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Objective: The main aim of the present work is to synthesize chloramphenicol impurity A (CLRMIMP- A) in the purest form and its subsequent characterization by using a panel of sophisticated analytical techniques (LC-MS, DSC, TGA, NMR, FTIR, HPLC, and CHNS) to provide as a reference standard mentioned in most of the international compendiums, including IP, BP, USP, and EP. The present synthetic procedure has not been disclosed anywhere in the prior art., Methods: A simple, cheaper, and new synthesis method was described for the preparation of CLRM-IMP-A. It was synthesized and characterized by FTIR, DSC, TGA, NMR (1H and 13C), LC-MS, CHNS, and HPLC., Results: CLRM-IMP-A present in drugs and dosage form can alter the therapeutic effects and adverse reaction of a drug considerably, it is mandatory to have a precise method for the estimation of impurities to safeguard the public health. Under these circumstances, the presence of CLRM-IMP-A in chloramphenicol (CLRM) requires strict quality control to satisfy the specified regulatory limit. The synthetic impurity obtained was in the pure form to provide a certified reference standard or working standard to stakeholders with defined potency., Conclusion: The present research describes a novel technique for the synthesis of pharmacopoeial impurity, which can help in checking/controlling the quality of the CLRM in the international markets., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

This year marks the 70th anniversary since Parke-Davis and Company announced the synthesis of chloramphenicol, the first naturally occurring antibiotic to be chemically generated in vitro for large-scale production. The effort was led by the chemist Mildred Rebstock, Ph.D., (1919 to 2011), who would turn 100 years old this year. Her accomplishment, at a time when very few chemists in the United States were women, was celebrated internationally. This commentary reviews her important contribution., (Copyright © 2019 American Society for Microbiology.)

This work presents a synthetic route to produce chloramphenicol esters by taking advantage the high enantio- and regio-selectivity of lipases. A series of chloramphenicol esters were synthesized using chloramphenicol, acyl donors of different carbon chain length and lipase Lip BA (lipase cloned from Bacillus amyloliquefaciens ). Among acyl donors with different carbon chain lengths, vinyl propionate was found to be the best. The influences of different organic solvents, reaction temperature, reaction time, enzyme loading and water content on the synthesis of the chloramphenicol esters were studied. The synthesis of chloramphenicol propionate (0.25 M) with 4.0 g L -1 of Lip BA loading gave a conversion of ~98% and a purity of ~99% within 8 h at 50 °C in 1,4-dioxane as solvent. The optimum mole ratio of vinyl propionate to chloramphenicol was increased to 5:1. This is the first report of B. amyloliquefaciens lipase being used in chloramphenicol ester synthesis and a detailed study of the synthesis of chloramphenicol propionate using this reaction. The high enzyme activity and selectivity make lipase Lip BA an attractive catalyst for green chemical synthesis of molecules with complex structures., Competing Interests: The authors declare no conflict of interest.

Chloramphenicol peptides were recently established as useful tools for probing nascent polypeptide chain interaction with the ribosome, either biochemically, or structurally. Here, we present a new 10mer chloramphenicol peptide, which exerts a dual inhibition effect on the ribosome function affecting two distinct areas of the ribosome, namely the peptidyl transferase center and the polypeptide exit tunnel. According to our data, the chloramphenicol peptide bound on the chloramphenicol binding site inhibits the formation of both acetyl-phenylalanine-puromycin and acetyl-lysine-puromycin, showing, however, a decreased peptidyl transferase inhibition compared to chloramphenicol-mediated inhibition per se. Additionally, we found that the same compound is a strong inhibitor of green fluorescent protein synthesis in a coupled in vitro transcription-translation assay as well as a potent inhibitor of lysine polymerization in a poly(A)-programmed ribosome, showing that an additional inhibitory effect may exist. Since chemical protection data supported the interaction of the antibiotic with bases A2058 and A2059 near the entrance of the tunnel, we concluded that the extra inhibition effect on the synthesis of longer peptides is coming from interactions of the peptide moiety of the drug with residues comprising the ribosomal tunnel, and by filling up the tunnel and blocking nascent chain progression through the restricted tunnel. Therefore, the dual interaction of the chloramphenicol peptide with the ribosome increases its inhibitory effect and opens a new window for improving the antimicrobial potency of classical antibiotics or designing new ones.

Encapsulation of more than one active pharmaceutical ingredient into nanocarriers such as liposomes is an attractive approach to achieve a synergic drug effect and less complicated dosing schedules in multi-drug treatment regimes. Liposomal drug delivery in acne treatment may improve drug efficiency by targeted delivery to pilosebaceous units, reduce adverse effects and improve patient compliance. We therefore aimed to co-encapsulate benzoyl peroxide (BPO) and chloramphenicol (CAM) into liposomes using the novel liposome processing method - dual asymmetric centrifugation (DAC). Liposomes were formed from soybean lecithin, propylene glycol and distilled water (2:1:2w/v/v ratio), forming a viscous liposome dispersion. Liposomes containing both drugs (BPO-CAM-Lip), single drug (BPO-Lip and CAM-Lip), and empty liposomes were prepared. Drug entrapment of BPO and CAM was determined by a newly developed HPLC method for simultaneous detection and quantification of both drugs. Encapsulation of around 50% for BPO and 60% for CAM respectively was obtained in both single-drug encapsulated formulations (BPO-Lip and CAM-Lip) and co-encapsulated formulations (BPO-CAM-Lip). Liposome sizes were comparable for all liposome formulations, ranging from 130 to 150nm mean diameter, with a polydispersity index <0.2 for all formulations. CAM exhibited a sustained release from all liposomal formulations, whereas BPO appeared retained within the liposomes. BPO retention could be attributed to its poor solubility. However, HaCaT cell toxicity was found dependent on BPO released from the liposomes. In the higher concentration range (4%v/v), liposomal formulations were less cytotoxic than the corresponding drug solutions used as reference. We have demonstrated that DAC is a fast, easy, suitable method for encapsulation of more than one drug within the same liposomes., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The highly enantio- and diastereoselective aldol reaction of isocyanoacetates catalysed by Ag2O and cinchona-derived amino phosphines applied to the synthesis of (-)- and (+)-chloramphenicol is described. The concise synthesis showcases the utility of this catalytic asymmetric methodology for the preparation of bioactive compounds possessing α-amino-β-hydroxy motifs.

In this study, we describe the synthesis of a full set of homo- and heterodimers of three intact structures of different ribosome-targeting antibiotics: tobramycin, clindamycin, and chloramphenicol. Several aspects of the biological activity of the dimeric structures were evaluated including antimicrobial activity, inhibition of in vitro bacterial protein translation, and the effect of dimerization on the action of several bacterial resistance mechanisms that deactivate tobramycin and chloramphenicol. This study demonstrates that covalently linking two identical or different ribosome-targeting antibiotics may lead to (i) a broader spectrum of antimicrobial activity, (ii) improved inhibition of bacterial translation properties compared to that of the parent antibiotics, and (iii) reduction in the efficacy of some drug-modifying enzymes that confer high levels of resistance to the parent antibiotics from which the dimers were derived.

Genomic studies revealed the absence of glutaminyl-tRNA synthetase and/or asparaginyl-tRNA synthetase in many bacteria and all known archaea. In these microorganisms, glutaminyl-tRNA(Gln) (Gln-tRNA(Gln)) and/or asparaginyl-tRNA(Asn) (Asn-tRNA(Asn)) are synthesized via an indirect pathway involving side chain amidation of misacylated glutamyl-tRNA(Gln) (Glu-tRNA(Gln)) and/or aspartyl-tRNA(Asn) (Asp-tRNA(Asn)) by an amidotransferase. A series of chloramphenicol analogs have been synthesized and evaluated as inhibitors of Helicobacter pylori GatCAB amidotransferase. Compound 7a was identified as the most active competitive inhibitor of the transamidase activity with respect to Asp-tRNA(Asn) (K(m)=2μM), with a K(i) value of 27μM., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Chloramphenicol (CAP) is a widely used broad-spectrum antibiotic. As the precursor of CAP, chloramphenicol bases are stereochemically pure agents and could be used as resolution agents, chiral catalysts and so on. This review summarizes these applications and discusses the structural modifications of chloramphenicol bases.

Herein we report a series of novel chloramphenicol amine derivatives as aminopeptidase N (APN)/CD13 inhibitors. All compounds were synthesized starting from commercially available (1S,2S)-2-amino-1-(4-nitrophenyl) propane-1,3-diol. The preliminary biological screening showed that some compounds exhibited potent inhibitory activity against APN. It should be noted that one compound, 13b (IC(50)=7.1 microM), possess similar APN inhibitory activity compared with Bestatin (IC(50)=3.0 microM).

While the resistance of bacteria to traditional antibiotics is a major public health concern, the use of extremely potent antibacterial agents is limited by their lack of selectivity. As in cancer therapy, antibacterial targeted therapy could provide an opportunity to reintroduce toxic substances to the antibacterial arsenal. A desirable targeted antibacterial agent should combine binding specificity, a large drug payload per binding event, and a programmed drug release mechanism. Recently, we presented a novel application of filamentous bacteriophages as targeted drug carriers that could partially inhibit the growth of Staphylococcus aureus bacteria. This partial success was due to limitations of drug-loading capacity that resulted from the hydrophobicity of the drug. Here we present a novel drug conjugation chemistry which is based on connecting hydrophobic drugs to the phage via aminoglycoside antibiotics that serve as solubility-enhancing branched linkers. This new formulation allowed a significantly larger drug-carrying capacity of the phages, resulting in a drastic improvement in their performance as targeted drug-carrying nanoparticles. As an example for a potential systemic use for potent agents that are limited for topical use, we present antibody-targeted phage nanoparticles that carry a large payload of the hemolytic antibiotic chloramphenicol connected through the aminoglycoside neomycin. We demonstrate complete growth inhibition toward the pathogens Staphylococcus aureus, Streptococcus pyogenes, and Escherichia coli with an improvement in potency by a factor of approximately 20,000 compared to the free drug.

A series of vinyl drug esters was synthesized using acyclovir and chloramphenicol with different carbon chain length acyl donors by alkaline protease from Bacillus subtilis and Lipozyme respectively, in non-aqueous medium. The corresponding vinyl drug derivatives were confirmed by nuclear magnetic resonance and infrared spectrometry. The influences of different organic solvents, reaction time, temperature, and content of water on synthesis of vinyl chloramphenicol esters were studied.

A seven-stage synthesis of a pyrrole analogue of chloramphenicol (9) is described. The compound exhibits a significant antibacterial activity, over the 3% to 50% range of the chloramphenicol activity: over the 6% to 100% range of the thiamphenicol activity and florfenicol.

[reaction--see text] The antibiotic (-)-choramphenicol has been synthesized in only four steps from p-nitro-benzaldehyde in optically pure form from an asymmetric catalytic aziridination reaction with a chiral catalyst prepared from triphenylborate and the (R)-VAPOL ligand. Catalysts generated from the VAPOL and VANOL ligands give much higher asymmetric induction than do catalysts prepared from 6,6'-diphenylVAPOL, BINOL, and BANOL ligands.

The seven-stage synthesis of a pyrrole analogue of chloramphenicol (VII) was described. The compound exhibits a significant antibacterial activity.

The seven-stage synthesis of a pyrrole analogue of chloramphenicol [IX] was described. The compound exhibits a significant antibacterial activity, over the 12-50% range of the chloramphenicol activity.

The paper describes the eleven stage synthesis of the derivative (XI) of 2,4-diamino-2,4-dideoxy-D-xylose, containing amino groups selectively substituted by two different acyls. The initial substrate was L-arabinose. The compound obtained, after removing the blocking groups, constitutes a semiproduct for the synthesis of the pyrrole analogue of chloromycetin by the Knorr method.

The toxic aldehyde derivative of chloramphenicol has previously been reported as a metabolic product only in the rat. Chloramphenicol-aldehyde has been synthesised and characterised and shown to exist in at least two forms, possibly due to rearrangement within the molecule. The authenticated compound has been used to identify chloramphenicol-aldehyde as a metabolic product excreted in the urine of children treated with chloramphenicol.

Four hybrid antibiotics combining structural features of chloramphenicol (1a), sparsomycin (2b), lincomycin (5c), and puromycin (6d)--lincophenicol (1c), chloramlincomycin (5a), sparsolincomycin (5b), and sparsopuromycin (6b)--were synthesized. They were investigated as inhibitors of several partial reactions of procaryotic and eucaryotic protein synthesis as well as potential antimicrobial agents. Lincophenicol (1c) was active as inhibitor of Escherichia coli ribosomal peptidyltransferase-catalyzed puromycin reaction. Both lincophenicol (1c) and sparsophenicol (1b) inhibited the binding of the iodophenol analogue of sparsomycin to E. coli ribosomes. The results are discussed in terms of a retro-inverso hypothesis advanced earlier for interpretation of biological activity of chloramphenicol (1a) and sparsophenicol (1b). Chloramlincomycin (5a) suppressed the growth of Streptococcus pyogenes with MIC 6.25 micrograms/mL.

The binary complex of diacetylchloramphenicol and chloramphenicol acetyltransferase (CAT) has been studied by a combination of isotope-edited 1H NMR spectroscopy and site-directed mutagenesis. One-dimensional HMQC spectra of the complex between 1,3-[2-13C]diacetylchloramphenicol and the type III natural variant of CAT revealed the two methyl 1H signals arising from each 13C-labeled carbon atom in the acetyl groups of the bound ligand. Slow hydrolysis of the 3-acetyl group by the enzyme precluded further analysis of this binary complex. It was possible to slow down the rate of hydrolysis by use of the catalytically defective S148A mutant of CATIII (Lewendon et al., 1990); in the complex of diacetylchloramphenicol with S148A CATIII, the chemical shifts of the acetyl groups of the bound ligand were the same as in the wild-type complex. The acetyl signals were individually assigned by repeating the experiment using 1-[2-13C],3-[2-12C]diacetylchloramphenicol, where only one signal from the bound ligand was observed. A two-dimensional 1H, 1H NOESY experiment, with 13C(omega 2) half-filter, on the 1,3-[2-13C]diacetylchloramphenicol/S148A CATIII complex showed a number of intermolecular NOEs from each methyl group in the ligand to residues in the chloramphenicol binding site. The 3-acetyl group showed strong NOEs to two aromatic signals which were selected for assignment. The possibility that the NOEs originated from the aromatic protons of diacetylchloramphenicol itself was eliminated by assignment of the signals from enzyme-bound diacetylchloramphenicol and chloramphenicol using perdeuterated CATIII. Examination of the X-ray crystal structure of the chloramphenicol/CATIII binary complex indicated four plausible candidate aromatic residues: Y25, F33, F103, and F158.(ABSTRACT TRUNCATED AT 250 WORDS)

Starting from p-perchloryl acetophenone we have synthesized the perchloryl analogue of chloramphenicol. The new compound is the first chloramphenicol analogue possessing a higher antimicrobial activity as chloramphenicol itself. It showed an about twofold activity against 18 different microbes in the hole plate diffusion test, compared with the parent compound.

Analogs of chloramphenicol were prepared for the first time in which the nitro group was replaced by hydroxylamine, nitroso, hydroxamic acid, methyl hydroxamate, and O-acetyl hydroxamate functional groups. These compounds were tested for antibiotic activity in order to determine whether the antibiotic activity of chloramphenicol is mediated by one or more of these potential metabolites of chloramphenicol. None of these analogs was as active as chloramphenicol against the four test organisms, and two of the compounds were essentially devoid of activity. The significance of these findings with regard to the importance of the nitro group to the biological activity of chloramphenicol is discussed.

The electrochemical characteristics of nitrosochloramphenicol have been studied in aqueous buffer systems (pH 7.1) using direct current (d.c.) and differential pulse polarography, cyclic voltammetry and coulometric techniques. Up to 4 charge-transfer steps can be identified. The first reduction step is reversible both chemically and electrochemically, the charge-transfer product showing no tendency to undergo further reaction on the electrochemical time-scale. In contrast, the second reduction step is irreversible, with the product undergoing a fast following reaction to yield a redox-active species which was detected by cyclic voltammetry. From the data and by comparison with related systems, two reduction mechanisms are possible and are discussed.

Bacterial resistance to the antibiotic chloramphenicol is normally mediated by chloramphenicol acetyltransferase (CAT), which utilizes acetyl coenzyme A as the acyl donor in the inactivation reaction. 3-(Bromoacetyl)chloramphenicol, an analogue of the acetylated product of the forward reaction catalyzed by CAT, was synthesized as a probe for accessible and reactive nucleophilic groups within the active site. Extremely potent covalent inhibition was observed. Affinity labeling was demonstrated by the protection afforded by chloramphenicol at concentrations approaching Km for the substrate. Inactivation was stoichiometric, 1 mol of the inhibitor covalently bound per mole of enzyme monomer, with complete loss of both the acetylation and hydrolytic activities associated with CAT. N3-(Carboxymethyl)histidine was identified as the only alkylated amino acid, implicating the presence of a unique tautomeric form of a reactive imidazole group at the catalytic center. The proteolytic digestion of CAT modified with 3-(bromo[14C]-acetyl)chloramphenicol yielded three labeled peptide fractions separable by reverse-phase high-pressure liquid chromatography. Each peptide fraction was sequenced by fast atom bombardment mass spectrometry; the labeled peptide in each case was found to span the highly conserved region in the primary structure of CAT, which had been tentatively assigned as the active site. The rapid, stoichiometric, and specific alkylation of His-189, taken together with the high degree of conservation of the adjacent amino acid residues, strongly suggests a central role for His-189 in the catalytic mechanism of CAT.