N-(8-(4-((1-benzyl-3-(4-hydroxyphenyl)-6-oxo-2,6-dihydropyrrolo[1,2-a]pyrazin-7-yl)methyl)-2-fluorophenoxy)octyl)propanamide;

N-(2-(2-(3-((8-(4-((1-benzyl-3-(4-hydroxyphenyl)-6-oxo-2,6-dihydropyrrolo[1,2-a]pyrazin-7-yl)methyl)-2-fluorophenoxy)octyl)amino)-3-oxopropoxy)ethoxy)ethyl)-3′,6′-dihydroxy-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-6-carboxamide;

N-(2-(2-(3-((8-(4-((1-benzyl-3-(4-hydroxyphenyl)-6-oxo-2,6-dihydropyrrolo[1,2-a]pyrazin-7-yl)methyl)-2-fluorophenoxy)octyl)amino)-3-oxopropoxy)ethoxy)ethyl)-3′,6′-bis(dimethylamino)-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-6-carboxamide;

6-((8-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)octyl)carbamoyl)-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-3′,6′-diyl diacetate;

2-(4-((6-azidohexyl)oxy)-3-fluorobenzyl)-8-benzyl-6-(4-hydroxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one;

5-((8-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)octyl)carbamoyl)-2-(2,7-difluoro-3,6-dihydroxyxanthylium-9-yl)benzoate;

5-((8-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)octyl)carbamoyl)-2-(3,11-dihydroxydibenzo[c,h]xanthen-14-ium-7-yl)benzoate; and

N1-(8-(4-((8-benzyl-6-(4-hydroxyphenyl)-3-oxo-3,7-dihydroimidazo[1,2-a]pyrazin-2-yl)methyl)-2-fluorophenoxy)octyl)-N4-(2-(5,5-difluoro-1,3-dimethyl-5H-5λ 4 ,6λ 4 -dipyrrolo[1,2-c:2′,1′-f][1,3,2]diazaborinin-10-yl)ethyl)succinamide,

or a tautomer or a salt thereof.