Antibacterials. Synthesis and structure-activity studies of 3-aryl-2-oxooxazolidines. 1. The "B" group

Structure-activity relationships of diverse oxazolidinones for linezolid-resistant Staphylococcus aureus strains possessing the cfr methyltransferase gene or ribosomal mutations

Staphylococcal resistance to linezolid (LZD) is mediated through ribosomal mutations (23S rRNA or ribosomal proteins L3 and L4) or through methylation of 23S rRNA by the horizontally transferred Cfr methyltransferase. To investigate the structural basis for oxazolidinone activity against LZD-resistant (LZD(r)) strains, we compared structurally diverse, clinically relevant oxazolidinones, including LZD, radezolid (RX-1741), TR-700 (torezolid), and a set of TR-700 analogs (including novel CD-rings and various A-ring C-5 substituents), against a panel of laboratory-derived and clinical LZD(r) Staphylococcus aureus strains possessing a variety of resistance mechanisms. Potency against all strains was correlated with optimization of C- and D-rings, which interact with more highly conserved regions of the peptidyl transferase center binding site. Activity against cfr strains was retained with either hydroxymethyl or 1,2,3-triazole C-5 groups but was reduced by 2- to 8-fold in compounds with acetamide substituents. LZD, which possesses a C-5 acetamide group and lacks a D-ring substituent, demonstrated the lowest potency against all strains tested, particularly against cfr strains. These data reveal key features contributing to oxazolidinone activity and highlight structural tradeoffs between potency against susceptible strains and potency against strains with various resistance mechanisms.

Regioselective and stereospecific synthesis of enantiopure 1,3-oxazolidin-2-ones by intramolecular ring opening of 2-(Boc-aminomethyl)aziridines. Preparation of the antibiotic linezolid

The amide moiety of several enantiopure unactivated 1-aryl- or 1-alkylaziridine-2-carboxamides were reduced and then N-Boc-protected to afford enantiopure 2-(Boc-aminomethyl)aziridines, which were further converted into enantiopure 5-(aminomethyl)-1,3-oxazolidin-2-ones by means of a stereospecific and fully regioselective BF3.Et2O-promoted intramolecular nucleophilic ring opening. One of these oxazolidinones was transformed into the antibiotic linezolid through a CuI-catalyzed N-arylation reaction at its carbamate moiety.

Synthesis and antibacterial activity of substituted oxotriazolylphenyl oxazolidinones

A series of 3-(4'-(2''-alkyl-3''-oxy-1'',2'',4''-triazolyl)-phenyl)-5-substituted oxazolidinones was designed and synthesized for in vitro antibacterial activity testing against fourteen Gram-negative and six Gram-positive standard organisms. The minimum inhibitory concentration (MIC) was determined by agar dilution at concentrations of 0.10, 0.20, 0.39, 0.78, 1.56, 3.13, 6.25 microg/mL. Different alkyl groups at the 2''-position played an important role in the activity against Gram-positive organisms. (S)-3-(4'-(2''-ethyl-3''-oxy-1'',2'',4''-triazolyl)-phenyl)-5-acetamidomethyloxazolidinone was active against Staphylococcus epidermidis, Streptococcus pneumoniae, Streptococcus enteridis and Streptococcus nonhemolyticus, whereas 2''-methyl, 2''-propyl and 2''-n-butyl counterparts did not show activity at 6.25 microg/mL. Modification of the 5-substitutent of oxazolidinones also affected the activity against Gram-positive organisms. (S)-3-(4'-(2''-ethyl-3''-oxy-1'',2'',4''-triazolyl)-phenyl)-5-acetamidomethyloxazolidinones was approximately two fold more potent than 5-chloroacetamido, 5-dichloroacetamido and 5-trifluoroacetamido counterparts against Streptococcus enteridis. None of these compounds showed growth inhibition against fourteen Gram-negative organisms at 6.25 microg/mL.

Synthesis of novel oxazolidinone antimicrobial agents

The oxazolidinone class of antimicrobials represents a promising advance in the fight against resistant Gram-positive bacterial infections. Four novel oxazolidinone antimicrobial compounds, each containing a benzodioxin ring system, have been prepared. The general synthesis of each compound begins with the construction of a benzodioxin ring system containing a nitro substituent that ultimately becomes the nitrogen of the oxazolidinone ring. Three of the compounds utilize high yielding 'click chemistry' in their final step. The antimicrobial activities of the new oxazolidinones have been measured and the MIC against Staphylococcus aureus for one of the antimicrobials was determined to be 2-3 microg/mL, which is comparable to the well-known oxazolidinone, linezolid.

Synthesis, SAR and antibacterial studies on novel chalcone oxazolidinone hybrids

With an intention to synergise the antibacterial activity of chalcones and oxazolidinones, several hybrid compounds possessing both chalcone and oxazolidinone moieties were synthesized and tested for antibacterial activity. The hybrid molecules containing heterocycles instead of aromatic ring were found to be active. A SAR study with various heterocycles resulted in a lead molecule 20, which was converted to one of the potent antibacterial compounds 27.

Synthesis and Evaluation of Urea and Thiourea Derivatives of Oxazolidinones as Antibacterial Agents

Urea and thiourea derivatives of oxazolidinones were synthesized and their inhibitory activity (MIC) was determined on the bacterial strains which includes clinical isolates and quality control organisms. The structure activity relationships were studied and a 3D-QSAR model was built using Genetic Function Approximation. Interestingly found that electron withdrawing groups at the ortho position of the phenyl ring enhances the activity.

New carbon-linked azole oxazolidinones with improved potency and pharmacokinetics

Substitution of phenyl oxazolidinones with carbon-linked azoles resulted in the discovery of a new class of potent oxazolidinones that have excellent Gram-positive activity. In addition, replacement of the C-5 acetamide side chains with a 4-methyl triazole diminished monoamine oxidase activity. The synthesis and biological evaluation of these compounds are reported.

Antibacterial activity of pyrrolopyridine-substituted oxazolidinones: synthesis and in vitro SAR of various C-5 acetamide replacements

A series of pyrrolopyridine-substituted oxazolidinones containing various C-5 acetamide isosteres was synthesized and the structure-antibacterial activity relationships determined against a representative panel of susceptible and resistant Gram-positive bacteria.

Synthesis of 1-[3-(4-benzotriazol-1/2-yl-3-fluoro-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-3-substituted-thiourea derivatives as antituberculosis agents

In continuation of our research program for new antituberculosis drugs, we have designed, synthesized and evaluated antimycobacterial activity of new series of 1-[3-(4-benzotriazol-1/2-yl-3-fluoro-phenyl)-2-oxo-oxazolidin-5-ylmethyl]-3-substituted-thiourea derivatives against different Mycobacterium species i.e. M. tuberculosis, M. avium and M. intracellulare in an agar dilution method. Compound 17 exhibited excellent antimycobacterial activity (in vitro) against drug sensitive and resistant clinical isolates of M. tuberculosis. Its MIC value is equivalent to linezolid and superior to isoniazid against all these strains.

New potential antibacterials: a synthetic route to N-aryloxazolidinone/3-aryltetrahydroisoquinoline hybrids

A synthetic route to a new structural type of potential antibacterials, with a hybrid 3-aryltetrahydroisoquinoline-6,7-diol/N-aryloxazolidinone structure, is reported. The synthesis involves the successive construction of the 3-aryltetrahydroisoquinoline and 4-substituted oxazolidinone moieties, the latter taking advantage of the functionalization at the para position of the aryl group.

Convenient Synthesis of Oxazolidinones by the Use of Halomethyloxirane, Primary Amine, and Carbonate Salt

[reaction: see text] Primary amines reacted with carbonate salts (Na2CO3, K2CO3, Cs2CO3, and Ag2CO3) and halomethyloxiranes in the presence of a base such as DBU or TEA to give oxazolidinones in high yields. The use of K2CO3 among these carbonate gave the best yield in this synthesis. A reaction mechanism was proposed that the oxazolidinone was obtained from an oxazinanone intermediate via a bicyclo[2.2.1] intermediate. The present reaction can be widely applied to convenient synthesis of useful N-substituted oxazolidinones and chiral oxazolidinones.

Synthesis and antibacterial activity of novel (un)substituted benzotriazolyl oxazolidinone derivatives

A series of novel (un)substituted benzotriazolyl oxazolidinone derivatives has been synthesized and tested for in vitro antibacterial activities by MIC determination against a panel of susceptible and resistant Gram-positive and Gram-negative microorganisms, some of which are resistant to methicillin and vancomycin. Compounds 20, 21, 24, 29 and 30 from this series were found to be equipotent or more potent than linezolid in vitro.

New Drugs for Tuberculosis: Current Status and Future Prospects

This article reviews two classes of compounds that have advanced into phase II and III clinical trials, long-acting rifamycins and fluoroquinolones, and a number of other drugs that have entered or may enter clinical development in the near future.

A synthetic route to a novel type of conformationally constrained N-aryloxazolidinones

The synthesis of N-aryloxazolidinone 1, a conformationally constrained analog of linezolid embodying a tricyclic pyrrolo[1,2-a][4,1]benzoxazepine moiety as the N-aryl substituent, is reported. The synthetic route involves the successive construction of the pyrrole, oxazepine, and oxazolidinone rings, with incorporation of the isoxazolylamino moiety in the last synthetic steps.

Synthesis and antibacterial evaluation of oxazolidin-2-ones structurally related to linezolid

Compounds structurally related to the known antimicrobial drug linezolid were selected in order to evaluate the influence of electron-withdrawing properties and altered geometric features as a result of the N-substituent modification. After a preliminary study of molecular modeling, cinnamoyl-, pyridin- and pyrimidinoxazolidin-2-ones were synthesized. None of the new compounds showed antibacterial activity.

Synthesis and antibacterial activity of some aryloxy/thioaryloxy oxazolidinone derivatives

A series of aryloxy/thioaryloxy oxazolidinone derivatives has been synthesized and tested for in vitro antibacterial activity by MIC determination against a panel of susceptible and resistant Gram-positive and Gram-negative microorganisms, some of which are resistant to methicillin and vancomycin. Compounds 12a, 12b, 14a, and 14b from this series were found to be equipotent or more potent than linezolid in vitro.

Discovery of isoxazolinone antibacterial agents. Nitrogen as a replacement for the stereogenic center found in oxazolidinone antibacterials

A series of potential antimicrobial derivatives possessing bioisosteric replacements for the central oxazolidinone ring found in oxazolidinone antibacterials have been prepared. The design concept involved replacement of the requisite sp(3)-hybridized stereogenic center found at the 5-position of the oxazolidinone with a nitrogen atom. The synthesis and antibacterial activity of three such ring systems, the benzisoxazolinones, pyrroles, and isoxazolinones is described.

Synthesis and antibacterial activity of arylpiperazinyl oxazolidinones with diversification of the N-substituents

A series of 4-arylpiperazin-1-yl-3-phenyloxazolidin-2-one derivatives with diversification of the N-substituents such as methylene O-linked heterocycles, thioamide, dithiocarbamate, thiourea, and thiocarbamate were synthesized and evaluated as antibacterial agents. Their in vitro activities (MIC) were evaluated against MRSA and VRE resistant Gram-positive strains such as Staphylococcus and Enterococcus. Most of the compounds were more potent in vitro but less active in vivo than linezolid.

QSPR of 3-aryloxazolidin-2-one antibacterials

A QSPR treatment has been applied to a data set consisting of 60 3-aryloxazolidin-2-one antibacterials to relate the in vitro minimum inhibitory concentration (MIC) (required to inhibiting growth of S. aureus) with theoretical molecular and fragment descriptors. The treatment using codessa pro descriptors leads to a seven-parameter model with r2 = 0.820 and r2cv = 0.758.

New Antibacterial tetrahydro-4(2H)-thiopyran and thiomorpholine S-oxide and S,S-dioxide phenyloxazolidinones

Combinatorial libraries of N-acylated 5-(S)-aminomethyloxazolidinone derivatives of S-oxide and S,S-dioxide tetrahydro-4(2H)-thiopyranyl and thiomorpholine phenyloxazolidinone series have been synthesized on a solid phase and evaluated for antimicrobial activity. Several novel potent leads have been identified, including orally active oxazolidinones with enhanced activity against respiratory tract infection pathogens Haemophilus influenzae and Moraxella catarrhalis.

The effect of remote chirality on the antibacterial activity of indolinyl, tetrahydroquinolyl and dihydrobenzoxazinyl oxazolidinones

The oxazolidinones are promising agents for the treatment of infections caused by gram-positive bacteria, including multidrug-resistant strains. In ongoing studies we have discovered that a strategically placed chiral center of appropriate absolute configuration improves the antibacterial activity of indolinyl oxazolidinone analogues (gram-positive MIC's<0.5 microg/mL for the most potent congeners). The design, synthesis, antibacterial activity and pharmacokinetic profile of a selected series of alpha-methylated indoline derivatives and a related set of tetrahydroquinolyl and dihydrobenzoxazinyl analogues are discussed.

New classes of antibacterial oxazolidinones with C-5, methylene O-Linked heterocyclic side chains

Exploration of the structure-activity relationships of the traditional C-5 acetamidomethyl side chain of the oxazolidonone antibacterials has yielded new, potent series of compounds of which the first examples, the O-linked iosoxazoles are described in detail, leading to the selection of the pre-clinical candidate AZD2563.

Synthesis and in vitro activity of novel isoxazolyl tetrahydropyridinyl oxazolidinone antibacterial agents

A series of isoxazolyl tetrahydropyridinyl oxazolidinones with various substituents at the 3-position of the isoxazole ring have been synthesized and their in vitro antibacterial activities (MIC) were evaluated against several Gram-positive strains including the resistant strains of Staphyloccus and Enterococcus, such as MRSA and VRE. One of the most potent compounds synthesized, 4f, showed comparable or better activity against selected bacterial strains than those of linezolid and vancomycin.