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