{HEAD ~ A} is halogen, phenyl, {TAIL ~ Sm phenyl}, or NR5R6 
is
{ HEAD ~ A } is halogen , phenyl , { TAIL ~ Sm phenyl } , or NR5R6
HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH