The first part of the present review is devoted to the synthesis of 2-aroyl-3-aryl aziridines. Scientists are interested in these classes of heterocyclic compounds, first of all by their photochromic properties and high sensitivity towards UV-VIS irradiation. In addition, these compounds are interesting from the viewpoint of reactivity, chemo- and regio-selectivity, stereochemistry and many other. The last part is concerned with chemical behavior of 2-aroyl-3-aryl aziridines in numerous organic reactions including photochemical transformations, cycloadditions, rearrangements, regio- and stereo-selectivity, 1,3-diolar reaction, ring expansion, ring opening, deamination and other.
Due to growing number of bacterial strains acquiring resistance to the current arsenal of chemotherapeutic drugs, the search for novel anti bacterial agents continue to be a major area of research in many fronts.During the last decade,various groups have directed their efforts to synthesize various bioactive gamma-lactams. Modification of lactam ring has been playing a vital role in determining the bio-activities of these derivatives and so exploration of a novel methodology in a simple way is a pivotal focal point of research activity in bioorganic chemistry. Progress in the art of organic synthesis in the last decades has been achieved by marked advances in chemo-,regio-and stereoselective functional group transformations by using classical and newly developed reagents. The book entitled "Synthetic Studies on N-aryl- gamma-lactams" is an embodiment of research aimed at developing simple methodologies for selective functional group transformations of N-aryl- gamma-lactams and an effort towards the development of new synthetic strategies for conversion of N-aryl- gamma-lactams to substituted pyrrole and pyrroloquinoline derivatives.
Enzyme plays an important role in many biological and industrial processes. As a result, several chemical industries are employing biocatalysts for its promising applications in molecular, regio and enantio-selectivity and ultimately economy. The organic reactions performed by the enzymes are enormous and being the first rate-limiting step in the iterative cycle of setting up bio catalytic process. Present, book discusses cloning and characterization of metagenomic lipase. In general, the lipolytic enzymes are produced by variety of organisms. Lipases obtained from microorganisms are industrially more important, as they are more stable towards harsh processes. The gene encoding lipase was amplified with degenerate set of primers and cloned. The cloned product was expressed, purified and characterized biophysically and biochemically. Furthermore, the book discuses the use of directed evolution of the lipase employing error prone PCR/site directed mutagenesis. A mutant developed by directed evolution is discussed and characterized biophysically/biochemically, the results were compared with the wild type protein.
The administration of chiral compounds in an enantiomerically pure form, instead of racemic mixtures, become an important issue especially in the pharmaceutical and agrochemical industries due to the well established correlation between the biological activity and stereochemistry. Pure enantiomers could be formed by the asymmetric synthesis and /or the resolution of racemates. This could be achieved by the use of enzymes as chiral catalysts. The advantages of enzymes are their high stereo- (chiral), regio- (positional) and chemo- (functional group specific) selectivity. This selectivity offers several benefits like high catalytic efficiency, preservation of asymmetric centres, single step transformations, easier separation, mild operating conditions and fewer environmental problems. The organic reactions that are catalyzed by enzymes to give chiral bioactive organic compounds include, for example, reduction (e.g. by dehydrogenases, ketoreductases), oxidation (e.g. by monooxygenases, dioxygenases), hydrolytic (e.g. by lipases, esterases) reactions.
Biocatalysis shows high potential for the functionalization of unactivated C-H bonds at ambient conditions with absolute chemo-, regio-, and stereoselectivities being unrivalled by any chemical approach. In order to efficiently exploit nature’s toolbox towards an industrial implementation, engineering targets on the reaction as well as the catalyst level need to be identified and tackled in a concerted way.In this thesis, recombinant microbial cells containing the alkane monooxygenase AlkBGT from Pseudomonas putida GPo1 were applied for the w-functionalization of renewable fatty acid methyl esters (FAMEs). The resulting bifunctional products serve as building blocks for polymer syntheses. AlkBGT-containing Escherichia coli were shown to convert FAMEs with 5 to 12 carbon atoms in the alkyl chain giving the highest oxyfunctionalization activities (104 U gCDW -1 ) for nonanoic acid methyl ester. Kinetic studies revealed that AlkBGT catalyzes a three-step oxidation, yielding ?-alcohols, aldehydes and acids as products. In order to achieve ?-amino-functionalization, AlkBGT-based aldehyde formation was successfully coupled in recombinant E. coli with ?-transaminase catalysis (CV2025 from Chromobacterium violaceum), enabling the conversion of dodecanoic acid methyl ester (DAME) to 12-aminododecanoic acid methyl ester. Substrate uptake was identified as key factor limiting the conversion of the large and hydrophobic substrate DAME (1.4 U gCDW -1, 0.1 g L -1 h -1 ). Co-expression of the gene encoding the outer membrane protein AlkL relieved the uptake limitation and boosted the activities 62-fold to 87 U gCDW -1 allowing productivities of 4-8 g L -1 h -1 in two-liquid phase biotransformations. Furthermore, the latter reaction engineering concept enabled to control and govern product formation during AlkBGT-based multistep whole-cell biocatalysis. Overoxidation was prevented providing excess of substrate, yielding ?-alcohol as predominant product (up to 52 mM), whereas pronounced substrate limitation using bis(2-ethylhexyl)phthalate as organic carrier solvent resulted in almost exclusive acid accumulation (up to 93 mM). Introduction of the NAD(P)H-independent alcohol dehydrogenase AlkJ, which was shown to catalyze irreversible alcohol oxidation, into E. coli containing AlkBGT and AlkL enabled a shift towards the formation of overoxidized compounds in two-liquid phase biotransformations of DAME. This allowed the formation of the aldehyde as predominant product (up to 20 mM).Via catalyst and reaction engineering, this study sets the stage for the industrial implementation of recombinant microbial cells for terminal FAME functionalizations.
Palladium-mediated cyclization reaction has been recognized as one of the simplest and useful tool for the regio- as well as stereoselective synthesis of carbo- and heterocyclic compounds. In the multi-step synthesis of natural products Palladium-mediated C-H activation reaction is frequently used as one of the most important steps. Further heterocyclic moieties are present in natural products, pharmaceuticals, organic materials, and numerous functional molecules. Therefore, synthetic organic chemists are interested in developing new versatile and efficient syntheses of heterocycles. This book contains brief overview in the construction of heterocyclic rings in various ways under palladium-catalyzed C-H activation.
Lipases (E.C.22.214.171.124) of bacterial origin have been extensively screened and characterized due to their multifold advantages i.e. easy availability, bulk production, thermal stability, optimal performance in organic synthesis and amenability to molecular/ meta-genomic approaches.Lipases are indispensable for the bioconservation of lipids (triacylglycerol). They catalyze both the hydrolysis as well as synthesis of esters formed from glycerol and long chain fatty acids . These reactions usually proceed with higher regio- and/ or enantio-selectivity, thus making lipase an important biocatalyst in organic chemistryThis book will provide an insight into recent advancements and comparative account of novel lipase of Bacillus coagulans . The present book is divided into five chapters and each chapter describes production,purification, characterisation, immobilizations and its potential applications in detail. this book has been written for postgraduate biotechnology students and mainly for researcher working in the field of enzymes in general and Bacillus coagulans in specific.
Over the last decade the environmental setup has changed for synthetic organ ic chemists to a considerable degree. So far synthetic organic chemistry had focussed on methodology development which mainly deals with the develop ment of new reactions as well as new reagents and catalysts. These ought to be able to perform preferentially highly selective (chemo-, regio-and stereose lective) synthetic transformations, often applied in the context of complex and highly functionalized molecules. Except for the synthesis of peptides and oligonucleic acids, little attention has been spent on the question of how synthesis can be carried out in an envi ronment of sophisticated technologies which includes improved hardware. While peptides and oligonucleotides are conveniently prepared by Merrifield's solid phase technique, solution phase synthesis of most other synthetic targets have not been substantially replaced by this solid phase approach. Without discussing this aspect in detail it is obvious that today a renaissance of sophis ticated solution phase synthesis can be noted. Immobilization of reagents and particularly catalysts, an old concept indeed, recently returned back onto the stage and this is addressed in this volume of Topics in Current Chemistry in a broader sense.