e bond coupling step illustrated in reaction Scheme A. As shown in Reaction Scheme J, treatment of an ethanol solution of carboxylic acid 39, wherein R is hydrogen, C1-C6 alkyl or C1-C3 polyfluoroalkyl, with a chlorinating agent such as thionyl chloride at a temperature of 65-78??? C., preferably 78??? C., for a period of 12-24 hours gives the corresponding ethyl ester derivative 40.