or Q and {HEAD ~ R2 D} together form {TAIL ~ the group} ##STR19## wherein R18 is ##STR20## R16 and R17 are independently selected from the group consisting of CH2 , CH , C , 
together form
or Q and { HEAD ~ R2 D } together form { TAIL ~ the group } # # STR19 # # wherein R18 is # # STR20 # # R16 and R17 are independently selected from the group consisting of CH2 , CH , C ,
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL 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 OTH OTH OTH OTH OTH OTH