{HEAD ~ R6} is lower alkyl, {TAIL ~ phenyl}, R3 phenyl, benzyl or R3 benzyl 
is
{ HEAD ~ R6 } is lower alkyl , { TAIL ~ phenyl } , R3 phenyl , benzyl or R3 benzyl
HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH