R7 is {HEAD ~ H}, {TAIL ~ alkyl}, arylalkyl, or n cycloalkyl; and 
R7 is { HEAD ~ H } , { TAIL ~ alkyl } , arylalkyl , or n cycloalkyl ; and
OTH OTH HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH