Synthesis and biological properties of a new series of anti-MRSA beta-lactams; 2-(thiazol-2-ylthio)carbapenems

Z and E isomers of butenedioic acid with 2-amino-1,3-thiazole: 2-amino-1,3-thiazolium hydrogen maleate and 2-amino-1,3-thiazolium hydrogen fumarate

Maleic acid and fumaric acid, the Z and E isomers of butenedioic acid, form 1:1 adducts with 2-amino-1,3-thiazole, namely 2-amino-1,3-thiazolium hydrogen maleate (2ATHM), C(3)H(5)N(2)S(+) x C(4)H(3)O(4)(-), and 2-amino-1,3-thiazolium hydrogen fumarate (2ATHF), C(3)H(5)N(2)S(+) x C(4)H(3)O(4)(-), respectively. In both compounds, protonation of the ring N atom of the 2-amino-1,3-thiazole and deprotonation of one of the carboxyl groups are observed. The asymmetric unit of 2ATHF contains three independent ion pairs. The hydrogen maleate ion of 2ATHM shows a short intramolecular O-H...O hydrogen bond with an O...O distance of 2.4663 (19) A. An extensive hydrogen-bonded network is observed in both compounds, involving N-H...O and O-H...O hydrogen bonds. 2ATHM forms two-dimensional sheets parallel to the ab plane, extending as independent parallel sheets along the c axis, whereas 2ATHF forms two-dimensional zigzag layers parallel to the bc plane, extending as independent parallel layers along the a axis.

2-Bromo-1-(4-methoxy-phen-yl)ethanone

The title compound, C(9)H(9)BrO(2), prepared by the reaction of 4-methoxy-acetophenone and cupric bromide, , is approximately planar (r.m.s. deviation 0.0008 Å). In the crystal, weak inter-molecular aromatic C-H⋯O(carbon-yl) hydrogen-bonding inter-actions result in a one-dimensional chain structure.

Novel, Achiral 1,3,4-Benzotriazepine Analogues of 1,4-Benzodiazepine-Based CCK2 Antagonists That Display High Selectivity over CCK1 Receptors

A series of 1,3,4-benzotriazepine-based CCK(2) antagonists have been devised by consideration of the structural features that govern CCK receptor affinity and the receptor subtype selectivity of 1,4-benzodiazepine-based CCK(2) antagonists. In contrast to the latter compounds, these novel 1,3,4-benzotriazepines are achiral, yet they display similar affinity for CCK(2) receptors to the earlier molecules and are highly selective over CCK(1) receptors.

In vitro and in vivo antibacterial activities of SM-216601, a new broad-spectrum parenteral carbapenem

SM-216601 is a novel parenteral 1beta-methylcarbapenem. In agar dilution susceptibility testing, the MIC of SM-216601 for 90% of the methicillin-resistant Staphylococcus aureus (MRSA) strains tested (MIC(90)) was 2 microg/ml, which was comparable to those of vancomycin and linezolid. SM-216601 was also very potent against Enterococcus faecium, including vancomycin-resistant strains (MIC(90) = 8 microg/ml). SM-216601 exhibited potent activity against penicillin-resistant Streptococcus pneumoniae, ampicillin-resistant Haemophilus influenzae, Moraxella catarrhalis, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, with MIC(90)s of less than 0.5 microg/ml, and intermediate activity against Citrobacter freundii, Enterobacter cloacae, Serratia marcescens, and Pseudomonas aeruginosa. The therapeutic efficacy of SM-216601 against experimentally induced infections in mice caused by S. aureus, E. faecium, E. coli, and P. aeruginosa reflected its in vitro activity and plasma level. Thus, SM-216601 is a promising candidate for nosocomial bacterial infections caused by a wide range of gram-positive and gram-negative bacteria, including multiresistant pathogens.

SM-216601, a Novel Parenteral 1β-Methylcarbapenem: Structure-activity Relationships of Antibacterial Activity and Neurotoxicity in Mice

It has been reported that 2-(4-substituted thiazol-2-ylthio)-1beta-methyl-carbapenems exhibit potent activity against methicillin-resistant staphylococci (MRS) and vancomycin-resistant enterococci (VRE). In order to develop a novel broad-spectrum carbapenem, the structure-activity relationships of a series of 2-(4-tetrahydropyridinylthiazol-2-ylthio)-1beta-methylcarbapenems and 4-dihydropyrrolyl thiazole analogs were investigated with regard to their activity against Gram-positive and especially Gram-negative bacteria and also their convulsant activity, which is a major side effect concern of carbapenems. The introduction of substituent(s) on the dihydropyrrole moiety did not cause remarkable changes in anti-MRS and VRE activities, but tended to lower the anti-Gram-negative bacterial activity except in some cases of methyl group introduction. These substitutions did however cause a reduction of the convulsant activity, which was affected by the size and also the configuration of the substituent. In the case of SM-216601 (6), introduction of a methyl group brought about significant reduction in neurotoxicity while maintaining favorable anti-Gram-negative bacterial activity.

Synthesis and biological activity of 1β-methyl-2-[5-(2-N-substituted aminoethylcarbamoyl)pyrrolidin-3-ylthio]carbapenem derivatives

The synthesis of a new series of 1beta-methylcarbapenems having the substituted aminoethylcarbamoylpyrrolidine moiety is described. Their in vitro antibacterial activities against both Gram-positive including MRSA and Gram-negative bacteria were tested and the effect of substituent on the pyrrolidine ring was investigated. In particular, the compound 11g having piperazinyl urea moiety showed the most potent antibacterial activity and 11k exhibited excellent anti-MRSA.

In vitro and in vivo activities of novel 2-(thiazol-2-ylthio)-1beta-methylcarbapenems with potent activities against multiresistant gram-positive bacteria

SM-197436, SM-232721, and SM-232724 are new 1beta-methylcarbapenems with a unique 4-substituted thiazol-2-ylthio moiety at the C-2 side chain. In agar dilution susceptibility testing these novel carbapenems were active against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE) with a MIC(90) of </=4 micro g/ml. Furthermore, SM-232724 showed strong bactericidal activity against MRSA, in contrast to linezolid, which was bacteriostatic up to four times the MIC. SM-232724 showed good therapeutic efficacy comparable to those of vancomycin and linezolid against systemic infections of MRSA in cyclophosphamide-treated mice. The MICs of SM-197436, SM-232721, and SM-232724 for streptococci, including penicillin-intermediate and penicillin-resistant Streptococcus pneumoniae strains, ranged from </=0.063 to 0.5 micro g/ml. These drugs were the most active beta-lactams tested against Enterococcus faecium, and the MIC(90) s for ampicillin-resistant E. faecium ranged between 8 and 16 micro g/ml, which were slightly higher than the value for linezolid. However, time-kill assays revealed the superior bactericidal activity of SM-232724 compared to those of quinupristin-dalfopristin and linezolid against an E. faecium strain with a 4-log reduction in CFU at four times the MIC after 24 h of exposure to antibiotics. In addition, SM-232724 significantly reduced the numbers of bacteria in a murine abscess model with the E. faecium strain: its efficacy was superior to that of linezolid, although the MICs (2 micro g/ml) of these two agents are the same. Among gram-negative bacteria, these three carbapenems were highly active against Haemophilus influenzae (including ampicillin-resistant strains), Moraxella catarrhalis, and Bacteroides fragilis, and showed antibacterial activity equivalent to that of imipenem for Escherichia coli, Klebsiella pneumoniae, and Proteus spp. Thus, these new carbapenems are promising candidates for agents to treat nosocomial bacterial infections by gram-positive and gram-negative bacteria, especially multiresistant gram-positive cocci, including MRSA and vancomycin-resistant enterococci.

Synthesis and antibacterial activity of 1beta-methyl-2-(5-substituted thiazolo pyrrolidin-3-ylthio)carbapenem derivatives

The synthesis of a new series of 1beta-methylcarbapenems having the substituted thiazolopyrrolidine moiety is described. Their in vitro antibacterial activities against both Gram-positive including MRSA and Gram-negative bacteria were tested and the effect of substituent on the thiazole ring was investigated. A particular compound (28c) having 4'-amide substituted thiazole moiety showed the most potent antibacterial activity.

Dicationic dithiocarbamate carbapenems with anti-MRSA activity

A new class of 1 beta-methylcarbapenems bearing a doubly quaternarized 1,4-diazabicyclooctane (DABCO) substituted dithiocarbamate moiety at the C-2 side chain was prepared, and the biological profiles of the compounds, including in vitro and in vivo anti-MRSA activity and DHP-I susceptibility, were evaluated to identify a carbapenem derivative that was superior to BO-3482 (1). As a result, we discovered a 1 beta-methyl-2-[4-(4-carbamoylmethyl-1,4-diazabicyclo[2,2,2]octanediium-1-yl)methyl-1,2,3,6-tetrahydropyridinylthiocarbonylthio]carbapenem, 14a showing greater than 2-fold better anti-MRSA activity in a mouse infection model and 3-fold better DHP-I susceptibility as compared with BO-3482 (1).

Studies on the novel anti-staphyloccal compound nematophin

A number of analogues of the recently described compound nematophin were prepared and studied for antibacterial activity. The 2-phenyl derivative was found to exhibit exceptional activity against methicillin resistant Staphylococcus aureus (MRSA) whereas the isosteric benzimidazole analogue was much less active.

Discovery of novel trans-3,5-disubstituted pyrrolidinylthio-1beta-methylcarbapenems

Novel trans-3,5-disubstituted pyrrolidinylthio-1beta-methylcarbapenems were designed and synthesized to provide J-111,347 (1a) as the first example of an exceptionally broad-spectrum antibiotic, showing activity against methicillin-resistant Staphyloccocus aureus (MRSA) as well as Pseudomonas aeruginosa. Further derivation of 1a afforded J-111,225 (2a), J-114,870 (3a), and J-114,871 (3b). which showed improved safety profiles and retained broad-spectrum antibacterial activities.

Structure-activity relationships of trans-3,5-disubstituted pyrrolidinylthio-1beta-methylcarbapenems. Part 1: J-111,347 and related compounds

1Beta-methylcarbapenems having various 3,5-disubstituted pyrrolidinylthio-side chains at C-2 were designed and synthesized. Evaluation of their antibacterial activities indicated that J-111,347 (1a) is the first example of an extremely broad spectrum antibiotic showing activity against methicillin-resistant Staphylococcus aureus (MRSA) as well as Pseudomonas aeruginosa.

Antimicrobial effects of novel siderophores linked to beta-lactam antibiotics

As a strategy to increase the penetration of antibiotic drugs through the outer membrane of gram-negative pathogens, facilitated transport through siderophore receptors has been frequently exploited. Hydroxamic acids, catechols, or very close isosteres of catechols, which are mimics of naturally occurring siderophores, have been used successfully as covalently linked escorting moieties, but a much wider diversity of iron binding motifs exists. This observation, coupled to the relative lack of specificity of siderophore receptors, prompted us to initiate a program to identify novel, noncatechol siderophoric structures. We screened over 300 compounds for their ability to (1) support growth in low iron medium of a Pseudomonas aeruginosa siderophore biosynthesis deletion mutant, or (2) compete with a bactericidal siderophore-antibiotic conjugate for siderophore receptor access. From these assays we identified a set of small molecules that fulfilled one or both of these criteria. We then synthesized these compounds with functional groups suitable for attachment to both monobactam and cephalosporin core structures. Siderophore-beta-lactam conjugates then were tested against a panel of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus strains. Although several of the resultant chimeric compounds had antimicrobial activity approaching that of ceftazidime, and most compounds demonstrated very potent activity against their cellular targets, only a single compound was obtained that had enhanced, siderophore-mediated antibacterial activity. Results with tonB mutants frequently showed increased rather than decreased susceptibilities. suggesting that multiple factors influenced the intracellular concentration of the drugs.

Synthesis and activity of 2-(sulfonamido)methyl-carbapenems: discovery of a novel, anti-MRSA 1,8-naphthosultam pharmacophore

A series of 1beta-methyl carbapenems substituted at the 2-position with lipophilic, acyclic and cyclic (sulfonamido)methyl groups was prepared and evaluated for activity against resistant gram-positive bacteria. From these studies, the 1,8-naphthosultamyl group emerged as a novel, PBP2a-binding, anti-MRSA pharmacophore worthy of further exploration.

Synthesis and properties of 2-(naphthosultamyl)methyl-carbapenems with potent anti-MRSA activity: discovery of L-786,392

A series of 1beta-methyl-2-(naphthosultamyl)methyl-carbapenems bearing dicationic groups on the naphthosultamyl moiety was prepared and evaluated for activity against resistant gram-positive bacteria. Based on a combination of excellent in vitro antibacterial activity, acceptable mouse acute toxicity, and a desirable fragmentation pattern on beta-lactam ring opening, the analog 2g (L-786,392) was selected for extended evaluation.

Novel dithiocarbamate carbapenems with anti-MRSA activity

A new series of 1beta-methyl carbapenems, in which a disubstituted-aminothiocarbonylthio moiety was attached to the C-2 position of the carbapenem nucleus, were prepared and evaluated for anti-MRSA activity. These derivatives showed good in vitro antibacterial activity against high-level MRSA, and the finding of good affinity for PBP-2' supported these results. Some of the compounds having favorable protein-binding affinity showed excellent in vivo anti-MRSA activity.