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