Frederick T. Counter

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The novel lipopeptide antibiotic A21978C complex is active against Gram-positive organisms. This complex consists of a common peptide nucleus with various lipid acyl groups at the N-terminus characteristic of each individual factor. The fatty acid acyl group is removed by incubation of the A21978C complex with Actinoplanes utahensis to give the peptide(More)
A novel low-molecular weight inhibitor of an aminoglycoside-inactivating enzyme, initially isolated from fermentation broths of Streptomyces neyagawaensis, was determined to be 7-hydroxytropolone. Its structure was confirmed by synthesis. In vitro synergy was demonstrated between 7-hydroxytropolone and certain aminoglycosides against bacteria which were(More)
Although a substantial number of 16-membered macrolides related to tylosin have now been isolated and evaluated as antibiotics, none appeared to be superior to tylosin in treating bacterial or mycoplasmal infections caused by sensitive organisms. Nevertheless, this comparison of the antibiotic activity of 16-membered macrolides clearly indicates that novel(More)
Studies of susceptibility, development of resistance, and synergy were performed with 32 antimicrobics againstClostridium difficile strains. A microtiter technique was used to demonstrate the in vitro activities of 40C. difficile isolates. Rifampin inhibited 73% of the strains at a concentration of ≤0.06 μg/ml, and metronidazole inhibited 90% at 0.5 μg/ml.(More)
Dirithromycin is a 9-N-11-O-oxazine derivative which is formed by condensation of 9(S)-erythromycylamine with 2-(2-methoxyethoxy)acetaldehyde. Dirithromycin is hydrolyzed, either under acidic conditions or in vivo, to its major active metabolite, 9(S)-erythromycylamine. The antimicrobial spectrum of dirithromycin is similar to that of erythromycin; both(More)
A series of 20-deoxo-20-cyclic (alkylamino) derivatives of tylosin, desmycosin, macrocin and lactenocin was prepared by reductive amination of the C-20 aldehyde group. The majority of the compounds were prepared using metal hydrides (sodium cyanoborohydride or sodium borohydride) as the reducing agents and a suitable cyclic alkylamine. Subsequently, a more(More)
A54145 complex is made up of eight factors; A, A1, B, B1, C, D, E, and F which were active in vitro (MIC 0.25 approximately greater than 32 micrograms/ml) against Gram-positive aerobic organisms. The complex, factor B and B1 were found to be active against two strains of Clostridium perfringens. A calcium dependence study on some of the factors showed that(More)
Modification of the aldehyde group in tylosin and related macrolide antibiotics dramatically enhanced the oral efficacy of the derivatives against experimental infections caused by susceptible bacteria in laboratory animals. A large number and wide variety of aldehyde-modified macrolide derivatives were prepared, utilizing the Mitsunobu reaction and other(More)
Three positional analogues (4-, 5-, and 7-) of benzothienylglycine and (N-acetylindolinyl)-5-glycine were prepared and coupled to 7-aminodeacetoxycephalosporanic acid (7-ADCA) to give the cephalosporins 17a-c. In addition two isomeric (2,3-b and 3,2-b) thienothiopheneglycines were synthesized and coupled to 7-ADCA to yield cephalosporins 30d and 30e. In(More)
Over eighty N-alkyl vancomycins were synthesized by reductive alkylation of vancomycin with the appropriate aldehydes. The N-alkyl vancomycins exhibit greater antibacterial activity than the corresponding N-acyl vancomycins and the parent antibiotic. Some of these semisynthetic vancomycins are five times more active than vancomycin. The N-alkyl vancomycins(More)