and t butyl the preferred r u2032 c 1 4 alkyl group is ethyl the preferred r u2033 c 1 4 alkyl group is ethyl or methyl and the preferred r u2032 u2033 c 1 4 alkyl group is ethyl or methyl scheme i below summarizes the three stages of the novel synthetic pathway used to prepare eprosartan according to scheme i 2 n butyl 4 formylimidazole is treated with a base such as 1 8 diazabicyclo 5 4 0 undec 7 ene dbu or 1 1 3 3 tetramethylguanidine followed by reaction with a regioselective nitrogen protecting reagent such as methyl acrylate ethyl acrylate acetyl bromide chloromethyl pivalate pom cl or di tert butyl dicarbonate to give derivatization on the least hindered nitrogen atom of the imidazole ring this reaction can be carried out in ethyl acetate acetonitrile toluene dmf thf or 1 methyl 2 pyrrolidinone nmp preferably this reaction is carried out using dbu and methyl acrylate or ethyl acetate in ethyl acetate at 50 60 u00b0 c typically the scheme i 1 compound is then reacted with 2 thienylmethyl propanedioic acid monothyl ester in a suitable solvent such as toluene acetonitrile dmf thf nmp or dmso in the presence of a catalyst for example in the presence of piperidine or piperidinium propionate in excess propionic acid at a suitable temperature such as a temperature of about 70 u00b0 c to about 100 u00b0 c preferably this reaction is carried out using piperidine in toluene at a reflux temperature of 65 u00b0 c 70 u00b0 c this reflux temperature is obtained by placing the reaction mixture under reduced pressure the quaternary salt of the scheme i 2 compound is then prepared by reacting this compound with a benzyl halide such as methyl or ethyl 4 bromomethyl benzoate.