The synthesis and the antibacterial activity of 7;2-[D-2-[(4-hydroxy-1,5-naphthyridine-3carbonylamino)-and (4-hydroxypyridine-3-carbonylamino)]-2-(4-hydroxyphenyl)acetamido]cephalosporins with various substituents at the 3-position in the cephem nucleus are described. These compounds exhibited strong antibacterial activities against a variety of Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa and Enterobacter aerogenes, which are insensitive to cefazolin and cefmetazole. The compounds (3e, 4e) having a 1-methyl-I H-tetrazolylthiomethyl group at the 3-position appeared to show the best activity in each series. The 4-hydroxypyridine-3-carbonylamino derivative 4e gave higher peak serum concentrations and urinary recovery rates than those of the 4-hydroxy-1,5-naphthyridine derivative 3e when administered subcutaneously to mice and intramuscularly to rats.

The 4-methoxybenzyloxycarbonyl group of 7-[d-2-(4-hydroxyphenyl)-2-(4-methoxybenzyloxycarbonylamino)acetamido]cephalosporanic acid was effectively removed with p-toluenesulfonic acid in acetonitrile. The mechanism of the deprotection is discussed and the role of acetonitrile can reasonably be explained in terms of the Ritter reaction.

The influence of the chirality of the 7-acyl side chain and of various N-acyl moieties (A-CO-) on the in vitro activity of 7(3-[2-acylamino-2-(4-hydroxyphenyl)acetamido]-3-[(1-methyl-1 H-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxylic acids (6) was investigated. A cephalosporin having a 7-acyl side chain of S-configuration (6r) was only weakly active against Staphylococcus aureus and Klebsiella pneumoniae and was inactive against the other species tested. Among the various N-acyl moieties in the cephalosporins having a 7-acyl side chain of the R-configuration, the 4-hydroxypyridine-3-carbonyl moiety, unsubstituted or substituted with 5-bromo and/or 6-alkyl groups and the 4-hydroxy-l,5-naphthyridine-3-carbonyl moiety, unsubstituted or substituted with a 6-methyl and a 6-methoxy group gave the most active compounds.NEthylation of the 4-hydroxy-l,5-naphthyridine-3-carbonyl derivative and the 4-hydroxypyridine-3-carbonyl derivative (6p, 6q) resulted in a decrease of the in vitro activity.In the preceding paper'', we reported the synthesis and the antibacterial activity of 7j3-[D-2-[(4 hydroxy-1,5-naphthyridine-3-carbonylamino)-and (4-hydroxypyridine-3-carbonylamino)]-2-(4-hydroxyphenyl)acetamido]cephalosporins.The compounds showed high antibacterial activity against a variety of Gram-positive and Gram-negative bacteria including Pseudomonas aeruginosa and Enterobacter aero genes. The results showed that the N-acyl moieties (A-CO-, see general formulas 6) and the 3-substituents of the cephalosporins had important effects on the antibacterial activity, spectrum, and pharmacokinetic characteristics of the compounds.We report here the synthesis and the antibacterial activity of cephalosporins having acyl moieties other than 4-hydroxy-1,5-naphthyridine-3-carbonyl and 4-hydroxypyridine-3-carbonyl residues. In this study, we selected the 1-methyl-IH-tetrazol-5-ylthiomethyl group as the 3-substituent because in the preceding study it was the most effective one in increasing the in vitro activity of the compounds. ChemistryThe cephalosporins listed in Table 1 were prepared by one of the methods outlined in Scheme 1.A general procedure for the acylation of 5R with N-hydroxysuccinimide esters (Method A) was described in our preceding paper.') The procedure for the acylation of 5R with p-nitrophenyl esters (Method B) was the same as Method A except for using p-nitrophenyl esters instead of N-hydroxysuccinimide esters. The acylation of 5R with acid chloride (Method C) was performed as described in the experimental section.

The influence of various 3-substituents on the antibacterial activity of 7J3-[D-2-(4-hydroxy-6-methylpyridine-3-carbonylamino)-2-(4-hydroxyphenyl)acelamido]ceph-3-em-4-carboxylic acids (III) was investigated. Introduction of an acidic substituent, such as a sulfo or a carboxyl group, to a 3-(1-methyl-lH-tetrazolyl)thiomethyl substituent (IJ f-i) resulted in a marked loss of activity against Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, Escherichia coli, Klebsiella pneumoniae, and Enterobacter aerogenes, in contrast to an in crease of activity against Proteus mirabilis. Displacement of the acetoxy group of IIIb with pyridines (111m-p) enhanced the activity against P. aeruginosa and E. aerogenes: their activity against those strains were superior to that of the cephalosporin IIId having a 3-(1-methyl-IH-tetrazolyl)thiomethyl substituent. As a result of extensive studies in addition to the study of in vitro activity in this series, 7~-[D-2-(4-hydro);y-6-methylpyridine-3-carbonylamino)-2-(4-hydroxyphenyl)acetamido]-3-[(1-methyl-I H-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxylic acid, code No. SM-1652, cefpiramide (generic name), was selected as a candidate for further biological and clinical investigations. In a preceding papery, we reported the study of the influence of various N-acyl moieties on the antibacterial activity of 748-[2-acylamino-2-(4-hydroxyphenyl)acetamido]-3-[(1-methyl-lH-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxylic acids. This property as well as the pharmacokinetic characteristics of the compounds may, however, also be influenced by the nature of the 3-substituents of the cephem nucleus. We report here a study on the influence of various 3-substituerts on the antibacterial activity of this type of cephalosporin. The 4-hydroxy-6-methylpyridine-3-carbonyl group, which has been found favorably affect the activities of the cephalosporins'), was chosen as the N-acyl moiety. Chemistry The cephalosporins listed in Table I were prepared by the two general methods outlined in Scheme 1. Only cephalosporins having the R-configuration of the chiral center of the 7jS-side chain were prepared because a preceding investigation') had demonstrated that in at least one case the corresponding S-epimer has inferior biological activity. The general synthetic procedures (Methods A and B) were the same as those described in a previous report') except for the preparation of IIIm-p, which were obtained by displacing the acetoxy group of THE JOURNAL OF ANTIBIOTICS