These compounds comprise a moiety which provides a detectable species when released from {TAIL ~ the compound} in {HEAD ~ an environment} of pH 9 or less  
These compounds comprise a moiety which provides a detectable species when released from { TAIL ~ the compound } in { HEAD ~ an environment } of pH 9 or less
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH