Process for the production of 3-hydroxy compounds

Process for the production of 7.beta.-substituted 3-hydroxy-cepham-4-carboxyic acid compounds of the formula ##STR6## in which R.sub.1.sup.a represents hydrogen or an amino-protecting group R.sub.1.sup.A, and

• R.sub.1.sup.b represents hydrogen or an acyl radical Ac having up to 18 carbon atoms or in which
• R.sub.1.sup.a and R.sub.1.sup.b together from a bivalent acyl radical of an organic dicarboxylic acid having up to 18 carbon atoms, and
• R.sub.2 represents a radical that, together with the carbonyl grouping --C(=O)--, forms a protected carboxyl group,
• and 1-oxides thereof as well as salts of such compounds with salt-forming groups, from a 7.beta.-substituted 3-hydroxy-3-cephem-4-carboxylic acid compound of the formula ##STR7## from a 1-oxide or a salt thereof, and a complex borohydride selected from the group consisting of an alkali metal borohydride, zinc borohydride, or such borohydride wherein from one to three hydrogen atoms are replaced by cyano, alkanoyloxy, halogenated alkanoyloxy, benzoyloxy, or lower alkoxy, characterized in that the reduction is carried out in the presence of an organic acid selected from the group consisting of an aliphatic, cycloaliphatic or aromatic carboxylic acid having up to 18 carbon atoms, which may be substituted by halogen, lower alkoxy, phenyl, or nitro.