Methods to activate the carboxylic acid include reacting said acid with one or more molar equivalents of oxalyl chloride or {HEAD ~ thionyl chloride} to afford {TAIL ~ the carboxylic acid chloride} in a suitable solvent such as dichloromethane, chloroform or diethyl ether 
Methods to activate the carboxylic acid include reacting said acid with one or more molar equivalents of oxalyl chloride or { HEAD ~ thionyl chloride } to afford { TAIL ~ the carboxylic acid chloride } in a suitable solvent such as dichloromethane , chloroform or diethyl ether
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 HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH