{HEAD ~ Substituents} with {TAIL ~ a specified function}, for example those that impart water solubility to the compound, may be included at any of R1 R6 
with
{ HEAD ~ Substituents } with { TAIL ~ a specified function } , for example those that impart water solubility to the compound , may be included at any of R1 R6
HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL 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