[Comprehensive synthetic study of muraymycins toward the development of novel antibacterial agents].

This review describes the synthesis and structure-activity relationship (SAR) study of muraymycins (MRYs), which are potent antibacterial nucleoside antibiotics. The key elements of our synthetic approach include the preparation of L-epi-capreomycidine via a C-H amination reaction and a convergent assemblage to construct of the framework of MRYs using Ugi four component reaction. With this approach the first total synthesis of MRY D2 and its epimer, epi-MRY D2, which does not have lipophilic substituents, has been accomplished. The fact that MRY D2 and it's epimer did not show any antibacterial activity indicated the lipophilic substituents of MRYs plays an important role in membrane-permeability. Hence, MRY analogues with lipophilic substituents were designed and synthesized simply by altering the aldehyde component in Ugi four-component assemblage. The MRY analogues with lipophilic substituents exhibited improved antibacterial activity against anti drug-resistant bacteria. It was also suggested that the accessory urea-dipeptide motif might contribute to MraY inhibitory and antibacterial activity. Our synthetic approach would effectively provide a variety of MRY analogues and resultant SAR information brings us directions to create further MRY analogues.

A novel series of parenteral cephalosporins exhibiting potent activities against both Pseudomonas aeruginosa and other gram-negative pathogens. Part 2: Synthesis and structure-activity relationships.

A novel series of 7beta-[2-(2-amino-5-chloro-thiazol-4-yl)-2(Z)-((S)-1-carboxyethoxyimino)acetamido]cephalosporins bearing various pyridinium groups at the C-3' position were synthesized and their in vitro antibacterial activities against gram-negative pathogens including Pseudomonas aeruginosa and several gram-positive pathogens were evaluated. Among the cephalosporins prepared, we found that a cephalosporin bearing the 2-amino-1-(3-methylamino-propyl)-1H-imidazo[4,5-b]pyridinium group at the C-3' position (8a) showed potent and well-balanced antibacterial activities against P. aeruginosa and other gram-negative pathogens including the strains which produce class C beta-lactamase and extended spectrum beta-lactamase (ESBL). Compound 8a also showed efficacious in vivo activity and high stability against AmpC beta-lactamase. These findings indicate that 2-aminoimidazopyridinium having an aminoalkyl group at the 1-position as a C-3' side chain is suitable for cephalosporins bearing an aminochlorothiazolyl moiety and a carboxyethoxyimino moiety on the C-7 side chain.

A novel series of parenteral cephalosporins exhibiting potent activities against Pseudomonas aeruginosa and other Gram-negative pathogens: synthesis and structure-activity relationships.

A series of 7beta-[2-(2-aminothiazol-4-yl)-2-(Z)-(carboxymethoxyimino)acetamido]cephalosporins bearing a 1-(substituted)-1H-pyrrolo[3,2-b]pyridinium group at C-3' position was synthesized and their in vitro antibacterial activities against Pseudomonas aeruginosa and other Gram-negative pathogens were evaluated. Among the cephalosporins prepared, 7beta-[2-(2-amino-5-chlorothiazol-4yl)-2(Z)-((S)-1-carboxyethoxyimino)acetamido]cephalosporins (42d) showed potent antibacterial activities against P. aeruginosa and other Gram-negative pathogens including the strains which produce class C beta-lactamase and extended spectrum beta-lactamase (ESBL). These results imply that both the Cl atom on the C-7 aminothiazole moiety and the alpha-substituent at the iminoether moiety are essential for the stability against beta-lactamase and the potent activity against Gram-negative bacteria including P. aeruginosa.

A new type of ketolide bearing an N-aryl-alkyl acetamide moiety at the C-9 iminoether: synthesis and structure-activity relationships.

A new type of ketolide bearing an N-aryl-alkyl acetamide moiety at the C-9 iminoether and its analogues were prepared, and their antibacterial activities and pharmacokinetic properties were evaluated. We found that the introduction of an (R)-alkyl group between the amide and iminoether groups could improve the pharmacokinetic properties while maintaining the activity against erythromycin-resistant Streptococcus pneumoniae. Among the ketolides prepared with the (R)-alkyl group, compound 5p with an N-(3-quinoxalin-6-yl-propyl)-propionamide moiety was found to have in vivo efficacy comparable to CAM with potent in vitro antibacterial activities against the key respiratory pathogens including Haemophilus influenzae and erythromycin-resistant S. pneumoniae.

A new type of ketolides bearing an N-aryl-alkyl acetamide moiety at the C-9 iminoether synthesis and structure-activity relationships.

A new type of ketolides, bearing an N-aryl-alkyl acetamide moiety at the C-9 iminoether and a cyclic carbonate at the C-11,12 position was prepared and the antibacterial activities of the compounds were evaluated. Some of the derivatives showed potent antibacterial activity against both Haemophilus influenzae and Streptococcus pneumoniae, which are clinically important respiratory tract pathogens. Among the derivatives prepared, compound 5s with a quinolin-4-yl moiety was found to have potent and well-balanced activity against S. pneumoniae and H. influenzae including erythromycin-resistant strains.

A simple method for deprotection of the N- and O-carbobenzoxy groups and N-methylation of the desosamine sugar moiety of ketolides. Application to the synthesis of ketolide analogues with various 9-iminoether moieties and their antibacterial activities.

A simple synthetic method for deprotection of the N- and O-carbobenzoxy groups (Cbz) of the desosamine sugar moiety of ketolides is reported. This deprotection method is applicable to the synthesis of a variety of ketolide analogues with various 9-iminoether moieties in good to moderate yield. Among the ketolide derivatives prepared by this method, compound 7g with a quinoline-6-yl moiety showed potent activity against erythromycin-resistant pathogens as well as Haemophilus influenzae.