Dual-action cephalosporins incorporating a 3'-tertiary-amine-linked quinolone

We have previously reported that linking quinolones to the cephalosporin 3'-position through an ester bond, a carbamate function, or a bond through a quaternary nitrogen produced cephalosporins with a dual mode of antibacterial action. We now describe a new class of dual-action cephalosporins, with greater chemical stability than those previously reported, in which the basic nitrogen of ciprofloxacin is bonded directly to the 3'-cephalosporin position, i.e., the two moieties are linked through a tertiary amine function. These compounds have demonstrated potent activity against a broad spectrum of Gram-positive and Gram-negative bacteria, including beta-lactam-resistant strains.

Dual-action penems and carbapenems

Two new series of dual-action antibacterial agents were synthesized in which penems and carbapenems were linked at the 2'-position to quinolones through either an ester or a carbamate moiety. Potent, broad-spectrum antibacterial activity was observed for both classes of compounds, indicative of a dual-mode of action.

6 alpha-hydroxypenicillanic acid-S(S)-oxide and analogues: synthesis and antimicrobial activity

The synthesis and in vitro antibacterial activity of a series of 6-oxygenated penicillanic acid sulfoxides is described. 6 alpha-Hydroxypenicillanic acid-S(S)-oxide (1a) exhibits weak Gram-negative antibacterial activity and appears to be similar to amdinocillin (5) in its mode of action. 6 alpha-Hydroxypenicillanic acid-S(R)-oxide (4a) has a broader spectrum of activity, but again is rather weak. The corresponding 6 beta-hydroxy series is essentially devoid of activity.

Dual-action cephalosporins: cephalosporin 3'-quinolone carbamates

A series of cephalosporins has been prepared in which the 3'-position was linked to the nitrogen of the antibacterial quinolone ciprofloxacin through a carbamate function. Like the ester-linked and quaternary-linked dual-action cephalosporins reported earlier, these carbamate-linked compounds exhibited a broad antibacterial spectrum derived from both cephalosporin-like and quinolone-like activities, suggesting a dual mode of action. Studies to elucidate details of the mechanism of action have been inconclusive. Ciprofloxacin liberated as a consequence of bacterial enzyme-mediated reactions may contribute to the second mode of action, although some evidence indicates that the intact carbamate-linked bifunctional molecules may possess intrinsically both beta-lactam and quinolone activities.

Cephalosporin 3'-quinolone esters with a dual mode of action

According to the generally accepted mechanism by which bacterial enzymes react with cephalosporins, opening of the beta-lactam ring can lead to the expulsion of a 3'-substituent. A series of dual-action cephalosporins was prepared in which antibacterial quinolones were linked to the cephalosporin 3'-position through an ester bond in the expectation that, in addition to exerting their own beta-lactam activity, these cephalosporins would act as prodrugs for the second antibacterial agent. Compared to parent cephalosporins in which the 3'-substituent was acetoxy, the bifunctional cephalosporins exhibited a broadened antibacterial spectrum, suggesting that a dual mode of action may indeed be operative.

Antibacterial properties of (2,3)-alpha- and (2,3)-beta-methylene analogs of penicillin G

The penam nucleus can assume two conformations; these are designated open and closed. The synthetic (2,3)-alpha- and (2,3)-beta-methylenepenams can be regarded as analogs of the open and closed conformations, respectively. It has been shown that the beta-methylenepenams are essentially inactive, suggesting that the closed conformation of penams is also inactive. In this study, we investigated a series of beta-lactams, all of which contained phenylacetamido side chains: penicillin G, the (2,3)-alpha- and (2,3)-beta-methylenepenams, and the 3-acetoxymethyl- and 3-methylcephalosporins. The alpha-methylenepenam and penicillin G were the most active compounds, while the beta-methylene isomer was only poorly active. Results with permeability mutants suggested that the alpha-methylene compound penetrated the outer membrane somewhat more readily than penicillin G did. The intrinsic potency of the alpha-methylenepenam appeared to be similar to that of penicillin G, on the basis of their affinities for penicillin-binding proteins and their abilities to inhibit peptidoglycan synthesis in ether-permeabilized Escherichia coli, while the beta-methylene analog had very poor intrinsic potency. The alpha-methylene analog was about 10-fold more efficient (Vmax/Km) than penicillin G as a substrate for the cephalosporinases from Enterobacter cloacae and Proteus vulgaris, but it was about 40-fold less efficient with penicillinase from Staphylococcus aureus. These results strongly support the hypothesis that the active conformation of penams is the open conformation and suggest that the position in space of the carboxyl group relative to the beta-lactam carbonyl is an important determinant of cephalosporinlike character, as distinct from penicillinlike character.

Ro 22-5417, a new clavam antibiotic from Streptomyces clavuligerus. III. Absolute stereochemistry

The complete stereostructure of the new antibiotic Ro 22-5417 has been established as 3-[(3S,5S)-7-oxo-1-aza-4-oxabicyclo[3.2.O]hept-3-yl]-L-alanine. This result together with the synthesis of an (3R,5R)-L-analog allowed us to postulate that clavams require the R-configuration at the ring juncture for beta-lactamase inhibitory activity, while the opposite S-stereochemistry is essential for antifungal activity.

Ro 22-5417, a new clavam antibiotic from Streptomyces clavuligerus. I. Discovery and biological activity

Streptomyces clavuligerus NRRL 3585, a culture which produces a variety of beta-lactam antibiotics in the penicillin, cephalosporin and clavam families, was found to produce a new beta-lactam antibiotic, Ro 22-5417. The compound, which was neither a substrate for nor inhibitor of several beta-lactamases, showed antimicrobial activity in defined minimal medium but little or no inhibitory activity in nutrient-rich medium. The activity was bacteriostatic against Bacillus species ATCC 27860 and was antagonized by D- and L-methionine, L-cystathionine, L-homocystine and O-acetyl-L-homoserine but not by L-homoserine, L-aspartate, L-cysteine or other common amino acids, vitamins and nucleosides. Our results are consistent with Ro 22-5417 acting as an inhibitor in methionine biosynthesis.

A new semisynthetic macrolide antibiotic 3-O-oleandrosyl-5-O-desosaminylerythronolide A oxime

A new antibiotic, 3-O-oleandrosyl-5-O-desosaminylerythronolide A oxime (3) was produced from erythronolide A oxime (1) by the oleandomycin-producing culture, Streptomyces antibioticus ATCC 11891. The structure of 3 was determined by degradative studies and confirmed by X-ray analysis. Compound 3 was found to be less active, but more stable to acid, then erythromycin A oxime.

Antimetabolites produced by microorganisms. XIII. The synthesis and microbiological production of a novel amino acid, L-2-amino-4-(2-aminoethoxy) butanoic acid

A novel amino acid, L-2-amino-4-(2-aminoethoxy-)-butanoic acid, was isolated from a fermentation broth of Streptomyces sp. X-11,085. It was shown to be identical with the chemical reduction product of an antimetabolite antibiotic, L-2-amino-4-(2-aminoethoxy)-trans-3-butenoic acid, a co-product in the fermentation. Addition of the title compound to the fermentation led to an enhanced yield of the antimetabolite suggesting that the saturated amino acid serves as a precursor for the antimetabolite.

Penicillin acyltransferase in Penicillium chrysogenum

Isotopic exchange of (35)S between penicillins and 6-amino-penicillanic acid (6-APA) was observed in cell-free extracts of Penicillium chrysogenum. Sulfhydryl-containing compounds were required for activity. Dithiothreitol, dithioerythritol, mercaptoethanol, and glutathione served as activators. The acyltransferase was purified threefold by adsorption on calcium phosphate gel at pH 6 and elution at pH 8. The partially purified enzyme showed maximal activity at pH 8. The enzyme was stable at 25 C for at least 30 min at pH 8. Dissociable inhibitors or activators, other than the sulfhydryl-containing compounds, could not be demonstrated in the enzyme preparation. An apparent Michaelis constant of 1.5 +/- 0.5 mm was determined for penicillin G at a 6-APA concentration of 5 mm. The enzyme did not appear to possess penicillin amidase activity. The exchange mechanism probably involves an acyl-enzyme intermediate. Penicillins V, G, K, X, and dihydro F showed isotopic exchange with (35)S-6-APA. Penicillin N, methylpenicillin, and phenyl-penicillin did not show exchange. The level of acyltransferase in P. chrysogenum 51-20F3 was measured at times during the fermentation. The level of activity increased threefold between 40 and 55 hr, remaining high until about 90 hr.