Discovery of FR166124, a novel water-soluble pyrazolo-[1,5-a]pyridine adenosine A1 receptor antagonist

Novel 3-(2-cycloalkyl and cycloalkenyl-3-oxo-2,3-dihydropyridazin-6-yl)-2-phenylpyrazo lo [1,5-a]-pyridines were synthesized and evaluated for their adenosine A1 receptor binding activities. In this series, FR166124 (3) was found to be the most potent and selective adenosine A1 receptor antagonist, and the double bond of the cyclohexenyl acetic acid group was essential for selectivity of A1 receptor binding. Furthermore, the solubility in water of the sodium salt of FR 166124 was high.

Anti-Helicobacter pylori agents. 2. Structure activity relationships in a new series of 2-alkylguanidino-4-furylthiazoles

SAR for antimicrobial activity against H. pylori was investigated in a new series of 2-alkylguanidino-4-furylthiazoles. Of the compounds obtained, cyclohexylmethyl and ethoxyethyl derivatives were identified as a novel class of anti-H. pylori agents which possessed potent and selective antimicrobial activity against H. pylori. These compounds also showed gastric antisecretory activity.

Anti-Helicobacter pylori agents. 1. 2-(Alkylguanidino)-4-furylthiazoles and related compounds

A series of 2-(alkylguanidino)-4-[5-(acetamidomethyl)furan-2-yl]thiazoles and related compounds were synthesized and evaluated for antimicrobial activity against Helicobacter pylori, inhibitory effect on gastric acid secretion, and histamine H2-receptor antagonist activity. Introduction of alkyl substituents on the guanidino moiety resulted in a significant increase in antimicrobial activity, which was associated with the alkyl chain length. Of the compounds obtained, the n-hexylguanidino derivative 13 demonstrated a 250-fold improvement in activity (MIC = 0.11 micrograms/mL) over the unsubstituted guanidino derivative 7. Alkyl-substituted guanidino derivatives also displayed gastric antisecretion and H2-antagonist activities. However, a simple correlation between the alkyl chain length and the activities was not found in these assays. Replacement of the guanidine with other bioisosteric groups (thiourea, urea, or (dimethylamino)methyl) resulted in loss of all activities tested. Thus the guanidino moiety was found to be essential for activity in this series of compounds.

Studies on 3'-quaternary ammonium cephalosporins--IV. Synthesis and antibacterial activity of 3'-(2-alkyl-3-aminopyrazolium) cephalosporins related to FK037

The synthesis and in vitro antibacterial activity of 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido] cephalosporins bearing various 2-alkyl-3-aminopyrazolium groups at the 3-position are described. Antibacterial activity against MRSA was affected by the nature of the substituent at the 2-position on the 3'-aminopyrazolium groups. Among the cephalosporins prepared in this study, 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]-3-[3-am ino-2-(2 -hydroxyethyl)-pyrazolio]methyl-3-cephem-4-carboxylate sulfate (23e, FK037) showed extremely potent broad-spectrum activity against both Gram-positive bacteria including MRSA, and Gram-negative bacteria including Pseudomonas aeruginosa. In particular, the in vivo activity against MRSA of FK037 was the highest of all the beta-lactam antibiotics tested.

Studies on 3'-quaternary ammonium cephalosporins--III. Synthesis and antibacterial activity of 3'-(3-aminopyrazolium) cephalosporins

The synthesis and in vitro antibacterial activity of 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]cephalos porins bearing N-mono or dialkyl and carbamoyl aminopyrazolium, and five- or six-membered rings fused to the 3-aminopyrazolium methyl groups at the 3-position, are described. Aminopyrazolium methyl cephalosporins (23e, f, i), with fused saturated and unsaturated rings were especially effective against Staphylococcus strains compared to 3-amino-2-methylpyrazolium methyl cephalosporin (1). Among the cephalosporins prepared in this work, 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetamido]-3-(4,5, 6, 7-tetrahydro-1-pyrazolo[1,5-a]pyrimidinio)methyl-3-cephem-4-carbox ylate (23f) showed a good balance of antibacterial activity against both Gram-positive bacteria including Staphylococcus aureus and Gram-negative bacteria including P. aeruginosa. An imidazopyrazolium group at the 3-position in, for example, cephalosporin (23i) was particularly effective for improving antibacterial activity against MRSA.

[Research and development of new oral cephems, cefixime and cefdinir]

This article reviews the structure-activity relationships, biological properties and synthesis of two new oral cephalosporin antibiotics, cefixime (CFIX) and cefdinir (CFDN). Our research into new oral cephalosporin antibiotics began in the late 1970's. The first goal of our research was to discover a new oral cephem possessing similar antibacterial activity and resistance to beta-lactamase as the 3rd generation injectable cephalosporins. We focused our attention on searching for a non-prodrug type cephem, that is, a new parent structure with high intrinsic absorption. We selected ceftizoxime (CZX) as a seed compound due to its relatively high excretion rate (8.5%) in the urine after oral administration to rats. We concentrated our research on the chemical modification of the oxime moiety in CZX based on our hypothesis for oral absorption, and discovered a lead compound with a carboxymethoxyimino group which displayed better urinary excretion (41.0%). Optimization studies led to a new oral cephem, CFIX. However, CFIX shows only low to moderate antibacterial activity against gram-positive bacteria such as S. aureus. Hence, the second goal of our research was to discover a new oral cephem with enhanced activity against gram-positive bacteria. From a consideration of structure-absorption relationships, we studied the activity and absorbability of cephems bearing other acidic functional groups at the oxime moiety of CFIX. As a result, we found a new oral cephem, CFDN with a hydroxyimino group at the 7-position. CFIX has excellent biological properties, displaying potent antibacterial activity against a wide range of gram-positive bacteria except S. aureus and gram-negative bacteria including opportunistic pathogens, high stability towards beta-lactamases and long acting efficacy. CFDN exhibits excellent and well balanced antibacterial activities against gram-positive and gram-negative bacteria. The pharmacokinetic of CFDN in healthy volunteers showed that serum levels were high enough to make CFDN as an effective antibacterial agent. The proposed mechanisms of intestinal absorption of CFIX and CFDN are briefly described. The efficient synthetic methods to CFIX and CFDN were achieved via a common intermediate, 7-amino-3-vinylcephalosporanic acid diphenylmethyl ester from 7-ACA.

[A new oral cephem, cefdinir: its structure-activity relationships and biological profile]

This article reviews structure-activity relationships and biological properties of a new oral cephem, cefidinir (CFDN). It also describes a hypothesis concerning the absorption mechanism from the intestine. Antibacterial activities and the oral absorption efficiencies were studied with regard to 3-vinyl cephalosporins with various 7-acyl side chains. From the study, 2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetyl group was selected and various 3-substituents were screened. As a result, it was found that the vinyl compound, CFDN, showed excellent antibacterial activity and good oral absorption in rats. In vitro and in vivo antibacterial activities, the affinity for PBPs and the stability to beta-lactamases revealed that CFDN had well balanced antimicrobial activities against Gram-positive and Gram-negative bacteria and good biological properties. The pharmacokinetics of CFDN in healthy volunteers showed that serum concentration and half life were good enough to make CFDN an effective therapeutic agent. The mechanism of intestinal absorption of CFDN and related oral cephems are discussed and a hypothesis for molecular recognition by the carrier protein in the intestine is proposed.

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.

[Studies on FK482 (Cefdinir). IV. Synthesis and structure-activity relationships of 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]- 3-substituted cephalosporin derivatives]

The synthesis of 7 beta-[(Z)-2-(aminothiazol-4-yl)-2-hydroxyiminoacetamido] cephalosporins (Ia-i) modified at the C-3 position of a cephem nucleus and the effect of the C-3 substituents on the antibacterial activity and oral absorbability are discussed. The cephems (Ie, h and i) having a C-3 substituent such as 1-propenyl, ethylthio and vinylthio group as well as FK482 (cefdinir) exhibited excellent antibacterial activities against both gram-positive and gram-negative bacteria. However, those compounds showed poor absorption rate after oral administration in rats. It is concluded that the vinyl moiety at the 3-position is necessary to display fairly oral absorptivity in a series of 7 beta-[(Z)-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]c eph ems.

Synthesis and antibacterial activity of 7 beta-[1-(2-aminothiazol-4-yl)-1-cyclopropanecarboxyamido]cephem derivatives

The synthesis and antibacterial activity of several 7 beta-[1-(2-aminothiazol-4-yl)-1-cyclopropanecarboxyamido]cep hem derivatives (1) are described. The structure-activity relationships of 1 are also presented.

Synthesis and biological activity of 3-vinylthio- and 3-vinylthiomethylcephem derivatives

The synthesis and biological properties of some 3-vinylthio- and 3-vinylthiomethylcephem derivatives are described. Both series possess potent antibacterial activity. Among them, 3-[(Z)-2-cyanovinylthiomethyl]cephem derivative was found to have an expanded antibacterial spectrum.