{HEAD ~ R25} is hydrogen, alkyl of 1 6 carbon atoms, or {TAIL ~ aralkyl} of 7 10 carbon atoms 
is
{ HEAD ~ R25 } is hydrogen , alkyl of 1 6 carbon atoms , or { TAIL ~ aralkyl } of 7 10 carbon atoms
HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH