{TAIL ~ R27} is alkyl of 1 6 carbon atoms, arylalkyl of 7 10 carbon atoms, allyl, fluorenylmethyl, or phenyl which is optionally mono , di , or tri substituted with a substituent selected from {HEAD ~ 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 
{ TAIL ~ R27 } is alkyl of 1 6 carbon atoms , arylalkyl of 7 10 carbon atoms , allyl , fluorenylmethyl , or phenyl which is optionally mono , di , or tri substituted with a substituent selected from { HEAD ~ 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
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 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH