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