Nycomed Imaging As

Amersham Health As

Odd Einar Ingvoldstad

Trygve Gulbrandsen

Lars Terje Holmaas

Espen Myrbrangten

Dick Malthe-So Slashedrensen

Process for the preparation of contrast agents The invention provides a process for the preparation of an N-alkyl-acylamino-phenyl-carboxylic acid or carboxylic acid derivative by liquid phase acylation and subsequent N-alkylation of a corresponding amino-phenyl-carboxylic acid (or carboxylic acid derivative), the improvement comprising the addition of an alkylating agent to a solution containing the reaction products of said acylation, to effect said N-alkylation.

Process for the preparation of contrast agents

The invention provides a process for the production of iohexol comprising reacting 5-acetamido-N,N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodophthalamide with a 2,3-dihydroxypropylating agent, the improvement comprising effecting that said process in the presence of a solvent comprising 2-methoxy-ethanol and, optionally, isopropanol.

Process for iohexol manufacture

The invention provides a process for the preparation of an N-alkyl-acylamino-phenyl-carboxylic acid or carboxylic acid derivative by liquid phase acylation and subsequent N-alkylation of a corresponding amino-phenyl-carboxylic acid (or carboxylic acid derivative), the improvement comprising the addition of an alkylating agent to a solution containing the reaction products of said acylation, to effect said N-alkylation.

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Oslo, Norway

Odd Einar Ingvoldstad