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