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