Substituted organofluoroborates as imaging agents

1. A positron emitting compound or salt thereof having a half-life with respect to solvolytic de- 18 F-fluoridation at physiological pH of about 1000 minutes or more, wherein the compound is of the formula (IV):

wherein:

B is boron;

each Y 1 is independently selected from the group consisting of R 1 , 18 F and 19 F;

n=1 or 2;

Y 2 is selected from the group consisting of R 2 , 18 F and 19 F;

R 1 is a non-interfering substituent with regard to fluoridation of B;

R 2 is a non-interfering substituent with regard to fluoridation of B;

at least one of (Y 1 ) n and Y 2 is 18 F;

Q 1 is —C≡CR 8 ,

or —R 10 C═CR 11 R 12 ;

R 8 is —N + R 25 R 26 R 27 , P + R 28 R 29 R 30 , —S + R 31 R 32 , —NR 33 R 34 ,

a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is substituted with at least one substituent that is a biomolecule and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the carbon atom of —C≡CR 8 through a carbon atom;

each of R 25 , R 26 and R 27 is independently a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the nitrogen atom of —N + R 25 R 26 R 27 through a carbon atom, or R 25 is absent and R 26 and R 27 are joined so that —N + R 25 R 26 R 27 forms a positively charged nitrogen containing heterocyclic group which is unsubstituted or substituted;

each of R 28 , R 29 , and R 30 is independently a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the phosphorus atom of —P + R 28 R 29 R 30 through a carbon atom;

each of R 31 and R 32 is independently H, D, a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the sulfur atom of —S + R 31 R 32 through a carbon atom;

each of R 33 and R 34 is independently H, D, a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the nitrogen atom of —NR 33 R 34 through a carbon atom;

R 35 is a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is substituted with at least one substituent that is a biomolecule and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the carbon atom of

through a carbon atom;

R 9 is —NR 38 R 39 ,

a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is substituted with at least one substituent that is a biomolecule and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the carbon atom of

through a carbon atom;

each of R 38 and R 39 is independently H, D, a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the nitrogen atom of —NR 38 R 39 through a carbon atom;

R 40 is a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is substituted with at least one substituent that is a biomolecule and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the carbon atom of

through a carbon atom;

each of R 10 , R 11 , and R 12 is independently H, D, F, Cl, Br, I, CX 3 , —N + R 41 R 42 R 43 , —P + R 44 R 45 R 46 , —S + R 47 R 48 , a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the carbon atom of —R 10 C═CR 11 R 12 through a carbon atom, and each X is the same or different and is F, Cl, Br, or I;

each of R 41 , R 42 and R 43 is independently H, D, a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the nitrogen atom of —N + R 41 R 42 R 43 through a carbon atom, or R 41 is absent and R 42 and R 43 are joined so that —N + R 41 R 42 R 43 forms a positively charged nitrogen containing heterocyclic group which is substituted or unsubstituted;

each of R 44 , R 45 , and R 46 is independently H, D, a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the phosphorus atom of —P + R 44 R 45 R 46 through a carbon atom; and

each of R 47 and R 48 is independently H, D, a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is unsubstituted or substituted and optionally includes at least one heteroatom interposed between two carbon atoms of the carbon chain of the group, wherein each of the at least one heteroatom is independently selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the sulfur atom of —S + R 47 R 48 through a carbon atom;

providing that Q 1 is selected such that the pK a of Ha of an acid of the formula:

is less than or equal to about 2.8.

2. The positron emitting compound or salt of claim 1 , wherein when Q 1 is substituted at the carbon alpha to the

group with a group that has a dissociable proton, the dissociable proton has a pKa greater than about 9 and contributes to a net positive charge on the group that has the dissociable proton.

3. The positron emitting compound or salt of claim 1 , wherein Q 1 is selected such that the pK a of H a of the acid of the formula

is less than or equal to about 2.4, less than or equal to about 2.0, less than or equal to about 1.5 or less than or equal to about 1.0.

4. The positron emitting compound or salt as defined in claim 1 , wherein

at least one of R 8 , R 9 , R 10 , R 11 , R 12 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 , R 33 , R 34 , R 35 , R 38 , R 39 , R 40 , R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 , and R 48 is a biomolecule, a linking group optionally joined to a biomolecule, or a group that is substituted with at least one substituent that is a biomolecule, or forms a group that is substituted with at least one substituent that is a biomolecule.

5. The positron emitting compound or salt of claim 1 , wherein Q 1 is —C≡CR 8 , or

and each R 8 and R 9 is as defined in claim 1 .

6. The positron emitting compound or salt of claim 1 , wherein:

Q 1 is —C≡CR 8 ;

wherein R 8 is a biomolecule, a linking group optionally joined to a biomolecule, a linear or branched C 1 -C 15 alkyl group, or a C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is substituted with at least one substituent that is a biomolecule and is optionally intercepted with at least one heteroatom selected from the group consisting of O, S, N and P, and each of the C 1 -C 15 alkyl group and the C 3 -C 18 cycloalkyl group is joined to the carbon atom of —C≡CR 8 through a carbon atom.

7. The positron emitting compound or salt of claim 1 , wherein each of R 1 and R 2 is independently a linear or branched C 1 -C 15 alkyl group or a non-aromatic C 3 -C 18 cycloalkyl group, wherein each of the C 1 -C 15 alkyl group and the non-aromatic C 3 -C 18 cycloalkyl group is unsubstituted or substituted and is optionally intercepted with at least one heteroatom selected from the group consisting of O, S, N and P.

8. The positron emitting compound or salt of claim 1 , wherein n is 2, each Y 1 is F and Y 2 is F.

9. The positron emitting compound or salt as defined in claim 1 , wherein at least two of (Y 1 ) n and Y 2 are 18 F.

10. The positron emitting compound or salt of claim 1 , conjugated to a biomolecule.

11. The positron emitting compound or salt of claim 10 , wherein the biomolecule is a peptide.

12. The positron emitting compound or salt of claim 1 , wherein Q 1 is —C≡CR 8 ; and R 8 is as defined in claim 1 .

13. The positron emitting compound or salt of claim 1 , wherein Q 1 is

and R 9 is as defined in claim 1 .

14. The positron emitting compound or salt of claim 1 , wherein Q 1 is —R 10 C═CR 11 R 12 ; and each of R 10 , R 11 , and R 12 is as defined in claim 1 .

15. The positron emitting compound or salt as defined in claim 1 , having a solvolytic de- 18 F-fluoridation half-life at physiological pH of about 5000 minutes or more.