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