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