Suchandra Chakraborty

Brine-Mediated Efficient Benzoylation of Primary Amines and Amino Acids

Abstract Benzoylation of primary amines and amino acids is efficiently carried out in a brine solution using a stoichiometric amount of benzoyl chloride followed by trituration with aqueous saturated bicarbonate solution.

One-pot efficient reductive acetylation of aromatic nitro compounds

An efficient one-pot reductive acetylation of aromatic nitro compounds is developed without isolating the intermediate amine. The nitro compound is efficiently reduced by sodium borohydride and catalytic amount of Pd-C in MeOH-water media in presence / absence of alkali, and the amine thus generated is acetylated by acetic anhydride in situ in excellent yields through easy work-up. The technique unveils a new route for direct conversion of synthetically accessible nitro compounds to acetamido functionality and is reproducible in large scale. The method has been successfully extended in case of nitrosophenols as well.

Efficient acetylation of primary amines and amino acids in environmentally benign brine solution using acetyl chloride

AbstractAcetyl chloride is one of the most commonly available and cheap acylating agent but its high reactivity and concomitant instability in water precludes its use to carry out acetylation in aqueous medium. The present methodology illustrates the efficient acetylation of primary amines and amino acids in brine solution by means of acetyl chloride under weakly basic condition in the presence of sodium acetate and/or triethyl amine followed by trituration with aqueous saturated bicarbonate solution. This effort represents the first efficient use of this most reactive but cheap acetylating agent to acetylate amines in excellent yields in aqueous medium. This is a potentially useful green chemical transformation where reaction takes place in environment-friendly brine solution leading to easy work-up and isolation of the amide derivatives. Mechanistic rationale of this methodology is also important. Graphical AbstractAromatic and aliphatic primary amines and amino acids have been acetylated efficiently in brine solution with acetyl chloride under weakly basic conditions in the presence of sodium acetate and/or triethyl amine. The methodology demonstrates successful use of acetyl chloride as a substitute of acetic anhydride for the purpose of acetylation in aqueous medium.

Antibacterial Activity of Murrayaquinone A and 6-Methoxy-3,7-dimethyl-2,3-dihydro-1H-carbazole-1,4(9H)-dione

The antibacterial activity of Murrayaquinone A (10), a naturally occurring carbazoloquinone alkaloid, and 6-methoxy-3,7-dimethyl-2,3-dihydro-1H-carbazole-1,4(9H)-dione (11), a synthetic carbazoloquinone, both obtained during the development of the synthesis of Carbazomycin G, having unique quinone moiety, was studied against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas sp.) bacteria. Compound 10 showed antibacterial activities against both of Escherichia coli and Staphylococcus aureus whereas compound 11 indicated the activity against Staphylococcus aureus only. Both compounds 10 and 11 exhibited minimum inhibitory concentration (MIC) of 50 μg mL−1 against Staphylococcus aureus.

Solid-Phase Benzoylation of Phenols and Alcohols in Microwave Reactor: An Ecofriendly Protocol

Abstract An efficient solid-phase benzoylation of phenols and alcohols was developed under microwave irradiation. A stoichiometric amount of benzoyl chloride was sufficient to carry out the reaction. This benzoylation features short reaction time, good yields, and easy workup procedures. Furthermore, the scope of the reaction was extended to prepare 3,5-dinitrobenzoyl derivatives of alcohols. GRAPHICAL ABSTRACT

Monitoring the Competence of a New Keto-tetrahydrocarbazole Based Fluorosensor Under Homogeneous, Micro-Heterogeneous and Serum Albumin Environments

We present here a detailed photophysical study of a recently synthesised fluorophore 8-methyl-8,9-dihydro-5H-[1,3]dioxolo[4,5-b]carbazol-6(7H)-one. This is a synthetic precursor of bio-active carbazole skeleton Clausenalene. Spectroscopic investigation of the fluorophore has been carried out in different protic and aprotic solvents, as well as in binary solvent mixtures, using absorption, steady-state and time-resolved fluorescence techniques. This fluorophore is particularly responsive to the hydrogen bonding nature as well as polarity of the solvent molecules. When considered in micelles and β-cyclodextrin, this behaves as a reporter of its immediate microenvironment. Steady state and time resolved fluorometric and circular dichroism techniques have been used to explore the binding interaction of the fluorophore with transport proteins, bovine serum albumin and human serum albumin. The probable binding sites of the fluorophore in the proteinous environments have been evaluated from fluorescence resonance energy transfer study. Laser flash photolysis experiments also have been performed to observe the triplet excited state interaction between the fluorophore and albumin proteins.

In Vitro Activity of Synthesized 6-Chloro-2-methyl-1H-carbazole- 1, 4(9H)-dione against Methicillin-Resistant Staphylococcus aureus

The antimicrobial activity of synthesized 6-chloro-2-methyl-1H-carbazole-1,4(9H)-dione and 6- chloro-3-methyl-1H-carbazole-1,4(9H)-dione were studied against Escherichia coli (MTCC 42), Bacillus subtilis (MTCC 121), Staphylococcus aureus (MTCC 96), methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas sp.(MTCC 6199). 6-Chloro-2-methyl-1H-carbazole-1,4(9H)-dione having methyl substituent at C-2 and electron withdrawing chloro group at C-6 exhibited the remarkable antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) with MIC value of 50 µg/mL and against Staphylococcus aureus (MTCC 96) with MIC value of 100 µg/mL. However, 6-chloro-3-methyl-1H-carbazole-1,4(9H)-dione bearing methyl substituent at C-3 with chloro group at C-6 does not exhibited any antimicrobial activity against these pathogenic bacteria.

Isolation and Characterization of Pseudomonas sp. STM 997 from Soil Sample having Potentiality to Degrade 3,6-Dimethyl-1-keto-1,2,3,4-tetrahydrocarbazole: A Novel Approach

A pure colony of a bacterium from contaminated soil was isolated by exploiting 3,6-dimethyl-1-keto-1,2,3,4–tetrahydrocarbazole, a novel carbazole derivative, having indole moiety as well as 3-methyl functionality both in aromatic and hydro-aromatic moiety, as a sole source of carbon and energy. Taxonomical studies, biochemical analysis, and 16S rDNA sequence analysis indicated that the isolated strain has close similarity with Pseudomonas sp. Thin-layer chromatography followed by HPLC and mass spectroscopic study indicates that the isolated Pseudomonas sp. STM 997 degrades 3,6-dimethyl-1-keto-1,2,3,4–tetrahydrocarbazole, and this strain may be useful in the bioremediation of environments contaminated by the compounds containing carbazole moiety with methyl substituents at various reactive sites. This study also provides an evidence in favor of the suggested biodegradation of 3-methylcarbazole to carbazole in plants.