Diastereomeric 7-ureidoacetyl cephalosporins. I. Superiority of 7alpha-H-L-isomers over D-isomers.

The synthesis and in vitro structure-activity relationship of 7-ureidoacetyl cephalosporins carrying various substituents in the 3-position, compounds that showed an enhanced broad spectrum of antibacterial activity, has been outlined. Contrary to most of the previous observations with diastereomeric isomers of cephalosporins, it has been found that the L-side chain isomers also are very potent antibiotics and are even more active inhibitors of certain beta-lactamase-producing Gram-negative bacteria than the corresponding D-side chain isomers. SQ 69,613, 7beta-[[L-[(aminocarbonyl)amino]-2-furanylacetyl]amino]-3-[[(1-methyl-1H-tetrazol-5-yl) thio]methyl]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid, sodium salt, the most active compound tested, except for activity against staphylococci, was as active in vitro as cefamandole.