{HEAD ~ R7} is {TAIL ~ H}, alkyl, arylalkyl, or n cycloalkyl; and 
{ HEAD ~ R7 } is { TAIL ~ H } , alkyl , arylalkyl , or n cycloalkyl ; and
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH