Quantitative structure-activity relationships of antibacterial agents, 7-heterocyclic amine substituted 1-cyclopropyl-6,8-difluoro-4-oxoquinoline-3-carboxylic acids

Synthesis, characterization, and antimicrobial evaluation of novel spiropiperidones

Novel spiro derivatives of piperidone 4a–f were synthesized, characterized, and screened against a panel of different bacterial and fungal strains. The study revealed the potential of these molecules for further development as antimicrobial agents.

Vosaroxin : a novel antineoplastic quinolone

INTRODUCTION

The antineoplastic quinolone derivative vosaroxin (SNS-595, Sunesis, South San Francisco, CA, USA) was first described in 2002. It represents a novel class of anticancer drugs and is currently in a Phase III clinical trial for relapsed and refractory acute myeloid leukemia (AML). AML is the most common form of acute leukemia in adults and is increasing in incidence due to the aging of the American population. Despite advances in diagnosis, prognostic prediction, and treatment in younger age groups, there has been little improvement in survival among patients over 60 years of age, who make up the majority of those affected.

AREAS COVERED

The development of vosaroxin, its mechanism of action, pharmacology, and metabolism, and the preclinical and clinical data to date will be covered.

EXPERT OPINION

Despite its structural dissimilarity, vosaroxin has mechanisms of action similar to the anthracyclines and anthracenediones already in use for the treatment of AML. However, unlike these agents, vosaroxin is not a P-gp substrate, appears to be unaffected by overexpression of P-gp or TP53 mutations, and may be useful in the treatment of AML, especially in the elderly.

Heterocycles [h]-fused onto 4-oxoquinoline-3-carboxylic acid, part VIII [1]. Convenient synthesis and antimicrobial properties of substituted hexahydro[1,4]diazepino[2,3-h]quinoline-9-carboxylic acid and its tetrahydroquino[7,8-b]benzodiazepine analog

[1,4]Diazepino[2,3-h]quinolone carboxylic acid 3 and its benzo-homolog tetrahydroquino[7,8-b]benzodiazepine-3-carboxylic acid 5 were prepared via PPAcatalyzed thermal lactamization of the respective 8-amino-7-substituted-1,4-dihydroquinoline-3-carboxylic acid derivatives 8, 10. The latter compounds were obtained by reduction of their 8-nitro-7-substituted-1,4-dihydroquinoline-3-carboxylic acid precursors 7, 9 which, in turn, were prepared by reaction of 7-chloro-1-cyclopropyl-6-fluoro-8-nitro-1,4-dihydroquinoline-3-carboxylic acid (6) with each of beta-alanine and anthranilic acid. All intermediates and target compounds were characterized using elemental analysis, NMR, IR and MS spectral data. The prepared targets and the intermediates have shown interesting antibacterial activity mainly against Gram positive strains. In particular, compound 8 showed good activity against S. aureus (MIC = 0.39 microg/mL) and B. subtilis (MIC = 0.78 microg/mL). Compounds 5a and 9 have also displayed good antifungal activity against C. albicans (MIC = 1.56 microg/mL and 0.78 microg/mL, respectively). None of the compounds tested showed any anticancer activity against solid breast cancer cell line MCF-7 cells or a human breast adenocarcinoma cell line.

Heterocycles [h]fused onto 4-oxoquinoline-3-carboxylic acid, part IV. Convenient synthesis of substituted hexahydro [1,4]thiazepino[2,3-h]quinoline-9-carboxylic acid and its tetrahydroquino[7,8-b]benzothiazepine homolog

Substituted [1,4]thiazepino[2,3-h]quinolinecarboxylic acid 3 is prepared by PPA-catalyzed thermal lactamization of the respective 8-amino-7-[(2-carboxyethyl)thio]-1,4-dihydroquinoline-3-carboxylic acid 9. The latter synthon is obtained by reduction of the 8-nitro-1,4-dihydroquinoline precursor 8 which, in turn, is made accessible via interaction of 3-mercaptopropionic acid with 7-chloro-1-cyclopropyl-6-fluoro-8-nitro-1,4-dihydroquinoline-3-carboxylic acid 7 in the presence of triethylamine. A benzo-homolog of 3, namely tetrahydroquino[7,8-b]benzothiazepine-3-carboxylic acid 6, is analogously prepared via the reaction of 2-mercaptobenzoic acid with 7, followed by reduction of the resulting 7-[(2-carboxyphenyl)thio]-8-nitro product 10 into the corresponding 8-amino derivative 11, and subsequent lactamization. The structures assigned to 3, 6 and 8-11 are based on microanalytical and spectral (IR, MS, NMR) data.

An Efficient Two-Step Synthesis of 3-Amino-1-Benzhydrylazetidine

A streamlined process for the synthesis of 3-amino-1-benzhydrylazetidine is described. Commercially available 1-benzhydrylazetidin-3-ol was reacted with methanesulfonyl chloride in the presence of triethylamine in acetonitrile, upon quench with water, the mesylate intermediate (3) was isolated by filtration. The wet filter cake was subsequently treated with ammonium hydroxide/isopropanol in a Parr reactor at ∼70°C. The procedure afforded the titled compound as mono acetate salt in 72–84% yield.

Hybrid antibacterials. DNA polymerase-topoisomerase inhibitors

Novel Gram-positive (Gram+) antibacterial compounds consisting of a DNA polymerase IIIC (pol IIIC) inhibitor covalently connected to a topoisomerase/gyrase inhibitor are described. Specifically, 3-substituted 6-(3-ethyl-4-methylanilino)uracils (EMAUs) in which the 3-substituent is a fluoroquinolone moiety (FQ) connected by various linkers were synthesized. The resulting "AU-FQ" hybrid compounds were significantly more potent than the parent EMAU compounds as inhibitors of pol IIIC and were up to 64-fold more potent as antibacterials in vitro against Gram+ bacteria. The hybrids inhibited the FQ targets, topoisomerase IV and gyrase, with potencies similar to norfloxacin but 10-fold lower than newer agents, for example, ciprofloxacin and sparfloxacin. Representative hybrids protected mice from lethal Staphylococcus aureus infection after intravenous dosing, and one compound showed protective effect against several antibiotic-sensitive and -resistant Gram+ infections in mice. The AU-FQ hybrids are a promising new family of antibacterials for treatment of antibiotic-resistant Gram+ infections.

Hydrazones of 1,2-benzisothiazole hydrazides: synthesis, antimicrobial activity and QSAR investigations

A series of hydrazones of 1,2-benzisothiazole hydrazides 1a-m, 2a-m, 3a-m, 4a-m, 5a-m as well as their cyclic (1 and 4) and acyclic (2, 3 and 5) 1,2-benzisothiazole parent hydrazides, were synthesised and evaluated as antibacterial and antifungal agents. All of the 2-amino-1,2-benzisothiazol-3(2H)-one derivatives, belonging to series I and IV, showed a good antibacterial activity against Gram positive bacteria. Most of them were active against yeasts too. Compounds 1 and 4, together with 1l, proved to be the most effective compounds. Quantitative structure-activity relationship (QSAR) investigation with a 2D-QSAR analysis was applied to find a correlation between different experimental or calculated physicochemical parameters of the compounds studied. A 3D-QSAR study was performed, applying Comparative Molecular Similarity Indices Analysis (CoMSIA) method, to derive quantitative models relating the structural features of 1,2-benzisothiazole derivatives 1, 1a-m and 4, 4a-m and their antimicrobial activity against Bacillus subtilis, resulted the most sensitive micro-organism.

Syntheses and biological activities of new N1-aryl substituted quinolone antibacterials

A series of quinolones with a systematically varied substitution at the phenyl ring at N1 has been synthesized. Three lipophilicity descriptors (log K, log P, Rm) and the pKa values have been determined as well as the microbiological activity: The MIC values for eight different strains of three Gram-positive and three Gram-negative species and the inhibitory concentrations of DNA supercoiling (IC90 and IC100) were determined. From a principal component and a QSAR analysis relationships between antibacterial activity concerning the whole-cell system and electronic properties as well as the length of the substituents at the phenyl rings could be derived. The activity in a cell-free system was governed by the lipophilicity and the width of the substituents. It is speculated that the quinolones take a defined place in the DNA gyrase-DNA complex which is characterized by polar amino acids. This is in agreement with findings from studies of mutant gyrases.