The present invention provides a novel carbamazepine hydrazide compound suitable for covalent attachment to a polymer particle reagent, having the general formula ##STR1## The present invention also provides a novel carbamazepine acid compound suitable for attachment to proteins for the production of carbamazepine immunogens. The carbamazepine antigen of the present invention has the following general structure: ##STR2## where X is C.dbd.O, CH.sub.2 or SO.sub.2 ; Y is C.dbd.O, CH.sub.2, SO.sub.2 ; R is an alkyl and P is a protein or a hapten.
The present invention relates to a process for the preparation of N-phosphonomethyliminodiacetic acid by reacting an alkali metal salt of iminodiacetic acid with phosphorus trichloride in aqueous solution with formation of the hydrochloride of iminodiacetic acid, phosphorous acid and of the corresponding alkali metal chloride, followed by reaction with a formaldehyde source and, if desired, recovery of the N-phosphonomethyliminodiacetic acid from the reaction mixture, in which water, which may comprise HCl, is removed from the reaction mixture during and/or after reacting the alkali metal salt of iminodiacetic acid with phosphorus trichloride until the concentration of iminodiacetic acid hydrochloride is at least 40% by weight, based on the weight of the reaction mixture minus the weight of alkali metal chloride.The process makes possible the preparation of N-phosphonomethyliminodiacetic acid in a simple fashion and in high yield.
