Acetylene derivatives and their use for binding and imaging amyloid plaques

A compound of Formula I,

• or a pharmaceutically acceptable salt thereof, wherein:
• A1 is CH
• A2 is CH or N;
• R1 and R2 are each independently:
• hydrogen, —NHC1-4alkyl, —N(C1-4alkyl)2, —NH2, C1-4alkoxy or —OH;
• R3 fragment i, ii or iii, wherein:
• fragment i is:
• wherein n is an integer from 1 to 10;
• m is an integer from 0 to 5;
• y is an integer from 0 to 5;
• R5 is hydrogen, C1-4 alkyl, or hydroxy(C1-4)alkyl;
• Ra, Rb, Rc, Rd, Re, Rf, Rg and Rh are each independently hydrogen, halogen, hydroxy, C1-4 alkoxy, C1-4 alkyl, or hydroxy(C1-4)alkyl;
• and
• Z is:
• a) X, wherein X is hydrogen, hydroxy, halogen, radiohalogen, C1-4 alkoxy, hydroxy(C1-4)alkyl, halo(C1-4)alkyl, radiohalo(C1-4)alkyl or NRxRy, wherein Rx and Ry are independently hydrogen, C1-4 alkyl, hydroxy(C1-4)alkyl, radiohalo(C1-4)alkyl or halo(C1-4)alkyl;
• b) one of the following groups, each of which contains X as a substituent:
• benzoyloxy, phenyl(C1-4)alkyl, aryloxy or C6-10 aryl;
• or
• c) Zc, having the following structure:
• wherein p is an integer from 1 to 4, Q is O or NR5 and G is —C═C—(RG)X or —C≡C—X, wherein RG is hydrogen or C1-4 alkyl, and Rn and Ro are independently hydrogen, hydroxyl or C1-4alkyl;
• fragment ii is:
• wherein y′is an integer from 0 to 5;
• and fragment iii is:
• wherein e is 0 or 1;
• R4 is hydrogen, halogen, or radiohalogen;
• provided that,
• if X is not or does not contain F or 18F, then R4 is F, 18F 123I, 125I, 131I, 76Br, or 77Br or Br.