Patent ID: 6984718

Claim:
A compound having the following structural formula: or a biologically acceptable salt or pro-reporter molecule thereof, wherein: X is a peptide comprising aspartic acid and an N-terminal protecting group; R 8 and R 9 are each independently selected from the group consisting of hydrogen, alkyl and aryl; R 10 and R 11 are each independently selected from the group consisting of hydrogen and alkyl; R 1 -R 5 are each independently hydrogen, fluoro, chloro, bromo, iodo, haloalkyl, aryl, cycloalkyl, alkyl, alkenyl, alkynyl, aralkyl, aralkenyl, aryl alkynyl, hydroxyalkyl, nitro, amino, cyano, acylamino, acyl, hydroxy, acyloxy, alkoxy, alkylthio, and carboxy; provided that at least one of R 1 , R 3 and R 5 is selected from the group consisting of fluoro and chloro; and provided that said N-terminal protecting group is not an acetyl group.