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