Abstract: Compounds according to general formulae (Ia to Ie) wherein: X?O or S; Y is O, S or CH2, CHR, CRR, where R is C1-7 alkyl; Z is O or S; R1 is H or C1-7 alkyl; R2 is H or C1-7 alkyl; R4 is H or C1-7 alkyl at any vacant position on the aromatic ring; R3 is C1-7 alkyl-L1-R5-L2-R6—COOH, C3-10 cycloalkyl-L1-R5-L2-R6—COOH or Ar—C0-7 alkyl-L1-R5-L2-R6—COOH; each of L1 and L2 is absent or a suitable linker such as an amide CONH; or an ether —O—, or a thioether —S— or a sulphone —SO2—; R5 is C1-7 alkyl, C3-10 cycloalkyl or Ar—C0-7 alkyl each of which is substituted with either NR8R9, where the nitrogen atom is capable of being protonated in solution to give N+HR8R9; or a quaternary nitrogen atom N+R8R9R10, such that R5 contains a positive charge; each of R8, R9 and R10 is independently C1-7 alkyl, C3-10 cycloalkyl or Ar—C0-7 alkyl, or any two or more of R8, R9 and R10 together form an alicyclic or arylalicyclic ring system; R6 is C1-7 alkyl, C3-10 cycloalkyl or Ar—C0-7 alkyl; and their salts, hydrates, solvates, complex

Abstract: A process is provided for the assessment of an active proteolytic enzyme in a blood or another biological fluid sample possibly comprising a complex of said proteolytic enzyme and &agr;2-macroglobulin, wherein said sample is contacted with a substrate comprising a molecule of sufficient size coupled to a signal-substrate, said signal-substrate comprising a detectable leaving group, wherein said substrate is hydrolysed by said proteolytic enzyme but not by said complex. The proteolytic enzyme is preferably selected from the group consisting of thrombin, activated clotting factor, activated fibrinolytic factor, and activated component of the complement system. Of these, thrombin is most preferred. The molecules of sufficient size are preferably water soluble and selected from the group consisting of inert protein, preferably ovalbumin, polysaccharide, and synthetic polymer. The size of these molecules is such that they will not fit into the cavity of the &agr;2M molecules.