Tetracyclic indole derivatives as in vivo imaging agents and having peripheralbenzodiazepine receptor affinity (PBR)

A compound of Formula II:

• or a salt thereof wherein:
• R7 is C1-6 [18F]fluoroalkyl;
• and,
• Y2 is S, SO, SO2, or CH2.

A precursor for of Formula Ia

• wherein:
• X11 and X12 are independently selected from hydrogen, halogen, C1-6 alkoxy, C1-6 alkyl;
• R14 is hydrogen, C1-6 alkyl, C1-6 alkanoyl, C1-6 cycloalkyl, C1-6 fluoroalkyl, hydroxy, or halogen;
• Y11 is S, SO, SO2, or CH2
• R15 is the group —(CH2)o—C(═O)—NR11R12 wherein o is 0 to 10, and R11 and R2 are independently selected from C1-6 alkyl, C1-6 aminoalkyl, C1-6 alkoxyalkyl, C1-6 alkoxy, C1-6 hydroxyalkyl, a polyethylene glycol (PEG) group, C3-10 cycloalkyl, C3-10 cycloethers, and C3-10 cycloamines;
• and,
• R16 is hydrogen, and
• R13 is selected from an alkyl bromide, alkyl mesylate or alkyl tosylate.

A kit comprising a precursor of Formula Ia

• wherein:
• X11 and X12 are independently selected from hydrogen, halogen, C1-6 alkoxy, C1-6 alkyl;
• R14 is hydrogen, C1-6 alkyl, C1-6 alkanoyl, C1-6 cycloalkyl, C1-6 fluoroalkyl, hydroxy, or halogen;
• Y11 is S, SO, SO2, or CH2;
• R15 is the group —(CH2)o—C(═O)—NR11R12 wherein o is 0 to 10, and R11 and R2 are independently selected from C1-6 alkyl, C1-6 aminoalkyl, C1-6 alkoxyalkyl, C1-6 alkoxy, C1-6 hydroxyalkyl, a polyethylene glycol (PEG) group, C3-10 cycloalkyl, C3-10 cycloethers, and C3-10 cycloamines;
• R16 is hydrogen, and
• R13 is selected from an alkyl bromide, alkyl mesylate or alkyl tosylate.