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