Antibacterial Agents: Solutions for the Evolving Problems of Resistance

β-Cristobalite (001) surface as 4-formaminoantipyrine adsorbent: First principle study of the effect on adsorption of surface modification

Silica based materials find applications as excipients and particularly as drug delivery agents for pharmaceutical drugs. Their performance can be crucially affected by surface treatments, as it can modify the adsorption (and release) of these formulations. The role of surface modification on the features of 4-formaminoantipyrine (FAA) adsorbed on β-cristobalite (001) surface is studied by means of simulations based on the Density Functional Theory (DFT). Starting from the results of FAA in interaction with a dehydroxylated surface; a fully hydroxylated surface and a functionalized surface with benzalkonium chloride (BC) surfactant have been added to study the configurational landscape. Calculations suggest that the trend for FAA preferential adsorption on silica surfaces is: dehydroxylated>hydroxylated>BC-functionalized. The potential for hydrogen bonding causes the main contribution to the bonding while dispersion forces present an additional contribution independently of whether the drug is hydrogen-bonded or BC-bonded to the surface. Adsorption takes mainly place through nitrogen atoms in the heterocyclic ring, the carbonyl and amine functional groups. Associated mode's shifts and concurrent changes in bond length are also observed showing accordance between electronic and geometrical structure results. BC surfactant reduces the number of formed H-bonds and lowers the attractive molecule-surface interaction being it useful to prevent particle agglomeration and could favor drug release in therapies that requires faster but controlled delivery.

Different molecular conformations co-exist in each of three 2-aryl-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamides: hydrogen bonding in zero, one and two dimensions

4-Antipyrine [4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one] and its derivatives exhibit a range of biological activities, including analgesic, antibacterial and anti-inflammatory, and new examples are always of potential interest and value. 2-(4-Chlorophenyl)-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamide, C19H18ClN3O2, (I), crystallizes with Z' = 2 in the space group P\overline{1}, whereas its positional isomer 2-(2-chlorophenyl)-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamide, (II), crystallizes with Z' = 1 in the space group C2/c; the molecules of (II) are disordered over two sets of atomic sites having occupancies of 0.6020 (18) and 0.3980 (18). The two independent molecules of (I) adopt different molecular conformations, as do the two disorder components in (II), where the 2-chlorophenyl substituents adopt different orientations. The molecules of (I) are linked by a combination of N-H...O and C-H...O hydrogen bonds to form centrosymmetric four-molecule aggregates, while those of (II) are linked by the same types of hydrogen bonds forming sheets. The related compound N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-(3-methoxyphenyl)acetamide, C20H21N3O3, (III), is isomorphous with (I) but not strictly isostructural; again the two independent molecules adopt different molecular conformations, and the molecules are linked by N-H...O and C-H...O hydrogen bonds to form ribbons. Comparisons are made with some related structures, indicating that a hydrogen-bonded R2(2)(10) ring is the common structural motif.

Synthesis and antimicrobial activity of some new heterocycles incorporating the pyrazolopyridine moiety

2-Cyano-N-(4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-yl)acetamide (2) was utilized as key intermediate for the synthesis of some new coumarin 3, pyridine 4, pyrrole 5, thiazole 8, pyrido[2',3':3,4]-pyrazolo-[5,1-c]triazine 7, and aminopyrazolo 10 compounds. 2-Cyano-N-(4,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-3-yl)-3-(dimethylamino)acrylamide (11) was synthesized and allowed to react with hydroxylamine, hydrazine, and guanidine to afford regioselectively the isoxazole 13, pyrazole 15, and pyrimidine 17 derivatives, respectively. The reaction of 11 with thiourea and/or with ethyl glycinate in basic medium afforded the regioisomeric pyrimidinethione 18 and 3,5-dioxo-1,4-diazepine-6-carbonitrile 23. All the synthesized products were tested and evaluated as antimicrobial agents.

Synthesis and antimicrobial activity of some new heterocycles incorporating antipyrine moiety

2-cyano-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamide (1) was utilized as key intermediate for the synthesis of some new coumarin 2, pyridine 3, pyrrole 4, thiazole 7, pyrido[2',3':3,4][pyrazolo[5,1-c]triazine and aminopyrazole 9. Treatment of aminopyrazole 9 with nitrous acid, 1,3-dicarbonyl compounds, enaminone, and DMF-DMA led to the formation of pyrazolo[3,4-d]triazine 10, pyrazolo[1,5-a]pyrimidines 11, 12, 14, and pyrazolo[3,4-d]pyrimidine 13, respectively. Condensation of 9 with isatin afforded Schiff base 16. The newly synthesized compounds were characterized by IR, 1H NMR and mass spectral studies. Representative compounds of the synthesized products were tested and evaluated as antimicrobial agents.

A Chiral Benzoquinolizine-2-carboxylic Acid Arginine Salt Active against Vancomycin-Resistant Staphylococcus aureus

There is an urgent medical need for novel antibacterial agents to treat hospital infections, specially those caused by multidrug-resistant Gram-positive pathogens. The need may also be fulfilled by either exploring antibacterial agents having new mechanism of action or expanding known classes of antibacterial drugs. The paper describes a new chemical entity, compound 21, derived from hitherto little known "floxacin". The choice of the entity was made from a series of synthesized prodrugs and salts of the active chiral benzoquinolizine carboxylic acid, S-(-)-nadifloxacin. The chemistry, physicochemical characteristics, and essential bioprofile of 21 qualifies it for serious consideration as a novel drug entity against hospital infections of multi-drug-resistant Staphylococcus aureus, and its progress up to clinical phase I trials in humans is described.

Novel inhibitors of bacterial protein synthesis: structure-activity relationships for 1,8-naphthyridine derivatives incorporating position 3 and 4 variants

Structure-activity relationships for a recently discovered novel ribosome inhibitor (NRI) class of antibacterials were investigated. Preliminary efforts to optimize protein synthesis inhibitory activity of the series through modification of positions 3 and 4 of the naphthyridone lead template resulted in the identification of several biochemically potent analogues. A lack of corresponding whole cell antibacterial activity is thought to be a consequence of poor cellular penetration as evidenced by the enhancement of activity observed for a lead analogue tested in the presence of a cell permeabilizing agent.