{HEAD ~ R5} represents {TAIL ~ carboxy}; and the carbon atoms marked by and are in R or S configuration 
represents
{ HEAD ~ R5 } represents { TAIL ~ carboxy } ; and the carbon atoms marked by and are in R or S configuration
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH