{HEAD ~ R10} is independently selected from the group consisting of H, alkyl, and {TAIL ~ arylalkyl} 
{ HEAD ~ R10 } is independently selected from the group consisting of H , alkyl , and { TAIL ~ arylalkyl }
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL