Orally active esters of cephalosporin antibiotics. 3. Synthesis and biological properties of aminoacyloxymethyl esters of 7-[D(-)-mandelamido]-3-[[(1-methyl-1H-tetrazol-5-yl)thio]methyl]-3-cephem-4-carboxylic acid.

The synthesis of six amino acid acyloxymethyl esters of cefamandole (1), a semisynthetic broad-spectrum cephalosporin antibiotic, is described. These esters were examined as potentially useful orally active antibiotic prodrugs. When tested for oral efficacy against Streptococcus pyogenes C203 in mouse protection tests, the esters were not notably more active than lithium cefamandole. Further studies demonstrated that significant blood and urine levels of 1 were not obtained after dosing 2a, 2b, and 2f orally at 17 mg/kg in mice. A study of the stability to chemical hydrolysis and the possible relationship of hydrolysis to the lack of oral absorption of these esters is also presented.     

Orally active cephalosporins. I. Synthesis and structure-activity relationships of 7 beta-[2-(R)-amino-2-phenylacetamido]-3-(1H- 1,2,3-triazol-4-yl)alkylthiomethyl-3-cephem-4-carboxylic acid and related compounds]

The synthesis, antibacterial activity and oral absorbability of 7 beta-[2-(R)-amino-2-phenylacetamido]-3-(1H-1H-1,2,3-triazol- 4-yl)methylthiomethyl-3-cephem-4-carboxylic acid (1a) and related compounds (1b-p and 2) are described. The replacement of 1,2,3-triazole at the C-3 position of 1a with other heteroaromatics such as 1,2,4-triazole, imidazole and so on decreased its oral absorbability in mice (1b-j). The oral absorbability was also influenced by the spacer length between C-3 of cephem nucleus and C-4 of 1,2,3-triazole. The quantitative relationship between the bioavailability and the spacer length of cephalosporins (1a and 1k-p) is discussed. These results suggest that 1,2,3-triazole in the side chain at the C-3 position of cephems plays an important role in good oral absorption through its interaction with the transport system of small intestine.     

Oral absorption of cephalosporin antibiotics. 3. Synthesis and biological properties of 7 alpha-methoxy-7 beta-(arylacetamido)-3-chloro-3-cephem-4- carboxylic acids

A series of 7 alpha-methoxy-7 beta-amido-3-chloro-3-cephem-4-carboxylic acids was prepared and evaluated for biological activity. When compared with the parent 7-non-methoxy analogues, these new 7 alpha-methoxy-3-chloro cephalosporins displayed diminished antimicrobial activity.     

Orally absorbable cephalosporin antibiotics. 3. Preparation of biologically active R isomer of 7-(3-benzothienylglycylamido)deacetoxycephalosporanic acid

The methyl and isopropyl esters of (RS)-3-benzothienylglycine were resolved with (+)- and (-)-tartaric acid in acetonitrile to give the corresponding R and S salts. The R-salt 4 was hydrolyzed to (R)-3-benzothienylglycine (5). The amino group in 5 was protected with the Boc function and the protected R amino acid 6 coupled with the p-NB ester of 7-ADCA to give the diprotected cephalosporin 7. After removal of the Boc and p-NB groups, the R isomer of 7-(3-benzothienylglycylamido)deacetoxycephalosporanic acid (1) was obtained. The p-NB ester of epimeric cephalosporin 7 was separated by preparative chromatography into R and S isomers. After removal of the protective groups, the S epimer was isolated. The comparison of antibacterial activity of the R and S epimers and the RS mixture of cephalosporin 1 is reported.     

Potential fungicidal and bactericidal agents. Synthesis of certain 4-(2-amino-1,3,4-thiadiazol-5-yl)quinolines

The synthesis of some new 4-[2-alkyl (aryl or aralkyl) amino-1,3,4-thiadiazol-5-yl]-2-substituted quinolines is described. IR, UV, NMR and MS data of representative examples are discussed. Most of the compounds prepared showed a reasonable antifungal and antimicrobial activity.     

Synthesis and anticonvulsant properties of 3-(1,3,4-thiadiazol-2-yl) thiazolidin-4-ones.

A series of 2-substituted 3-(1,3,4-thiadiazol-2-yl)thiazolidin-4-ones were synthesized and evaluated for anticonvulsant activity in a genetic model of reflex epilepsy (sound-induced seizures in DBA/2 mice). The combination of preferred substituents in the 2-position coupled with the introduction of a mercapto group on the thiadiazole moiety led to a number of active compounds. The anticonvulsant activity of most derivatives is better than that of the clinically useful anticonvulsant sodium valproate and some of them appear to possess potencies in the same range as phenytoin and clobazam.     

7-氨基-3-(1-吡啶甲基)头孢烯酸(7-APCA)卤化物的合成路线

7-氨基-3-(1-吡啶甲基)头孢烯酸(7-APCA)卤化物是头孢他啶合成的重要中间体,笔者在查阅了大量的文献资料的基础上,综述了7-氨基-3-(1-吡啶甲基)头孢烯酸(7-APCA)卤化物合成方法的优点、缺点,同时阐述了笔者试验结果,以7-ACA为原料制备7-APCA卤化物的合成路线。     

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.     

Orally active esters of cephalosporin antibiotics. II. Synthesis and biological properties of the acetoxymethyl ester of cefamandole

The synthesis of the acetoxymethyl (AOM) ester of cefamandole (CM) is described. The sparingly soluble ester is shown to be well absorbed orally by mice, but only when administered in solution in a partially non-aqueous vehicle, 50% propylene glycol. Neither the ester in aqueous suspension nor the sodium salt of CM in solution is well absorbed orally. The rate of oral absorption of the ester from solution is very rapid as shown by the early peak time and shape of the plasma level curve. Oral bioavailability from solution is at least 60% and is apparently limited only by hydrolysis or precipitation of a variable portion of the ester dose in the intestinal lumen prior to absorption.     

The liquid chromatographic analysis and pharmacokinetics of the semi-synthetic cephalosporin 3-methyl-7-[4-(1,4,5,6-tetrahydro-2-pyrimidyl)-phenylacetamido]-delta 3-cephalosporanic acid (I)

A high-pressure liquid chromatographic method is described for the analysis of the cephalosporin 3-methyl-7-[4-(1,4,5,6-tetrahydro-2-pyrimidyl)-phenylacetamido]-delta 3-cephalosporanic acid (I) in human plasma and urine. The analysis was carried out on a reverse-phase column and the column effluent was monitored by UV absorption at 236 nm. The lower limits of detection are 0.5 micrograms ml-1 and 0.2 micrograms ml-1 for plasma and urine, respectively. The correlation coefficient for the analysis of this cephalosporin in serum was 0.966 in comparison with a microbiological assay. Plasma and urine levels of (I) in three volunteers given an i.v. dose (500 mg) of the compound have been measured by this method and pharmacokinetic evaluation of the results performed assuming a two-compartment open model. The plasma half-life of the cephalosporin was 0.55 +/- 0.18 h up to 1--2 h after dosing and 2.2 +/- 0.7 h thereafter. At steady-state, the volume of the central compartment was 8--20 l and the volume of distribution was 12--31 l. A comparison of total clearance with renal clearance suggested that 97 +/- 2.6% of the compound would be excreted unchanged via the kidney and this was consistent with that observed experimentally.     

New broad-spectrum cephalosporins with anti-pseudomonal activity. II. Synthesis and antibacterial activity of 7 beta-[2-acylamino-2-(4-hydroxyphenyl)acetamido]-3-[ (1-methyl-1H-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxylic acids

The influence of the chirality of the 7-acyl side chain and of various N-acyl moieties (A-CO-) on the in vitro activity of 7 beta-[2-acylamino-2-(4-hydroxyphenyl)acetamido ]-3-[(1-methyl-1H-tetrazol-5-yl)thiomethyl]ceph-3-em-4-carboxylic acids (6) was investigated. A cephalosporin having a 7-acyl side chain of S-configuration (6r) was only weakly active against Staphylococcus aureus and Klebsiella pneumoniae and was inactive against the other species tested. Among the various N-acyl moieties in the cephalosporins having a 7-acyl side chain of the R-configuration, the 4-hydroxypyridine-3-carbonyl moiety, unsubstituted or substituted with 5-bromo and/or 6-alkyl groups and the 4-hydroxy-1,5-naphthyridine-3-carbonyl moiety, unsubstituted or substituted with a 6-methyl and a 6-methoxy group gave the most active compounds. N-Ethylation of the 4-hydroxy-1,5-naphthyridine-3-carbonyl derivative and the 4-hydroxypyridine-3-carbonyl derivative (6p, 6q) resulted in a decrease of the in vitro activity.     

Orally active 2-(alkyloxycarbonyl)-2-alkylideneethyl esters of cephalosporins.

2-(Alkyloxycarbonyl)-2-alkylideneethyl esters of various aminothiazole-oxyimino cephalosporins have been synthesized and studied. They are useful alternatives to the currently existing orally active esters. Among the new esters synthesized, the 3'-azidomethyl cephem ester Ro 41-3399 (7k) presented an oral bioavailability superior to the corresponding pivaloyloxymethyl ester (9) in a rat model and was selected as a candidate for further evaluation.     

Synthesis of 3-(1,3,4-thiadiazol-2-yl)pyrazolo[1,5-a] pyrimidine derivatives as potential antimicrobial agents

The synthesis of some 3-(1,3,4-thiadiazol-2-yl)pyrazolo[1,5-a]-pyrimidine derivatives is performed by reacting 2-(3-amino-1,2-dihydro-5-oxo-5H-pyrazol-4-il)-1,3,4- thiadiazoles with 2,4-pentanedione, ethyl 3-oxobutyrate and diethyl ethoxymethylenemalonate. The antimicrobial activity of the synthesized compounds is reported.     

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.