GB779500A - Improvements in or relating to esters of acylated 3,5-diaminotriiodobenzoic acid - Google Patents

Abstract

The invention comprises compounds of the general formula <FORM:0779500/IV(b)/1> wherein R is an alkyl group containing from 1 to 6 carbon atoms, and R1 and R11 are alkanoyl groups, which may be the same or different, containing from 1 to 6 carbon atoms, and their preparation by acylation of the corresponding diamino compounds or, when the group R1 and R11 are different, the corresponding monoamino-monoacylamino compounds. The acrylation is carried out by heating with the appropriate acid, acid anhydride or acid halide. It is pre-ferable to use formic acid for the formation of the formyl derivative and the appropriate acid anhydride or acid halide for the formation of higher derivatives. The acylation is promoted by the addition of a trace of a strong acid such as sulphuric acid, perchloric acid or an organic sulphonic acid. Examples describe the preparation of (1) the ethyl, methyl, propyl, isopropyl and butyl esters of 3,5-diacetamino-2,4,6-triiodobenzoic acid by acrylation of the corresponding esters of 3,5-diamino-2,4,6-triiodobenzoic acid with acetic anhydride in the presence of a trace of concentrated sulphuric acid; (2) ethyl 3,5-diformamido-2,4,6-triiodobenzoate by heating the corresponding diamino compound with formic acid; (3) ethyl 3,5-dipropionamido-2,4,6-triiodobenzoate by heating the corresponding diamino compound with propionic anhydride or propionyl chloride; the butyramido compound is obtained similarly; (4) ethyl-3-formamido-5-acetamino - 2,4,6 - triiodobenzoate by heating ethyl 3 - amino - 5 - acetamido - 2,4,6 - triiodo benzoate with formic acid; and (5) ethyl 3-propionamido - 5 - acetamido - 2,4,6 - triiodobenzoate by heating ethyl 3-amino-5-acetamido-2,4,6-triiodobenzoate with propionic anhydride. The products are stated to be useful as X-ray contrasting agents. Starting materials. Esters of 3,5-diamino-2,4,6-triiodobenzoic acid are prepared by catalytic reduction of the corresponding ester of 3,5-dinitrobenzoic acid followed by exhaustive iodination of the resulting 3,5-diamino benzoic acid ester with iodine monochloride in acid solution. Esters of 3-amino-5-acylamino-2,4,6-triodobenzoic acid are prepared as follows: 3,5-dinitrobenzoic acid is selectively reduced to 3-nitro-5-amino-benzoic acid which is then acylated to a 3-nitro-5-acylaminobenzoic acid. This is then esterified and the ester is catalytically hydrogenated to give an alkyl 3-amino-5-acrylamino benzoate which is exhaustively iodinated, conveniently with a solution of potassium iodide dichloride (KIbl2).ALSO:A radiopaque agent contains as an active ingredient a compound of the formula <FORM:0779500/VI/1> where in R is an alkyl group containing from 1 to 6 carbon atoms and R1 and R11 are the same or different alkanoyl groups each containing from 1 to 6 carbon atoms. The active ingredient may be dispersed in a finely divided dust or it may be made into an aqueous suspension with the aid of an emulsifying agent such as carboxymethylcellulose, polyvinyl-pyrrolidone or dextran.