Z is chosen from {TAIL ~ CR6} and {HEAD ~ CCOCNHR8}, wherein R6 is alykl, arylalkyl, aryl, m cycloalkyl, heteroaryl, or ##STR73## wherein m=0 3 
Z is chosen from { TAIL ~ CR6 } and { HEAD ~ CCOCNHR8 } , wherein R6 is alykl , arylalkyl , aryl , m cycloalkyl , heteroaryl , or # # STR73 # # wherein m=0 3
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH