The present invention relates to (S)-2-[4-(4-chlorobenzhydryl)piperazin-1-yl]-ethoxyacetamide-(S)-pyrrolid- one-5-carboxylic acid salt; (R)-2-[4-(4-chlorobenzhydryl)piperazin-1-yl]-ethoxyacetamide-(S)-pyrrolid- one-5-carboxylic acid salt; (S)-2-[4-(4-chlorobenzhydryl)piperazin-1-yl]-ethoxyacetamide-(R)-pyrrolid- one-5-carboxylicacid salt; or (R)-2-[4-(4-chlorobenzhydryl)piperazin-1-yl]-ethoxycetamide-(R)-pyrrolido- ne-5-carboxylic salt. The present invention relates also to a process for preparing (S)-2-[4-(4-chlorobenzhydryl)piperazin-1-yl]-ethoxyacetamide (I) and (R)-2-[4-(4-chlorobenzhydryl) piperazin-1-yl]-ethoxyacetamide (II) by chemical resolution of a mixture. These compounds are respectively intermediates for the synthesis of dextrocetirizine and levocetirizine. ##STR00001##