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