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