Novel azalides derived from sixteen-membered macrolides

Synthesis and antibacterial activity of novel lincomycin derivatives. IV. Optimization of an N-6 substituent

The design and synthesis of lincomycin derivatives modified at the C-6 and C-7 positions are described. A substituent at the C-7 position is a 5-aryl-1,3,4-thiadiazol-2-yl-thio group that generates antibacterial activities against macrolide-resistant Streptococcus pneumoniae and Streptococcus pyogenes carrying an erm gene. An additional modification at the C-6 position was explored in application of information regarding pirlimycin and other related compounds. These dual modifications were accomplished by using methyl α-thiolincosaminide as a starting material. As a result of these dual modifications, the antibacterial activities were improved compared with those of compounds with a single modification at the C-7 position. The antibacterial activities of selected compounds in this report against macrolide-resistant S. pneumoniae and S. pyogenes with an erm gene were superior to those of telithromycin.

Synthesis and structure-activity relationships of novel lincomycin derivatives part 3: discovery of the 4-(pyrimidin-5-yl)phenyl group in synthesis of 7(S)-thiolincomycin analogs

Novel lincomycin derivatives possessing an aryl phenyl group or a heteroaryl phenyl group at the C-7 position via sulfur atom were synthesized by Pd-catalyzed cross-coupling reactions of 7(S)-7-deoxy-7-thiolincomycin (5) with various aryl halides. This reaction is the most useful method to synthesize a variety of 7(S)-7-deoxy-7-thiolincomycin derivatives. On the basis of analysis of structure-activity relationships of these novel lincomycin derivatives, we found that (a) the location of basicity in the C-7 side chain was an important factor to enhance antibacterial activities, and (b) compounds 22, 36, 42, 43 and 44 had potent antibacterial activities against a variety of Streptococcus pneumoniae with erm gene, which cause severe respiratory infections, even compared with our C-7-modified lincomycin analogs (1-4) reported previously. Furthermore, 7(S)-configuration was found to be necessary for enhancing antibacterial activities from comparison of configurations at the 7-position of 36 (S-configuration) and 41 (R-configuration).

Synthesis, Antibacterial, and Anticancer Evaluation of Novel Spiramycin-Like Conjugates Containing C(5) Triazole Arm

Huisgen cycloaddition allowed obtaining of novel triazole-bridged antibiotics (6-16) with the reconstructed C(5) arm of spiramycin. (1)H-(1)H NOESY couplings indicated the structure of novel derivatives in solution and demonstrated that the rebuilt C(5) arm is slightly differently oriented relative to the aglycone part if compared to that of spiramycin (1). Combined analysis of biological data together with experimentally determined lipophilicity (clogP) and solubility show the importance of the chemical nature of the newly introduced triazole C(5) arm in the presence of attractive antibacterial and anticancer potency. The most cytotoxic active triazole conjugates having a hydrophobic and bulky C(5) arm showed higher selectivity toward cancer cell lines (HeLa, KB, MCF-7, Hep-G2, and U87) relative to HDF normal cells than that of the parent spiramycin. Our studies have demonstrated that the aldehyde group is not crucial for the presence of interesting antibacterial [MIC(S. pneumoniae) ∼ 1.2 μM] and anticancer [IC50(HepG2) ∼ 6 μM] properties of 16-membered lactone macrolides based on spiramycin's aglycone.

Synthesis of 17-membered azalides from a 16-membered macrolide utilizing amide-selective silane reduction

Novel 17-membered azalides of N-methylated amine type were synthesized and their antibacterial activity was evaluated.

Update on carbohydrate-containing antibacterial agents

BACKGROUND

Since the first known use of antibiotics > 2,500 years ago, a research field with immense importance for the welfare of mankind has been developed. After a decrease in interest in this topic by the end of the 20th century the occurrence of (poly-)resistant strains of bacteria induced a revival of antibiotics research. Health systems have been seeking viable and reliable solutions to this dangerous and expansive threat.

OBJECTIVE

This review will focus on carbohydrate-containing antibiotics and will give an outline of recently published novel isolated, semisynthetic as well as synthetic structures, their mechanism of action, if known, and the strategies for the design of compounds with potential by improved antibacterial properties.

METHODS

The literature between 2000 and 2008 was screened with main focus on recent examples of novel structures and strategies for the lead finding of exclusively antibacterial agents.

RESULTS/CONCLUSION

With the explanation of the role of the carbohydrate moieties in the respective antibacterial agents together with better synthetic strategies in carbohydrate chemistry as well as improvements in assay development for high throughput screening methods, carbohydrate-containing antibiotics can be used for the finding of potential drug leads that contribute to the fight against infections and diseases caused by (resistant) bacterial pathogens.

New macrolide, lincosaminide and streptogramin B antibiotics

IMPORTANCE OF THE FIELD

New antibiotics are needed to overcome microbial resistance and to improve on the therapeutic index and clinical effectiveness of existing agents.

AREA COVERED IN THIS REVIEW

This review covers the journal and patent literature published from about the mid-2000s to 2010 to provide an overview of the large diversity of new chemical entities in the macrolide, lincosaminide and streptogramin B (MLS(B)) class.

WHAT THE READER WILL GAIN

The review identifies areas of the greatest effort and recent results in pursuing structure-activity relationships among MLS(B) antibiotics and highlights preclinical and clinical candidates that have arisen from these diverse discovery programs.

TAKE HOME MESSAGE

Research on the MLS(B) class appears promising for the eventual registration and commercialization of several new antibiotics that improve the clinical effectiveness of existing agents and combat antibiotic-resistant pathogens.

Structure elucidation, complete NMR assignment and PM5 theoretical studies of new hydroxy-aminoalkyl-alpha,beta-unsaturated derivatives of the macrolide antibiotic josamycin

Four new hydroxy-aminoalkyl derivatives of alpha,beta-unsaturated macrolide-josamycin (2-5) have been synthesised and their structures have been studied by means of (1)H and (13)C NMR and FT-IR methods. Complete assignment of resonances in the (1)H and (13)C NMR spectra has been made on the basis of (1)H-(13)C HSQC, (1)H-(13)C HMBC, (1)H-(1)H COSY, (1)H-(1)H NOESY 2D experiments. Spectroscopic data indicated that for the derivatives 3 and 4 some equilibrium between two different structures exists in contrast to derivatives 2 and 5. The lowest-energy structures of the new derivatives of josamycin have been calculated and visualised by PM5 method at semi-empirical level of theory, taking into account the NMR and FT-IR data. The most significant differences between the structures of josamycin and its newly synthesised derivatives' were found in the conformation of the macrolide aglycone part and in the mutual orientation of the 4-O-isovalerylmycarosylmycaminose moiety relative to the aglycone part. PM5 semi-empirical calculations indicated that the structures of the new macrolide derivatives are stabilised by rather weak intramolecular hydrogen bonds in agreement with spectroscopic data. Antimicrobial properties of the new derivatives 2-5 as well as those having an acetate group at C-3 (6 and 7) were determined and compared to that of the parent macrolide antibiotic josamycin (1).

Novel azalides derived from 16-membered macrolides. III. Azalides modified at the C-15 and 4'' positions: Improved antibacterial activities

The design and synthesis of 16-membered azalides modified at the C-15 and 4'' positions are described. The compounds we report here are characterized by an arylpropenyl group attached to the C-15 position of macrolactone and a carbamoyl group at the C-4'' position in a neutral sugar. Introduction of alkylcarbamoyl groups to the C-4'' position was regioselectively achieved by unique and convenient methods via acyl migration. As a result of optimization at the C-3 and 15 positions, several compounds were found to have potent activity against mef- and erm-resistant bacterial strains. These results suggest that 16-membered azalides could be promising compounds as clinical candidates.

Novel ureas and thioureas of 15-membered azalides with antibacterial activity against key respiratory pathogens

The new ureas and thioureas of 15-membered azalides, N''-substituted 9a-(N'-carbamoyl-gamma-aminopropyl) (4), 9a-(N'-thiocarbamoyl-gamma-aminopropyl) (6), 9a-[N'-(beta-cyanoethyl)-N'-(carbamoyl-gamma-aminopropyl)] (8) and 9a-[N'-(beta-cyanoethyl)-N'-(thiocarbamoyl-gamma-aminopropyl)] (10) of 9-deoxo-9-dihydro-9a-aza-9a-homoerythromycin A (2), were synthesized and structurally characterized by NMR and IR spectroscopic methods and mass spectrometry. The new compounds were evaluated in vitro against a panel of erythromycin susceptible and erythromycin-resistant gram-positive and gram-negative bacterial strains. These compounds displayed an excellent overall antibacterial in vitro activity against erythromycin sensitive gram-positive strains, Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, and good against negative strains, Moraxella catarrhalis and Haemophilus influenzae. In addition, several ureas with naphthyl substituents (4f, 4g, 4h) showed better activity in comparison to azithromycin against inducible resistant S. pyogenes. Ureas with naphthyl substituents 4g, 4h and thiourea 8h displayed moderate activity against constitutively resistant S. pneumoniae.