R23 and R26 are each independently hydrogen, formyl, {HEAD ~ alkanoyl} of {TAIL ~ 2 7 carbon atoms}, arylalkanoyl of 8 11 carbon atoms, aryloyl, or CO2 R27  
of
R23 and R26 are each independently hydrogen , formyl , { HEAD ~ alkanoyl } of { TAIL ~ 2 7 carbon atoms } , arylalkanoyl of 8 11 carbon atoms , aryloyl , or CO2 R27
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH