{HEAD ~ R7} is OH, {TAIL ~ lower alkyl}, phenyl, benzyl, R3 phenyl or R3 benzyl 
{ HEAD ~ R7 } is OH , { TAIL ~ lower alkyl } , phenyl , benzyl , R3 phenyl or R3 benzyl
HEAD HEAD HEAD HEAD HEAD REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH