2-Pyridyl-2-thiazoline-4-carboxylic acid derivatives

A 2-(3'hydroxy-pyrid-2'-yl)-2-thiazoline-4-carboxylic acid derivative of the formula ##STR7## in a racemic or optically active form, in which R.sub.1 represents free hydroxy, hydrocarbyloxy, hydrocarbylcarbonyloxy or hydrocarbyloxycarbonyloxy, hydrocarbyl denoting an aliphatic radical having 1-7 carbon atoms, a cycloaliphatic radical having 3 to 8 ring members, a phenyl radical, or an aliphatic radical having 1-7 carbon atoms that is substituted by at least one cycloaliphatic radical having 3 to 8 ring members or by at least one phenyl radical, or in which R.sup.1 represents monocyclic aromatic or lower aliphatic sulphonyloxy;

• R.sup.2 represents hydrogen, an aliphatic radical having 1-7 carbon atoms, a cycloaliphatic radical having 3 to 8 ring members, a phenyl radical or an aliphatic radical having 1-7 carbon atoms that is substituted by at least one cycloaliphatic radical having 3 to 8 ring members or by at least one phenyl radical;
• and R.sup.3 represents hydrogen or lower alkyl;
• or a salt of such a derivative or a heavy metal ion complex of said derivative having a free 4-carboxy group.