Anupama Parmar

Advances in enzymatic transformation of penicillins to 6-aminopenicillanic acid (6-APA)

This article elaborates on the important recent developments in the enzymatic transformation of penicillins to 6-aminopenicillanic acid (6-APA), which is the basic raw material for the industrial production of semisynthetic penicillins such as amoxycillin and ampicillin. Particular emphasis is placed on the improvements in purification, stability, and immobilization of the enzymes, (i.e. penicillin acylases) used for these transformations.

Recent trends in enzymatic conversion of cephalosporin C to 7-aminocephalosporanic acid (7-ACA)

ABSTRACT: 7-Aminocephalosporanic acid (7-ACA) is the basic building block used in the synthesis of many important semisynthetic cephalosporin antibiotics that are of current interest in the biopharmaceutical industry with a share of about 29% of the estimated worldwide antibiotic market. This article describes the important recent developments for the biosynthesis of 7-Aminocephalosporanic acid (7-ACA) from cephalosporin C using the enzymatic route. Details of purification, stability, and immobilization of the enzymes used for this biotransformation are also described.

Ultrasound-promoted greener synthesis of 2H-chromen-2-ones catalyzed by copper perchlorate in solventless media.

Copper perchlorate is found to be a heterogeneous catalyst for an efficient and greener synthesis of 4-substituted 2H-chromen-2-ones via von Pechmann condensation of substituted phenols and beta-keto esters in solventless media with excellent yields using ultrasound irradiation. The present methodology offers several advantages such as excellent yields, simple procedure and milder conditions.

Trans-Esterification in Dry Media Using Ferric Perchlorate Adsorbed on Silica Gel

Abstract Adsorption of Fe(C104)3(H20)g onto chromatographic grade silica gel in the presence of ethyl acetate (to be used for trans-esterification) produces a supported reagent, Fe(C10,4)3(EtOAc)6/Si02-This reagent, has been found effective for the rapid and high yield of esters via trans-esterification on grinding in the presence of alcohols/carboxylic acids using pestle and mortar in the solid state.

Iron (III) perchlorate adsorbed on silica gel : A reagent for organic functional group transformations

Abstract Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic‐grade silica gel in the presence of organic solvents (S=water, acetonitrile, or lower fatty acids) produces a supported reagent, Fe(ClO4)3(S)6/SiO2. This reagent has been found to be effective for the rapid organic functional group transformations such as dimerization of alkynes, aromatic hydrocarbons, selective oxidation of thiols to disulfides, and transannular reactions in 1,5‐cyclooctadienes on grinding using pestle and mortar in the solid state.

One-pot Solvent-free Sonochemical Synthesis of 1-Amidoalkyl-2-naphthols

In recent years, organic synthesis involving greener processes, including solvent-free conditions, has been explored due to stringent environmental and economic regulations. 1 Homogeneous, liquid a...

Manganese Perchlorate–Catalyzed Greener Synthesis of 12-Aryl or 12-Alkyl-8,9,10,12-tetrahydrobenzo[α]xanthen-11-one Derivatives Under Ultrasonication

Abstract A greener and more efficient protocol for the synthesis of 12-aryl or 12-alkyl-8,9,10,12-tetrahydrobenzo[α]xanthen-11-one derivatives has been developed via one-pot, three-component reaction of aromatic aldehydes, 2-naphthol, and 1,3-cyclohexadione or 5,5-dimethyl 1,3-cyclohexadione using manganese perchlorate hydrate as a catalyst under ultrasonic irradiation. Good yield, shorter reaction time, simple workup procedure, and milder reaction conditions make this protocol efficient and environmentally benign. GRAPHICAL ABSTRACT

Ultrasound Promoted Cu(Clo4)2 Catalyzed Rapid Synthesis Of Substituted 1,2,3,4- Tetrahydropyrimidine-2-Ones & Hantzsch 1,4-Dihydropyridines In Dry Media

Copper perchlorate supported on bentonite clay as catalyst at room temperature gives 6-methyl-4-substituted-phenyl-2-oxo(thioxo)-l,2,3,4-tetrahydropyrimidine-5carboxylic acid ethyl esters & diethyl 2,6-dimethyl-4-substitutedphenyl-l,4dihydropyridine-3,5-dicarboxylate proficiently in high yields in solvent-less media under ultrasonic irradiation. Introduction Green chemistry protocols have shown significant potential as truly eco-friendly methodologies (1-2). Biginelli Compounds have exhibited pharmaceutical activities (3-6) whereas the 1,4-DHP motifs has been used as chemotherapeutic agents (7). The first synthetic method for the synthesis of l,2,3,4-tetrahydropyrimidine-2-ones (THPMs) was reported by Biginelli (8) under strongly acidic conditions producing THPMs, though in low yields. In view of the pharmaceutical significance of these compounds, many improved catalytic methods have been developed (9-13). In continuation of our studies (14) we wish to report an expedient procedure for the synthesis of l,2,3,4-tetrahydropyrimidine-2-one derivatives and Hanstzch 1,4 dihydropyridines from three-component condensation of aryl aldehydes, ethylacetoacetate and urea or thiourea or ammonium carbonate in solvent-less dry media (bentonite clay) supported-copper perchlorate as catalyst at room temperature under ultrasonic irradiation. Experimental Materials and Apparatus All melting points recorded are uncorrected, open capillary measurements, using sulphuric acid bath. IR spectra were recorded using KBr pellets on a Perkin-Elmer spectrophotometer, NMR spectra on AL-300F (Bruker) FT NMR spectrophotometer. Sonication was performed in ELMA, Transsonic T 310/H Ultrasonic cleaner (with a frequency of 35 KHz), Hans Schmidbauer GmbH & Co., Germany. The reactions were performed in open vessels. General procedure Synthesis of l,2,3,4-tetrahydropyrimidine-2-one derivatives la-f & Hantzsch 1,4 dihydropyridine derivatives 2a-f in solvent-less media: A mixture of aldehyde (0.010 mole), ethyl acetoacetate (0.015 mole) and urea or thiourea (0.012 mole) or ammonium carbonate (0.015 mole), in the presence of copper perchlorate (10% mmol) adsorbed on bentonite clay (5 gm) was placed in a sonicator under ultrasonic irradiation (completion of the reactions was monitored by TLC). To this crude reaction mixture was added ethyl alcohol (50 mL) and distilled water (5 mL). The mixture was stirred for 1 minute and then suction filtered. The spent reagent was

Copper Perchlorate Hexahydrate: An Efficient Catalyst for the Green Synthesis of Polyhydroquinolines under Ultrasonication

Copper perchlorate hexahydrate as an efficient catalyst was used for the synthesis of polyhydroquinolines by four-component condensation reaction of aldehyde, ethyl acetoacetate, dimedone, and ammonium acetate in excellent yields and short reaction times at room temperature under ultrasound irradiation. This novel synthetic method is especially favoured because it provides a synergy between copper perchlorate hexahydrate and ultrasound irradiation which offers the advantages of high yields, short reaction times, simplicity, and easy workup compared to the conventional methods reported in the literature.

SYNTHESIS OF HEXAHYDRO-1,3,5-TRIAZINES : A NEW APPROACH FROM N-SUBSTITUTED-ALPHA -AMINOISOTHIOCYANATES

Hexahydro-1,3,5-triazines have been prepared previously by the reaction of organic isocyanates and isothiocyanates with thiourea, alkali metal cyanates, amidines, imines, enamines and imidates. Solvent-free preparation of tris-pyrazoliy1,3,5-triazines as well as various camphor derived oxazolineazomethine imines and the synthesis of solution phase combinatorial library of 4,6-diamino1,2-dihydro-1,3,5-triazines were reported recently. Moreover, sequential aza-Wittig/cycloaddition/ringtransformation reactions leading to one-pot synthesis of novel 1,3,5 triazine derivatives are also known. In this paper, we report the synthesis of hexahydro1,3,5-triazines 3a-m from the reaction of N-substituted-α-aminoisothiocyanates 2a-m with toluene-2,4diisocyanate. N-substituted-α-amino-isothiocyanates 2a-m were obtained by the addition of ammonium thiocyanate/acetic acid to azomethines 1a-m.