Studies on cephalosporin antibiotics. V. Synthesis, antibacterial activity and oral absorption of new 3-[(Z)-2-methoxycarbonylvinylthio]-7 beta- [(Z)-2-(2-aminothiazol-4-yl)-2-(oxyimino)acetamido]cephalosporins.

A series of new 3-[(Z)-2-methoxycarbonylvinylthio]-7 beta-[(2- aminothiazol-4-yl)acetamido]-cephalosporins (1) having various oxyimino groups (Z-form) at the alpha position of the C-7 side chain was synthesized and evaluated for antibacterial activity and oral absorption in rats. Of these, the cephalosporin (1a) with a hydroxyimino group in the C-7 side chain showed a potent antibacterial activity against Gram-negative bacteria and Gram-positive Staphylococcus aureus as well as good oral absorption in rats. The structure-activity relationships of 1 are also presented.     

Studies on cephalosporin antibiotics. II. Synthesis, antibacterial activity and oral absorption of 3-alkoxycarbonylmethoxy-7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(O-substituted oxyimino)-acetamido]cephalosporins

The synthesis, antibacterial activity and oral absorption in rats of 3-alkoxycarbonyl-methoxy-7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(O-substituted oxyimino)acetamido]cephalosporins (1) are described. In this cephalosporin series, 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(carboxy-methoxyimino)acetamid o] cephalosporins (1b, 1i and 1j) with a lower alkoxycarbonylmethoxy group at the C-3 position of a cephem nucleus exhibited not only potent activity against Gram-negative bacteria but also good oral absorption in rats. Structure-activity relationships of 1 are also presented.     

Studies on cephalosporin antibiotics. IV. Synthesis, antibacterial activity and oral absorption of new 3-(2-substituted-vinylthio)-7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2- (carboxymethoxyimino)acetamido]cephalosporins.

A series of new 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(carboxymethoxyimino)ace tamido] cephalosporins (1) having various substituted-vinylthio groups at the C-3 position of the cephen nucleus was synthesized and evaluated for antibacterial activity and oral absorption in rats in comparison with cefixime. Of these, the cephalosporins (1a and 1c) with a lower alkoxycarbonylvinylthio group (Z-form) at the C-3 position showed a potent antibacterial activity against Gram-negative bacteria, improved activity against Staphylococcus aureus as well as good oral absorption in rats. The structure-activity relationships of 1 are also presented.     

Studies on cephalosporin antibiotics. III. Synthesis, antibacterial activity and oral absorption of new 3-(substituted-alkylthio)-7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2- (carboxymethoxyimino)acetamido]cephalosporins

The synthesis, antibacterial activity and oral absorption in rats of new 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(carboxymethoxyimino)ace tamido] cephalosporins (1) having various substituted-alkylthio groups at the C-3 position of the cephem nucleus are described. Of these, the cephalosporins with a cyanomethylthio group (1d) and fluoroethylthio group (1p) at the C-3 position showed a potent in vitro antibacterial activity against Gram-positive and Gram-negative bacteria as well as good oral absorption in rats. When administered orally to mice infected with Klebsiella pneumoniae, 1d had stronger protective effect than 1p. The structure-activity relationships of 1 are also presented.     

Improved synthesis of an ester-type prodrug, 1-acetoxyethyl 7-[(Z)-2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]-3-[(Z)-1- propenyl]-3-cephem-4-carboxylate (BMY-28271)

1-Acetoxyethyl 7-[(Z)-2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]-3- [(Z)-1-propenyl]-3-cephem-4-carboxylate (BMY-28271) is an ester-type prodrug of cephalosporin for oral use. Methods suitable for large scale preparation were investigated. The yield was improved by esterification of 7-[(Z)-2-(2-aminothiazol-4-yl)-2-trityloxyiminoacetamido]cep hem-4-carboxylic acid (11) followed by removal of the trityl group and, in addition, column chromatographic purification at each step was eliminated by optimization of the reaction conditions.     

Studies on cephalosporin antibiotics. VI. Synthesis, antibacterial activity and oral efficacy in mice of new 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(hydroxyimino)-acetamido]-3- (substituted alkylthio)cephalosporins.

A series of new 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(hydroxyimino)acetamido] cephalosporins (1) having various substituted alkylthio groups at the C-3 position of the cephem nucleus were prepared and evaluated for antibacterial activity and oral absorption in rats. Of these, the cephalosporin with a cyanomethylthio group (1a) showed the greatest activity against Staphylococcus aureus and Gram-negative bacteria. Its pivaloyloxymethyl ester (6a), a representative prodrug, exhibited good in vivo efficacy in mice by oral administration. The structure-activity relationships of 1 are also presented.     

Studies on FK482 (Cefdinir). III. Synthesis and structure-activity relationships of 7 beta-[(Z)-2-aryl-2-hydroxyiminoacetamido]-3-vinyl-3- cephem-4-carboxylic acid derivatives

The synthesis, antibacterial activity and oral absorption of the 7 beta-[(Z)-2-aryl-2-hydroxyiminoacetamido]-3-vinylcephalosporins (Ia--e) are described. All of these compounds exhibited excellent activity against Staphylococcus aureus. Against Gram-negative bacteria FK482 exhibited more excellent activity than the other compounds (Ia--e). These compounds except Ie showed good oral absorption. The relationship between the oral absorption rates and the lipophilicity of these cephalosporins is discussed.     

Studies on beta-lactam antibiotics. XIX. Structure-activity relationships of cephalosporins having a thiadiazolylthiomethyl group at the C-3 side chain

The synthesis and antibacterial activity of 7 beta-[(Z)-2-(2-amino-4-thiazolyl)-2-(hydroxy or alkoxy)iminoacetamido]cephalosporins with various thiadiazolylthiomethyl moieties at the 3-position are discussed. Of the compounds (1a-1e, 7a-7d), 7 beta-[(Z)-2-(2-amino-4-thiazolyl)-2-hydroxyiminoacetamido]-3-[(1,2 ,4- thiadiazol-5-yl)thiomethyl]cephalosporin (1d: FK312) exhibited the highest activity against Gram-positive and Gram-negative bacteria, especially, against methicillin-resistant Staphylococcus aureus. Furthermore, the pharmacokinetic profiles of the compound 1d showed longer serum levels than that of ceftriaxone in rats.     

Synthesis and structure-activity relationships of 7 beta-[2-(2-aminothiazol-4-yl)acetamido]cephalosporin derivatives. V. Synthesis and antibacterial activity of 7 beta-[2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]-cephalosporin derivates and related compounds

In order to improve the antibacterial activity of 7 beta-[2-(2-aminothiazol-4-yl)acetamido]-cephalosporins new derivatives having a methoxyimino moiety in the 7-acyl side chain and related compounds were synthesized. Of these, 7 beta-[2-(2-aminothiazol-4-yl)-(Z)-2-methoxyiminoacetamido]-cephalosporins were found to possess excellent activity against a variety of Gram-positive and Gram-negative bacteria including beta-lactamase-producing strains. An extensive study of structure-activity relationships led to the selection of 7 beta-[2-(2-aminothiazol-4-yl)-(Z)-2-methoxyiminoacetamido]-3-[(1-methyl-1H-tetrazol-5-yl) thiomethyl]-ceph-3-em-4-carboxylic acid, SCE-1365, for further biological and clinical evaluation.     

Studies on condensed-heterocyclic azolium cephalosporins. IV. Synthesis and antibacterial activity of 7 beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)- alkoxyiminoacetamido]-3-(condensed-heterocyclic azolium)methyl cephalosporins including SCE-2787.

The synthesis and in vitro antibacterial activity of 7 beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-alkoxyiminoacetami do] cephalosporins bearing various condensed-heterocyclic azolium groups at the 3 position in the cephalosporin nucleus are described. The thiadiazolyl cephalosporins showed good antibacterial activity against both Gram-positive and Gram-negative bacteria and the MICs of the thiadiazolyl cephalosporins against Pseudomonas aeruginosa was more potent than that of the corresponding 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-alkoxyiminoacetamido]-3- (condensed-heterocyclic azolium)methyl cephalosporins. Also, the thiadiazolyl cephalosporins bearing (imidazo[1,2-b]-pyridazinium-1-yl)methyl groups at the 3 position showed antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Among the cephalosporins tested, 7 beta-[2-(5- amino-1,2,4-thiadiazol-3-yl)-2(Z)-methoxyiminoacetamido]-3-(imidaz o[1,2- b]pyridazinium-1-yl)methyl-3- cephem-4-carboxylate (4, SCE-2787) which exhibited the most potent antibacterial activity and the broadest antibacterial spectrum was selected as a parenteral cephalosporin candidate for further biological evaluation.     

Studies on anti-MRSA parenteral cephalosporins. III. Synthesis and antibacterial activity of 7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-alkoxyiminoacetamido-3

In the course of our exploration for a novel cephalosporin derivative having excellent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), we modified the C-3 linked spacers of cephem derivatives bearing a 1-methylimidazo[1,2-b]pyridazinium-6-yl group at the C-3' position and 2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-cyclopentyloxy-iminoacetyl group at the C-7 position. The optimal spacers were the (E)-2-vinyl and (E)-2-thiovinyl groups seen in 19a and 29aa, respectively. Their anti-MRSA activity was 16 to 32 times as potent as that of cefozopran (CZOP). Focusing on the (E)-2-vinyl and (E)-2-thiovinyl spacers, we further modified the alkoxyimino groups in the C-7 acyl moiety and the 1-alkylimidazo[1,2-b]pyridazinium moieties at the C-3' position and investigated the structure-activity relationships (SAR) of the derivatives. Consequently, we selected 7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-fluoromethoxyiminoacetamido]-3-[(E)-2-(1-methylimidazo[1,2-b]pyridazinium-6-yl)thiovinyl]-3-cephem-4-carboxylate (29ca) as a new anti-MRSA parenteral cephalosporin candidate for further biological evaluation. The selected 29ca showed anti-MRSA activity comparable to that of vancomycin (VCM) both in vitro and in vivo, high affinity (IC50)=2.7 microg/ml) for penicillin binding protein 2' (PBP2') of MRSA and potent activity against Gram-negative bacteria as well.     

Studies on condensed-heterocyclic azolium cephalosporins. III. Synthesis and antibacterial activity of 7 beta-[2-(2-amino-5-substituted-thiazol-4-yl)-2 (Z)-alkoxyiminoacetamido]-3-(condensed-heterocyclic azolium)methyl-3-cephem-4- carboxylates.

As a part of our research on the synthesis of cephalosporins bearing condensed-heterocyclic azolium groups at the 3 position in the cephalosporin nucleus, we describe herein the synthesis of 7 beta-[2-(2-amino-5-halogeno-, methylthio-, methylsulfinyl-, methylsulfonyl- and sulfothiazol-4-yl)-2(Z)-alkoxyiminoacetamido] cephalosporins and their antibacterial activity. Among the compounds prepared, 7 beta-[2-(2-amino-5-chlorothiazol-4-yl)-2(Z)- methoxyiminoacetamido]-3-(imidazo[1,5-a]-pyridinium-1-yl)methyl-3-cephem -4-carboxylate (14) showed good antibacterial activity against both Staphylococcus aureus including methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa, whereas the antibacterial activity against other Gram-negative bacteria was a slightly lower than that of 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3-(im ida zo [1,2-a]pyridinium (I-1) and imidazo[1,5-a]pyridinium (I-4)-1-yl)methyl-3-cephem-4-carboxylates.     

Studies on condensed-heterocyclic azolium cephalosporins. I. Synthesis and antibacterial activity of 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)- alkoxyiminoacetamido]-3-(imidazo[1,2-a]pyridinium-1-yl)methyl-3- cephem-4-carboxylates.

In our study of the structure-activity relationships of cephalosporins bearing quaternary ammonium groups at the 3 position, we postulated that delocalization of the azolium positive charge would lead to an expanded antibacterial spectrum and increased activity. Since quaternization of condensed-heterocyclic compounds such as imidazo[1,2-a]pyridine gives positive charge delocalization, 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-alkoxyiminoacetamido] cephalosporin derivatives (1-53) bearing various (imidazo[1,2-a]pyridinium-1-yl)methyl moieties at the 3 position were prepared and their antibacterial activity was determined. As expected, these cephalosporins exhibited potent activity against both Gram-positive and Gram-negative bacteria including Pseudomonas aeruginosa. These results imply that imidazo[1,2-a]pyridine is a quite useful substituent for improving antibacterial activity and spectrum. The structure-activity studies revealed that a favorable substituent on the imidazo[1,2-a]pyridine is the cyano radical at the 6 position of the ring, and ethoxyimino or 1-carboxy-1-methylethoxyimino groups are suitable for the alkoxyimino substituent. Among the cephalosporins tested, 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)- ethoxyiminoacetamido]-3-(6-cyanoimidazo[1,2-a]pyridinium -1-yl)methyl-3-cephem-4-carboxylate (45) and 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-(1- carboxy-1-methylethoxyiminoacetamido]-3-(6-cyanoimidazo[1,2- a] pyridinium-1-yl)methyl-3-cephem-4-carboxylate (49) showed good antibacterial activity.     

Studies on semi-synthetic 7 alpha-formamidocephalosporins. III. Synthesis and antibacterial activity of some 7 beta-[D-2-(aryl)-2-[(4-ethyl-2,3-dioxopiperazin-1-yl)carbonyl amino] acetamido]-7 alpha-formamidoceph-3-em-4-carboxylate derivatives

The synthesis and antibacterial activity of 7 beta-[D-2-(aryl)-2-[(4-ethyl-2,3-dioxopiperazin-1-yl) carbonylamino] acetamido]-7 alpha-formamidocephalosporins with various substituents at the C-3 position of the cephalosporin nucleus is described. Inhibition of Gram-positive and Gram-negative bacteria including beta-lactamase producing strains was observed with phenyl as the aryl residue. The 3,4-dihydroxyphenyl group further enhanced the activity against Gram-negative organisms; in this series, the 3-[(1-methyl-1H-tetrazol-5-yl)thiomethyl] and 3-[(1-carboxymethyl-1H-tetrazol-5-yl)thiomethyl] analogues (2 and 12b) exhibited exceptional activity against Gram-negative bacteria, including Pseudomonas aeruginosa.     

Studies on anti-MRSA parenteral cephalosporins. I. Synthesis and antibacterial activity of 7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)- hydroxyiminoacetamido]-3-(substituted imidaz

In order to improve the antibacterial activity of cefozopran (CZOP) against methicillin-resistant Staphylococcus aureus (MRSA), we initiated chemical modification to introduce a 2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)-hydroxyimino acetyl group at the C-7 position and a 3- or 6-substituted imidazo[1,2-b]pyridazinium or 5-substituted imidazo[1,2-a]pyridinium group at the C-3' position. Although this approach successfully enhanced the anti-MRSA activity of CZOP two to eight times, a slight decrease in the activity against Gram-negative bacteria including Pseudomonas aeruginosa was involved. Among the novel derivatives, 3-(6-aminoimidazo[1,2-b]pyridazinium-1-yl)methyl-7beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2(Z)hydroxyiminoacetamido]-3-cephem-4-carboxylate (44a) showed an excellent balance of activity against MRSA and Gram-negative bacteria.     

Studies on condensed-heterocyclic azolium cephalosporins. V. Synthesis and antibacterial activity of 3-(condensed-triazolo-pyridinium, -pyrimidinium, and -pyridazinium)-methyl cephalosporins.

As a part of our studies on cephalosporins bearing condensed-heterocyclic azolium methyl groups at the 3 position in the cephalosporin nucleus, we describe here the synthesis and antibacterial activity of 7 beta-[2-(2-aminothiazol-4-yl)2(Z)-methoxyiminoacetamido] cephalosporins (1-16, 7 beta-[2-(2-amino-5-chlorothiazol-4-yl)-2(Z)- methoxyiminoacetamido] cephalosporins (17,18) and 7 beta-[2-(5-amino- 1,2,4-thiadiazol-3-yl)-2(Z)-methoxyiminoacetamido) cephalosporins (19-23) containing a variety of condensed-heterocyclic triazolium methyl groups at the 3 position in the cephalosporin nucleus. These cephalosporins exhibited potent antibacterial activity, and it appears that condensed-heterocyclic triazolium as well as condensed-heterocyclic imidazolium rings are effective moieties for improving antibacterial activity and the spectrum of activity. Among the cephalosporins tested, 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3-(5- methyl[1,2,3]triazolo-[1,5-alpha]pyridinium-1-yl)methyl-3-cephem-4- carboxylate (9) and 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3-(6- methoxy[1,2,4]triazolo[1,5-alpha]pyridinium-1-yl)methyl-3-cephem-4- carboxylate (11) showed good antibacterial activity.     

Studies on condensed-heterocyclic azolium cephalosporins. II. Synthesis and antibacterial activity of 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-alkoxyiminoacetamido]-3-(condensed- heterocyclic azolium)methyl-3-cephem-4-carboxylates.

From our series of studies on cephalosporins bearing condensed-heterocyclic azolium methyl groups at the 3 position in the cephalosporin nucleus, we describe here the synthesis and antibacterial activity of 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-alkoxyiminoacetamido]ceph alosporins containing imidazo[1,5-a]pyridinium, imidazo[1,2-b]pyridazinium, imidazo[1,2-a]pyrimidinium, imidazo[1,2-c]pyrimidinium, and pyrazolo[1,5-a]pyridinium methyl groups at the 3 position. Among the cephalosporins tested, 7 beta-[2-(2-aminothiazol-4-yl)-2(Z)-methoxyiminoacetamido]-3- (imidazo[1,5-a]pyridinium-2-yl) (1), (imidazo[1,2-b]pyridazinium-1-yl) (2), and (pyrazolo[1,5-a]-pyridinium-1-yl) (3)methyl-3-cephem-4-carboxylates showed potent antibacterial activity and broad antibacterial spectrum. The antibacterial activity of these cephalosporins (1 approximately 3) was superior to that of ceftazidime (CAZ). These results imply that the delocalization of the positive charge of the imidazo[1,5-a]pyridinium, pyrazolo[1,5-a]pyridinium and imidazo[1,2-b]pyridazinium groups leads to an expanded antibacterial spectrum and increased activity and that these condensed-heterocyclic compounds as well as imidazo[1,2-a]pyridine are effective moieties for improving antibacterial activity and spectrum.     

Semisynthetic beta-lactam antibiotics. I. Synthesis and antibacterial activity of 7 beta-[2-aryl-2-(aminoacetamido)acetamido]-cephalosporins

The synthesis and in vitro structure-activity relationships of cephalosporins having dipeptides substituted with various aryl groups as the side chain at the C-7 position have been outlined. Of these compounds, 2-aminothiazol derivatives showed a broad spectrum of enhanced antibacterial activity, and 7 beta-[DL-2-(D-aminopropionamido)-2-(2-aminothiazol-4-yl)acet amido]-3- [(1-methyl-1H-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxyli c acid was the most balanced of these active derivatives with respect to both Gram-positive and Gram-negative strains.     

Synthetic cephalosporins. V. Synthesis and antibacterial activity of 3-alkylthio-7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(O-substituted oxyimino)acetamido]cephalosporins and related compounds

3-Alkylthio-7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(O-substituted oxyimino)acetamido]cephalosporins (6 and 7) and the 3-methoxy analogues (10) were prepared by coupling diphenylmethyl 7-amino-3-alkylthio-3-cephem-4-carboxylate (1 and 2) or diphenylmethyl 7-amino-3-methoxy-3-cephem-4-carboxylate with (Z)-2-(2-tritylaminothiazol-4-yl)-2-(O-substituted oxyimino)acetic acid (4), followed by deprotection and subjected to examination of antibacterial activities. The pivaloyloxymethyl esters (8 and 9) of the compounds (6 and 7) were also prepared and oral activities of these esters were compared with those of the parent compounds (6 and 7). The cephalosporins (6a-j and 7a-c) had potent and wide antibacterial spectra against Gram positive and Gram negative bacteria which were comparable to those of cefixime or cefteram. Among them, the cephalosporins (6f and 7c) and the pivaloyloxymethyl esters (8b and 9b) had good in vivo efficacy in mice against infections of Escherichia coli No. 29 and especially 8b showed high urinary recovery in mice.     

AS-924, a novel bifunctional prodrug of ceftizoxime.

To improve the oral absorption of ceftizoxime (CZX), 7beta-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]- 3-cephem-4- carboxylic acid, we synthesized and evaluated a novel series of bifunctional prodrugs, in which L-alanine was introduced into the aminothiazole-oxime moiety at the C-7 position of the various lipophilic esters of CZX. Among these prodrugs, pivaloyloxymethyl 7beta-[(Z)-2-(2-(S)-alanylaminothiazol-4-yl)-2-methoxyiminoa cetamido]-3-cephem-4-carboxylate hydrochloride (ceftizoxime alapivoxil, AS-924) was well absorbed after oral administration in experimental animals and showed potent therapeutic effects in mice infected with gram-positive and gram-negative bacteria.