Chemiluminescence probes for tuberculosis

A compound of the formula Ia or Ib:

• wherein
• R1 is selected from the group consisting of (C1-C18)alkyl and (C3-C7)cycloalkyl;
• R2 and R3 each independently is selected from the group consisting of a branched (C3-C18)alkyl and (C3-C7)cycloalkyl, or R2 and R3 together with the carbon atom to which they are attached form a fused, spiro or bridged cyclic or polycyclic ring;
• R4 is H, or halogen attached either ortho or para to the —O-L-Pep group;
• A is a π* acceptor group of the formula
• attached either ortho or para to the —O-L-Pep group, wherein r is an integer of 1 to 6, and E is:
• (a) —CN, —COOH, or —COO(C1-C18)alkyl optionally interrupted in the alkylene chain with one or more —O— groups or substituted with one or more groups each independently selected from the group consisting of —OH, —COOH, halogen, and —NH2;
• (b) a group of the formula
• denoting a mono- or polycyclic, aromatic or nonaromatic ring system comprising the moiety
• respectively, as a ring member, and linked to the alkenylene chain of group A via any atom which is a member of said mono- or polycyclic, aromatic or nonaromatic ring system, provided that a delocalized x-system extends from the nitrogen atom of
• via the alkenylene chain of group A to the central aromatic ring of the compound of formula Ia or Ib,
• wherein said mono- or polycyclic, aromatic or nonaromatic ring system is optionally substituted with one or more groups each independently selected from the group consisting of halogen, —OH, —CN, —SO3H or a salt thereof, —COOH or a salt thereof, —COO—(C1-C18)alkyl, (C1-C6)alkyl, (C2-C6)alkenyl, (C2-C6)alkynyl, a polyethylene glycol chain, and a polypropylene glycol chain, and
• wherein R5 is H, —O−, (C1-C8)alkyl, (C2-C8)alkenyl, or (C2-C8)alkynyl, wherein said (C1-C8)alkyl, (C2-C8)alkenyl and (C2-C8)alkynyl each is optionally substituted with one or more groups each independently selected from the group consisting of —OH, —COOH, halogen, and —NH2, and optionally interrupted with one or more —O— or —CO— groups;
• or
• (c) a group of the formula
• linked to the alkenylene chain of group A via a carbon atom of the pyrylium moiety,
• wherein R6 and R7 each independently is selected from the group consisting of H, (C1-C6)alkyl, (C2-C6)alkenyl, (C2-C6)alkynyl, and (C3-C7)cycloalkyl;
• L is a linker of the formula:
• optionally substituted at the aromatic or heteroaromatic ring with one or more substituents each independently selected from the group consisting of (C1-C18)alkyl and (C3-C7)cycloalkyl, wherein X is S, O, or NR8;
• R8 each independently is H or (C1-C18)alkyl;
• and the asterisk represents the point of attachment to the group Pep;
• and
• Pep is a Mycobacterium tuberculosis (Mtb)-specific protease cleavable peptide linked via a carboxylic group thereof and optionally acetylated at its alpha amino acid.