Synthesis and antibacterial activity of 6-O-arylpropargyl-9-oxime-11,12-carbamate ketolides

A series of novel 6-O-arylpropargyl-9-oxime-ketolides was synthesized and evaluated against various pathogens. These new compounds show promising in vitro antibacterial potency and in vivo efficacy against macrolide resistant strains.     

Synthesis and antibacterial activity of 6-O-(heteroaryl-isoxazolyl)propynyl 2-fluoro ketolides

Macrolide antibiotics are widely prescribed for the treatment of respiratory tract infections; however, the increasing prevalence of macrolide-resistant pathogens is a public health concern. Therefore, the development of new macrolide derivatives with activities against resistant pathogens is urgently needed. A series of novel 6-O-(heteroaryl-isoxazolyl)propynyl 2-fluoro ketolides has been synthesized from erythromycin A. These compounds have shown very promising in vitro and in vivo antibacterial activities against key respiratory pathogens including erythromycin-susceptible/resistant strains.     

Synthesis and antibacterial activity of C6-carbazate ketolides

A novel series of ketolides containing heteroaryl groups that are linked to the erythronolide ring via a C6-carbazate functionality has been successfully synthesized. Careful modulation of the heteroaryl groups, the length and degree of saturation of the C6-carbazate linker, and the substituents present on each of the carbazate nitrogens led to compounds with potent activity against key bacterial respiratory pathogens. The best analogs of this series had in vitro and in vivo (sc dosing) profiles that were comparable to telithromycin.     

Synthesis and antibacterial activity of new 9-O-arylpropenyloxime ketolides

A novel series of 9-O-arylpropenyloxime ketolide was synthesized and evaluated for their antibacterial activity. This series of ketolide exhibited potent activity against clinically isolated gram-positive strains including Staphylococcus pneumoniae and Straptococcus Pyogenes.     

Synthesis and antibacterial activity of C12 des-methyl ketolides

Synthesis of C(12) des-methyl ketolide is developed featuring an intramolecular epoxide formation/elimination process to establish the C(12) stereocenter. These ketolides are potent against several key respiratory pathogens, including erythromycin resistant erm- and mef-containing strains of Streptococcus pneumoniae.     

Synthesis and antibacterial activity of novel C12 ethyl ketolides

A novel series of C(12) ethyl erythromycin derivatives have been discovered which exhibit in vitro and in vivo potency against key respiratory pathogens, including those resistant to erythromycin. The C(12) modification involves replacing the natural C(12) methyl group in the erythromycin core with an ethyl group via chemical synthesis. From the C(12) ethyl macrolide core, a series of C(12) ethyl ketolides were prepared and tested for antibacterial activity against a panel of relevant clinical isolates. Several compounds were found to be potent against macrolide-sensitive and -resistant bacteria, whether resistance was due to ribosome methylation (erm) or efflux (mef). In particular, the C(12) ethyl ketolides 4k,4s,4q,4m, and 4t showed a similar antimicrobial spectrum and comparable activity to the commercial ketolide telithromycin. The in vivo efficacy of several C(12) ethyl ketolides was demonstrated in a mouse infection model with Streptococcus pneumoniae as pathogen.     

Beta-keto-ester chemistry and ketolides. Synthesis and antibacterial activity of 2-halogeno, 2-methyl and 2,3 enol-ether ketolides

The effect of 2,3 modifications on the antibacterial activity of ketolides was evaluated by introducing substituents in position 2 and converting the C-1, C-2, C-3 beta-keto-ester into stable 2,3 enol-ether or 2,3 anhydro derivatives. Introduction of a fluorine in C-2 is beneficial with regard to the overall antibacterial spectrum whereas the enol-ether and 2,3 unsaturated compounds, as well as the bulky gem dimethyl or 2-chloro derivatives, are less active particularly against erythromycin resistant strains. A 2-fluoro ketolide derivative demonstrates good antibacterial activity and in vivo efficacy against multi-resistant Streptococcus pneumoniae. Compared to azithromycin against Haemophilus influenzae, this compound is equivalent in vitro and slightly more active in vivo. These results demonstrate that within the ketolide class, to retain good antibacterial activity, position 2 needs to remain tetrahedral and tolerates only very small substituents such as fluorine.     

Synthesis and antibacterial activity of C11, C12-cyclic urea analogues of ketolides

C11, C12-cyclic urea analogues of ketolides were designed and synthesized by use of a novel ketene acetal intermediate. This intermediate enabled introduction of an amino group at C12 stereospecifically and in high yield. The resulting cyclic urea ketolides appear to have in vitro activity similar to that of telithromycin which contains a C11, C12 cyclic carbamate moiety. Some of the C2 fluorinated compounds have improved potency against erm-containing Streptococcus pyogenes.     

Synthesis and antibacterial activity of novel modified 5-O-desosamine ketolides

A series of novel modified 5-O-desosamine-ketolides were synthesized. The 5-O-desosamine fragment was removed from ketolide by an efficient and mild manipulation. 4-O-substituted desosamine was introduced into the ketolide aglycon and various coupling methods were essayed for the glycosylation. Three novel ketolides were tested for in vitro antibacterial activity against a panel of susceptible and resistant pathogens. Compound 26 showed potent activity against all the methicillin-sensitivity and resistant pathogens.     

Synthesis of 9-oxime-11,12-carbamate ketolides through a novel N-deamination reaction of 11,12-hydrazonocarbamate ketolide

A series of 9-oxime-11,12-carbamate ketolides was synthesized for the first time through a key 11,12-hydrazonocarbamate intermediate that was first oximated and further deaminated to give the corresponding carbamate. The N-N bond cleavage was achieved through an original new reaction using glycoaldehyde dimer as deaminating reagent. The new compounds synthesized were shown to display improved antibacterial activities against Streptococcus pneumoniae and S. pyogenes resistant to erythromycin.     

Synthesis and antibacterial activity of C-6 carbamate ketolides, a novel series of orally active ketolide antibiotics

A new series of antibacterial ketolides is reported, which features the use of a C-6 carbamate for tethering the arylalkyl sidechain to the macrolide core. The best members of this series display in vitro and in vivo activity comparable to telithromycin. Partial epimerization at C-2, unobserved in previously reported ketolides, was noted for this series.     

Synthesis and antibacterial activity of novel ketolides with 11,12-quinoylalkyl side chains

A series of quinoylalkyl side chains was designed and synthesized, followed by introduction into ketolides by coupling with building block 6 or 32. The corresponding targets 7a–n, 33b, and 33e were tested for their in vitro activities against a series of macrolide-sensitive and macrolide-resistant pathogens. Some of them showed a similar antibacterial spectrum and comparable activity to telithromycin. Among them, two C2-F ketolides, compounds 33b and 33e, displayed excellent activities against macrolide-sensitive and macrolide-resistant pathogens.     

Synthesis and antibacterial evaluation of novel 11-O-carbamoyl clarithromycin ketolides

A series of novel 11-O-carbamoyl clarithromycin ketolides were designed, synthesized and evaluated for their in vitro antibacterial activity. The results showed that the majority of the target compounds displayed improved activity compared with references against erythromycin-resistant S. pneumoniae A22072 expressing the mef gene, S. pneumoniae B1 expressing the erm gene and S. pneumoniae AB11 expressing the mef and erm genes. In particular, compounds 9, 18, 19 and 22 showed the most potent activity against erythromycin-resistant S. pneumoniae A22072 with the MIC values of 0.5 μg/mL. Furthermore, compounds 11, 18, 19, 24 and 29 were also found to exhibit favorable antibacterial activity against erythromycin-susceptible S. pyogenes with the MIC values of 0.125–1 μg/mL, and moderate activity against erythromycin-susceptible S. aureus ATCC25923 and B. subtilis ATCC9372.     

Synthesis and antibacterial activity of 9-substituted minocycline derivatives

A number of 9-acylamino and 9-sulfonylamino derivatives of minocycline have been synthesized for structure-activity relationship studies. These compounds showed activity against both tetracycline-susceptible and tetracycline-resistant strains. Many of the 9-sulfonylamino derivatives exhibited improved antibacterial activity against a number of tetracycline- and minocycline-resistant Gram-positive pathogens.     

Synthesis and antibacterial activity of 6-O-heteroarylcarbamoyl-11,12-lactoketolides

A new series of erythromycin A derivatives, the 6-O-heteroarylcarbamoyl-11,12-lactoketolides, with activity against macrolide-resistant streptococci, are described. Structurally, these macrolide antibiotics are characterized by a heteroaryl side chain attached to the macrolactone core through a carbamate linkage at the C6 position, as well as 11,12-gamma-lactone and 3-keto functionalities. The synthesis and antibacterial activity of this new series of ketolides are discussed.     

Synthesis and evaluation of N-alkyl-9-aminoacridines with antibacterial activity

A series of 9-alkylaminoacridines were synthesized and evaluated for activity against two strains of methicillin-resistant and one strain of methicillin-sensitive Staphylococcus aureus. Results are presented that show a clear structure activity relationship between the N-alkyl chain length and antibacterial activity with peak MIC₉₉ values of 2–3 μM for alkyl chains ranging from 10 to 14 carbons in length. Although prior work has linked the function of acridine-based compounds to intercalation and topoisomerase inhibition, the present results show that 9-alkylaminoacridines likely function as amphiphilic membrane-active disruptors potentially in a similar manner as quaternary ammonium antimicrobials.     

Synthesis,characterization and biological activity of ring-substituted 6-benzylamino-9-tetrahydropyran-2-yl and 9-tetrahydrofuran-2-ylpurine derivatives

In an attempt to improve specific biological functions of cytokinins routinely used in plant micropropagation, 33 6-benzylamino-9-tetrahydropyran-2-ylpurine (THPP) and 9-tetrahydrofuran-2-ylpurine (THFP) derivatives, with variously positioned hydroxy and methoxy functional groups on the benzyl ring, were prepared. The new derivatives were prepared by condensation of 6-chloropurine with 3,4-dihydro-2H-pyran or 2,3-dihydrofuran and then by the condensation of these intermediates with the corresponding benzylamines. The prepared compounds were characterized by elemental analyses, TLC, HPLC, melting point determinations, CI+ MS and ¹H NMR spectroscopy. The cytokinin activity of all the prepared derivatives was assessed in three classical cytokinin bioassays (tobacco callus, wheat leaf senescence and Amaranthus bioassay). The derivatives 6-(3-hydroxybenzylamino)-9-tetrahydropyran-2-ylpurine (3) and 6-(3-hydroxybenzylamino)-9-tetrahydrofuran-2-ylpurine (23) were selected, because of the high affinity of their parent compound meta-topolin (mT, 6-(3-hydroxybenzylamino)purine) to cytokinin receptors, as model compounds for studying their perception by the receptors CRE1/AHK4 and AHK3 in a bacterial assay. Both receptors perceived these two derivatives less well than they perceived the parent compound. Subsequently, the susceptibility of several new derivatives to enzyme degradation by cytokinin oxidase/dehydrogenase was studied. Substitution of tetrahydropyran-2-yl (THP) at the N⁹ position decreased the turnover rates of all new derivatives to some extent. To provide a practical perspective, the cytotoxicity of the prepared compounds against human diploid fibroblasts (BJ) and the human cancer cell lines K-562 and MCF-7 was also assayed in vitro. The prepared compounds showed none or marginal cytotoxicity compared to the corresponding N⁹-ribosides. Finally, the pH stability of the two model compounds was assessed in acidic and neutral water solutions (pH 3–7) by high-performance liquid chromatography (HPLC).     

Synthesis and antibacterial activity of derivatives of 6-O-allylic acylides

A series of novel acylide derivatives have been synthesized from erythromycin A via a facile procedure. By applying this procedure, cyclic carbonation to C-11,12 position, acylation to C-3 hydroxyl, and deprotection provided the desired acylides. These compounds showed antibacterial activity against both macrolide-susceptible strains and macrolide-resistant strains. Because of existence of 6-O-allyl substitution, these derivatives can be used as intermediates for further structural modification.     

Synthesis and antibacterial activity of novel 6-O-substituted erythromycin A derivatives

A series of novel 6-O-substituted erythromycin A derivatives has been synthesized. Good in vitro antibacterial activity has been demonstrated for analogues incorporating a variety of structural features. The methodology disclosed is expected to find application in the design of future macrolide antibiotics that target the prevalent bacterial resistance problem.     

Synthesis and biological activity of 2-fluoro adenine and 6-methyl purine nucleoside analogs as prodrugs for suicide gene therapy of cancer

A novel series of 6-methylpurine nucleoside derivatives with substitutions at 5-position have been synthesised These compounds bear a 5'-heterocycle such as triazole or a imidazole with a two carbon chain, and an ether, thio ether or amine. To extend the SAR study of 2-fluoroadenine and 6-methyl purine nucleosides, their corresponding alpha-linker nucleosides with L-xylose and L-lyxose were also synthesized. All of these compounds have been evaluated for their substrate activity with E. coli PNP.