R7, R8, and R10 are each, independently, alkyl of 1 6 carbon atoms, aralkyl of 7 10 carbon atoms, fluorenylmethyl, or phenyl which is optionally mono , di , or tri substituted with {HEAD ~ a substituent} selected from {TAIL ~ 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 
selected from
R7 , R8 , and R10 are each , independently , alkyl of 1 6 carbon atoms , aralkyl of 7 10 carbon atoms , fluorenylmethyl , or phenyl which is optionally mono , di , or tri substituted with { HEAD ~ a substituent } selected from { TAIL ~ 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
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