provided that at least one of R3, R6 or {HEAD ~ R8} is {TAIL ~ SO3 X}; and 
is
provided that at least one of R3 , R6 or { HEAD ~ R8 } is { TAIL ~ SO3 X } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH