R7, R8, and {HEAD ~ R10} are each, independently, alkyl of 1 6 carbon atoms, aralkyl of {TAIL ~ 7 10 carbon atoms}, fluorenylmethyl, or phenyl which is optionally mono , di , or tri substituted with a substituent selected from alkyl of 1 6 carbon atoms, alkoxy of 1 6 carbon atoms, hydroxy, cyano, halo, nitro, carbalkoxy of 2 7 carbon atoms, trifluoromethyl, amino, or CO2 H 
R7 , R8 , and { HEAD ~ R10 } are each , independently , alkyl of 1 6 carbon atoms , aralkyl of { TAIL ~ 7 10 carbon atoms } , fluorenylmethyl , or phenyl which is optionally mono , di , or tri substituted with a substituent selected from alkyl of 1 6 carbon atoms , alkoxy of 1 6 carbon atoms , hydroxy , cyano , halo , nitro , carbalkoxy of 2 7 carbon atoms , trifluoromethyl , amino , or CO2 H
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH