{HEAD ~ R8} is {TAIL ~ H}, OH, alkoxy, phenoxy, benzyloxy, ##STR18## NR4 R5, lower alkyl, phenyl or R3 phenyl; R9 is O , CH2 , NH or N  
is
{ HEAD ~ R8 } is { TAIL ~ H } , OH , alkoxy , phenoxy , benzyloxy , # # STR18 # # NR4 R5 , lower alkyl , phenyl or R3 phenyl ; R9 is O , CH2 , NH or N
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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH