A compound 15, wherein Ra, {HEAD ~ Rb} and {TAIL ~ Rc} are each hydrogen 
A compound 15 , wherein Ra , { HEAD ~ Rb } and { TAIL ~ Rc } are each hydrogen
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH