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Chiral Building Blocks (chiral + building_block)
Kinds of Chiral Building Blocks Selected AbstractsChemInform Abstract: A New Route for the Synthesis of (R)-Glyceraldehyde Acetonide: A Key Chiral Building Block.CHEMINFORM, Issue 24 2010K. Chandra Babu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Comparative Study of Cyanobacteria as Biocatalysts for the Asymmetric Synthesis of Chiral Building BlocksENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2006J. Havel Abstract The three representative cyanobacteria, Synechococcus PCC7942, Anabaena variabilis, and Nostoc muscorum, were studied for their ability to asymmetrically reduce the prochiral ketones 2,-3,-4,-5,-6,-pentafluoroacetophenone, ethyl 4-chloroacetate, 4-chloroacetophenone, and ethylbenzoylacetate to the corresponding chiral alcohols. Photosynthesis as well as respiration was applied for intracellular regeneration of the NAD(P)H cofactor. It was shown for the first time that all cyanobacteria were able to reduce the prochiral ketones asymmetrically without light for cofactor regeneration. By comparison of the cell specific product formation capacities of cyanobacteria with typical heterotrophic whole cell biocatalysts in batch processes, it is shown that comparable or, in some cases, better performances at high enantiomeric excess (ee > 99.8,%) are obtained. As a consequence of a generally strong product inhibition, in situ product removal must be applied in order to restore process efficiency when using cyanobacteria as biocatalysts. [source] Allylic Hydroxy Phosphonates: Versatile Chiral Building Blocks.CHEMINFORM, Issue 42 2005Antonette De la Cruz Abstract For Abstract see ChemInform Abstract in Full Text. [source] Preparation of Synthetically Useful Chiral Building Blocks , 5-Alkylated ,-Lactones via Catalytic Asymmetric Hydrogenation of 4-Oxo Esters.CHEMINFORM, Issue 14 2003G. Juszkiewicz Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Highly Efficient and Enantioselective Method for the Synthesis of Chiral Building Blocks Derived from meso-1,3-Propanediols.CHEMINFORM, Issue 24 2002Takeshi Oriyama Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: New Uses of Amino Acids as Chiral Building Blocks in Organic Synthesis.CHEMINFORM, Issue 6 2002Manfred T. Reetz Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis of an Inherently Chiral Calix[4]arene Amino Acid and Its Derivatives: Their Application to Asymmetric Reactions as OrganocatalystsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 12 2009Seiji Shirakawa Abstract The synthesis of an inherently chiral calix[4]arene amino acid as a chiral building block has been achieved in order for subsequent transformation to various types of inherently chiral calix[4]arenes. The optically pure, inherently chiral calix[4]arene amino acids were prepared by the separation of a diastereomeric mixture of calix[4]arene amino acid derivatives bearing a (R)-BINOL moiety. The separated optically pure calix[4]arene amino acid derivatives with a (R)-BINOL moiety were easily transformed to novel inherently chiral calix[4]arenes containing an amino alcohol structure or a quaternary ammonium moiety. These optically pure chiral calix[4]arenes were applied to asymmetric reactions as organocatalysts.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Synthesis of Murisolin, (15R, 16R, 19R, 20S)-Murisolin,A, and (15R, 16R, 19S, 20S)-16,19- cis -Murisolin and Their Inhibitory Action with Bovine Heart Mitochondrial Complex,ICHEMISTRY - AN ASIAN JOURNAL, Issue 6 2006Yasunao Hattori Abstract The asymmetric total synthesis of murisolin, (15R, 16R, 19R, 20S)-murisolin,A, and (15R, 16R, 19S, 20S)-16,19- cis -murisolin was performed by using an epoxy alcohol as a versatile chiral building block for synthesizing the stereoisomers of mono-THF annonaceous acetogenins. The inhibitory activity of these murisolin compounds was examined with bovine heart mitochondrial complex,I, and they showed almost the same activity. [source] Enhancement of the NAD(P)(H) Pool in Saccharomyces cerevisiaeENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2008A. Knepper Abstract Asymmetric biosyntheses allow for an efficient production of chiral building blocks. The application of whole cells as biocatalysts for asymmetric syntheses is advantageous because they already contain the essential coenzymes NAD(H) or NADP(H), which additionally can be regenerated in the cells. Unfortunately, reduced catalytic activity compared to the oxidoreductase activity is observed in many cases during whole-cell biotransformation. This may be caused by low intracellular coenzyme pool sizes and/or a decline in intracellular coenzyme concentrations. To enhance the intracellular coenzyme pool sizes, the effects of the precursor metabolites adenine and nicotinic acid on the intracellular accumulation of NAD(H) and NADP(H) were studied in Saccharomyces cerevisiae. Based on the results of simple batch experiments with different precursor additions, fed-batch processes for the production of yeast cells with enhanced NAD(H) or enhanced NADP(H) pool sizes were developed. Supplementation of the feed medium with 95,mM adenine and 9.5,mM nicotinic acid resulted in an increase of the intracellular NAD(H) concentration by a factor of 10 at the end of the fed-batch process compared to the reference process. The final NAD(H) concentration remains unchanged if the feed medium was solely supplemented with 95,mM adenine, but intracellular NADP(H) was increased by a factor of 4. The effects of NADP(H) pool sizes on the asymmetric reduction of ethyl-4-chloro acetoacetate (CAAE) to the corresponding (S)-4-chloro-3-hydroxybutanoate (S-CHBE) was evaluated with S.,cerevisiae,FasB,His6 as an example. An intracellular threshold concentration above 0.07,mM NADP(H) was sufficient to increase the biocatalytic S-CHBE productivity by 25,% compared to lower intracellular NADP(H) concentrations. [source] Synthesis, Structure and Magnetic Properties of a Tetranuclear Copper(II) Complex on the Basis of a 2-Substituted Glucopyranoside Schiff Base Ligand,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2006Anja Burkhardt Abstract Condensation of a derivatized 2-aminoglucose fragment with salicylaldehyde affords the new sugar-based Schiff base ligand benzyl 4,6- O -benzylidene-2-deoxy-2-salicylideneamino-,- D -glucopyranoside (H2L). The reaction of the dibasic ligand H2L with [Cu(CH3COO)2]·H2O leads to the formation of the tetranuclear copper(II) complex [{Cu(L)}4] (3) by a self-assembly process. The X-ray structural analysis of complex 3 which crystallizes together with two molecules of chloroform and one molecule of ethanol in the space group P212121 revealed for all copper atoms a NO3 coordination environment with a square-planar geometry. The tetranuclear molecule 3 consists of four chiral building blocks {Cu(L)} with the rare 2,3-coordination of the trans -configured donor atoms of the sugar backbone. The observed coordination mode of the building blocks exemplifies how chitosan-derived polysaccharide ligands can act as a chiral support for transition-metal complexes. The C-3 alcoholate oxygen atoms of the carbohydrate unit is bridging adjacent {Cu(L)} moieties resulting in an eight-membered Cu4O4 ring with a boat-like conformation. Temperature-dependent magnetic measurements of 3 indicate moderate antiferromagnetic interactions between the four copper(II) ions with a coupling constant of J = ,130 cm,1.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Simple Derivatives of Natural Amino Acids as Chiral Ligands in the Catalytic Asymmetric Addition of Phenylacetylene to AldehydesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2005Zhi-jian Han Abstract Optically active propargylic alcohols are important chiral building blocks in asymmetric synthesis, and asymmetric addition of terminal alkynes to aldehydes is one of the most important and interesting procedures by which to prepare these chiral building blocks. In this work we have identified some simple derivatives of (S)-proline and other natural amino acids as chiral ligands that can be combined with Ti(OiPr)4 and then used to catalyze the asymmetric addition of zinc acetylide, produced in situ by the reaction of phenylacetylene with diethylzinc, to aldehydes. The ee value was as high as 90,%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis of Chiral Imidazole Derivatives as Purine PrecursorsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2003Jerzy Suwi Abstract From commercially available chiral building blocks, we have developed methods for the syntheses of imidazole derivatives that contain a chiral alkyl substituent at ring atom. These compounds are suitable for further transformation into Nalkyl purine derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Enantioselective Hydrogenation of ,-Dehydroamino Acid Esters Catalyzed by Rhodium Complexes with Chiral Bisaminophosphine LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010Xianfeng Sun Abstract A highly efficient strategy for the synthesis of a series of chiral bisaminophosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for rhodium-catalyzed asymmetric hydrogenations of ,-dehydroamino acid esters. Up to 98% ee values were achieved for the enantioselective synthesis of aminocarboxylic acids and their derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules. [source] Room Temperature Highly Enantioselective Nickel-Catalyzed HydrovinylationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Nicolas Lassauque Abstract At room temperature, nickel catalysts based on the new phosphoramidite (11bR)- N -[(S)-1-(naphthalen-1-yl)ethyl]- N -[(S)-1-(naphthalen-2-yl)ethyl]dinaphtho[2,1- d:1,,2,- f][1,3,2]dioxaphosphepin-4-amine provide excellent selectivities for 3-arylbut-1-enes (93,99%) with high enantioselectivities (90,95% ee) and TOFs (up to 8300,h,1) in the hydrovinylation of electron-rich and electron-poor vinylarenes. Within a few minutes, useful chiral building blocks and intermediates can be synthesized using this practical catalytic system. [source] Axial Chirality Control by 2,4-Pentanediol for the Alternative Synthesis of C3*-TunePhos Chiral Diphosphine Ligands and Their Applications in Highly Enantioselective Ruthenium-Catalyzed Hydrogenation of ,-Keto EstersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Xianfeng Sun Abstract A highly efficient strategy for the synthesis of a series of C3*-TunePhos chiral diphosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for the ruthenium-catalyzed asymmetric hydrogenation of ,-keto esters. Up to 99% ee values were achieved for the enantioselective synthesis of ,-hydroxy acid derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules. [source] Enantioselective Benzylic Hydroxylation with Pseudomonas monteilii TA-5: A Simple Method for the Syntheses of (R)-Benzylic Alcohols Containing Reactive Functional GroupsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Yongzheng Chen Abstract Highly enantioselective benzylic hydroxylations of benzene derivatives (1,4) containing reactive functional groups were achieved for the first time with Pseudomonas monteilii TA-5 as biocatalyst, giving the corresponding (R)-benzylic alcohols 5,8 in 93,99% ee as the only products. Preparative biotransformations were demonstrated by the biohydroxylation of 1 and 2 with resting cells of P. monteilii TA-5 to afford (R)- 5 in 94% ee and 66% yield and (R)- 6 in 94% ee and 56% yield, respectively. The highly enantioselective biohydroxylations represent a simple access to (R)-benzylic alcohols containing reactive functional groups that are useful pharmaceutical intermediates and versatile chiral building blocks. [source] Primary Amine-Thioureas based on tert -Butyl Esters of Natural Amino Acids as Organocatalysts for the Michael ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Christoforos Abstract A new class of primary amine-thioureas based on tert -butyl esters of (S)-,-amino acids and (1S,2S)-diphenylethylenediamine was synthesized and their activity as catalysts in Michael additions was evaluated. Derivatives based on di- tert -butyl aspartate and tert -butyl O - tert -butyl threoninate provided the product of the reaction between trans- ,-nitrostyrene and acetone in quantitative yield and high enantioselectivity (87,91% ee). All the thioureas based on tert -butyl esters of amino acids catalyzed the reaction of nitroolefins with acetophenone with high enantioselectivity (92,98% ee). Thus, low-cost, commercially available tert -butyl esters of natural amino acids are very important chiral building blocks for the construction of novel chiral thioureas able to catalyze asymmetric Michael additions with high enantioselectivity. [source] A catalytic route to acyclic chiral building blocks: Applications of the catalytic asymmetric conjugate addition of organozinc reagents to cyclic enonesISRAEL JOURNAL OF CHEMISTRY, Issue 4 2001Richard B. C. Jagt Through the Cu-phosphoramidite-catalyzed asymmetric conjugate addition a number of chiral cyclic enones are available with high ee. Here we report the sequential conjugate addition to these enones as a route towards multisubstituted chiral cyclic ketones. A subsequent Baeyer,Villiger oxidation followed by ring-opening results in various linear synthons containing multiple stereocenters. This procedure represents a short, catalytic, and highly enantioselective route to a variety of acyclic chiral building blocks. [source] Synthesis of 6-Substituted 7-Bomoazabicyclo[2.2.1]heptanes via Nucleophilic Addition to 3-Bromo-1-azoniatricyclo[2.2.1.0]-heptane BromideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005Arnaud Gayet Abstract We describe herein an efficient method for the preparation of a functionalised bicyclic framework (6-substituted 7-bromo-aza-bicyclo[2.2.1]heptane) through the selective opening of the aziridium 2 with organocuprates in up to 90% yield. These interesting chiral building blocks were then utilised as novel ligands in the rearrangement of epoxides to afford chiral allylic alcohols. [source] Nature versus nurture in two highly enantioselective esterases from Bacillus cereus and Thermoanaerobacter tengcongensisMICROBIAL BIOTECHNOLOGY, Issue 1 2010Stephan Grosse Summary There is an increasing need for the use of biocatalysis to obtain enantiopure compounds as chiral building blocks for drug synthesis such as antibiotics. The principal findings of this study are: (i) the complete sequenced genomes of Bacillus cereus ATCC 14579 and Thermoanaerobacter tengcongensis MB4 contain a hitherto undescribed enantioselective and alkaliphilic esterase (BcEST and TtEST respectively) that is specific for the production of (R)-2-benzyloxy-propionic acid ethyl ester, a key intermediate in the synthesis of levofloxacin, a potent antibiotic; and (ii) directed evolution targeted for increased thermostability of BcEST produced two improved variants, but in either case the 3,5°C increase in the apparent melting temperature (Tm) of the mutants over the native BcEST that has a Tm of 50°C was outperformed by TtEST, a naturally occurring homologue with a Tm of 65°C. Protein modelling of BcEST mapped the S148C and K272R mutations at protein surface and the I88T and Q110L mutations at more buried locations. This work expands the repertoire of characterized members of the ,/,-fold hydrolase superfamily. Further, it shows that genome mining is an economical option for new biocatalyst discovery and we provide a rare example of a naturally occurring thermostable biocatalyst that outperforms experimentally evolved homologues that carry out the same hydrolysis. [source] Bifunctional-Thiourea-Catalyzed Diastereo- and Enantioselective Aza-Henry ReactionCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2006Xuenong Xu Dr. Abstract Bifunctional thiourea 1,a catalyzes aza-Henry reaction of nitroalkanes with N -Boc-imines to give syn -,-nitroamines with good to high diastereo- and enantioselectivity. Apart from the catalyst, the reaction requires no additional reagents such as a Lewis acid or a Lewis base. The N-protecting groups of the imines have a determining effect on the chirality of the products, that is, the reaction of N -Boc-imines gives R adducts as major products, whereas the same reaction of N -phosphonoylimines furnishes the corresponding S adducts. Various types of nitroalkanes bearing aryl, alcohol, ether, and ester groups can be used as nucleophiles, providing access to a wide range of useful chiral building blocks in good yield and high enantiomeric excess. Synthetic versatility of the addition products is demonstrated by the transformation to chiral piperidine derivatives such as CP-99,994. [source] A new definition of lifeCHIRALITY, Issue 3 2009James D. Carroll Abstract Chirality is often glossed over in theoretical or experimental discussions concerning the origin of life, but the ubiquity of homochiral building blocks in known biological systems demands explanation. Information theory can provide a quantitative framework for understanding the role of chirality in biology. Here I show how conclusions derived from information theory, in particular the concept of equivocation, can explain not only why chiral building blocks are necessary in living systems but also why a homochiral set of building blocks is necessary. These results lead to a new definition of life, and to the conclusion that the simplest form of life exists in the form of self-amplifying, autocatalytic reactions such as the Soai reaction. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||