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