Quinone-masked probes as labeling reagents for cell uptake measurements

A compound of formula (I), or a salt thereof,

• wherein
• A is a reporter moiety;
• R14 is H, alkyl, hydroxyalkyl, alkoxy, carboxyalkyl, or amidoalkyl;
• R9 and R10 are independently selected from alkyl;
• R11, R12 and R13 are independently selected from H, alkyl, alkoxy, bromo, chloro or amino, or R11 and R12 can form a fused phenyl ring;
• X is O;
• L is —(CH2)mC(R17)2(CH2)n—Y—C(O)—;
• R17 is independently H, alkyl or both R17 together can form an alkyl ring having from 3-7 carbons;
• m is an integer from 0-2;
• n is an integer from 0-2;
• Y is O or NR15;
• R15 is H, alkyl, hydroxyalkyl, azidoalkyl, cyanoalkyl, haloalkyl, alkenyl, alkynyl, -alkyl-N(R23)C(O)R24, -alkyl-SO3R25, -alkyl-SO2N(R26)(R27), -alkyl-COR28, -alkyl-CO2R29, -alkyl-OC(O)R29, -alkyl-OC(O)N(R30)(R31), -alkyl-amide, or polyalkoxyalkyl, wherein the polyalkoxyalkyl and -alkyl-amide are unsubstituted or substituted with one or more suitable substituents;
• and
• R23, R24, R25, R26, R27, R28, R29, R30, and R31 are each independently selected from hydrogen, alkyl, aryl, heteroaryl, heterocyclyl, and cycloalkyl.