共查询到20条相似文献,搜索用时 9 毫秒
1.
Pyrroles containing a 2,3-dicarbonyl substitution pattern are synthesized in one step via a three-component Hantzsch procedure. The normally difficult-to-access substrates are readily obtained in short reaction times and in moderate to good yields, giving pharmaceutically attractive products containing multiple handles for further elaboration. 相似文献
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Barclay GL Quiclet-Sire B Sanchez-Jimenez G Zard SZ 《Organic & biomolecular chemistry》2005,3(5):823-835
In model studies towards the synthesis of kirkine, the carbon skeleton was constructed using a radical cascade reaction. Two different approaches towards the synthesis have been examined as well as the regioselectivity of the radical cyclisation. 相似文献
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Abdelmadjid Debache Wassima Ghalem Ali Belfaitah Bertrand Carboni 《Tetrahedron letters》2009,50(37):5248-5250
An efficient one-step synthesis of 1,4-dihydropyridines in good to excellent yields via the triphenylphosphine-catalyzed Hantzsch three-component reaction of an aromatic aldehyde, ethyl acetoacetate and ammonium acetate is described. 相似文献
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P. Mahesh Kumar K. Siva KumarSrinivas Reddy Poreddy Pradeep Kumar MohakhudK. Mukkanti Manojit Pal 《Tetrahedron letters》2011,52(11):1187-1191
A new and one-pot synthesis of novel alkynyl/alkenyl/aryl (hetero)aryl substituted 3,4-dihydropyrimidin-2(1H)-one derivatives has been developed via a multi-component reaction involving sequential phosphorus acid-mediated solvent-free Biginelli followed by copper-free Sonogashira or Heck or Suzuki reaction. 相似文献
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Krebs A Ludwig V Pfizer J Dürner G Göbel MW 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):544-553
We present two complementary methods for the stereoselective synthesis of non-natural alpha-amino acids with aromatic or heteroaromatic side chains. One approach is based on the chemical transformation of methionine, whereas the other applies the stereoselective Myers alkylation of glycine. The resulting product types differ in the linker length between glycine and the aromatic substituent. Since methionine and pseudoephedrine are available in both absolute configurations, R- or S-configured enantiopure amino acids with either C(2) or C(3) linkers can be obtained on gram scales. In each case the key step of the synthesis is hydroboration of the unsaturated building blocks 9 and 17, followed by palladium-catalyzed Suzuki cross-coupling with aryl halides. Attention must in certain cases be paid to the stereochemical integrity when basic Suzuki conditions are applied. Our initial difficulties are reported as well as the final "racemization-proof" procedures. The protecting groups chosen for the alpha-amino acids should be compatible with solid-phase peptide synthesis. This was confirmed by the successful synthesis of a series of tripeptides. 相似文献
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Banerjee B Capps SG Kang J Robinson JW Castle SL 《The Journal of organic chemistry》2008,73(22):8973-8978
A set of second-generation DBFOX ligands possessing extended aryl or benzyl-type groups was synthesized. The requisite amino alcohols were either commercially available (DBFOX/Bn) or constructed via Sharpless asymmetric aminohydroxylation (DBFOX/Nap, DBFOX/ t-BuPh, DBFOX/Pip) or phase-transfer-catalyzed asymmetric alkylation (DBFOX/MeNap). Complexes of the ligands with Mg(NTf2)2 were evaluated as promoters of enantioselective radical conjugate additions to alpha,beta-unsaturated alpha-nitro amides and esters. Reactions employing the DBFOX/Nap ligand exhibited improved enantioselectivity relative to previously published additions mediated by DBFOX/Ph. However, the relatively modest increase in diastereomeric ratio suggests that our substrate-Lewis acid binding model, which was formulated based on results from DBFOX/Ph-promoted radical conjugate additions, is in need of revision. 相似文献
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The efficient synthesis of racemic 4α-acetonyl-2?,3?-dihydroxycyclohexane-1α-acetanilide (1) from cyclohex-2-enol demonstrates a potential strategy for the control of the stereochemistry of the four contiguous chiral carbon atoms in the pyran ring of pseudomonic acids. An intermediate containing both a secondary amide and a tertiary amide reacted with methyl lithium to give a product derived from exclusive nucleophilic attack at the tertiary amide. 相似文献
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[reaction: see text] The preparation of cyclopropene alpha-amino acids via the enantioselective desymmetrization of cyclopropene bis-carboxylic acid derivatives is described. The amino acids are stable to harsh reaction conditions, and a derivative has been incorporated into a tripeptide using conventional methods for peptide synthesis. 相似文献
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M. Z. Kassaee Hassan Masrouri Farnaz Movahedi 《Monatshefte für Chemie / Chemical Monthly》2010,36(1):317-322
Abstract
Zinc oxide nanoparticles are used as an effective and reusable catalyst for one-pot, four-component couplings of aldehydes, dimedone, active methylene compounds, and ammonium acetate to produce polyhydroquinoline derivatives under solvent-free conditions at room temperature. Compared with other methods, satisfactory results are obtained with high yields, short reaction times, and simplicity in the experimental procedure. The catalyst could easily be recycled and reused four times without noticeable decrease in catalytic activity. 相似文献12.
[reaction: see text] A strategy for the synthesis of the spirocyclic core of spirolucidine was explored through a model study. The diene 4a was prepared and photolyzed to give the desired [2 + 2] photoadduct 17 containing the correct relative stereochemistry corresponding to spirolucidine. 相似文献
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In model studies towards the synthesis of harringtonolide, the construction of the tropone moiety via arene cyclopropanation was investigated. The installation of the lactone ring was accomplished by way of a Diels-Alder cycloaddition of various indenones and a-pyones. The incorporation of the key bridge methyl group and subsequent control of its stereochemistry is also outlined. 相似文献
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Davies SG Garner AC Ouzman JV Roberts PM Smith AD Snow EJ Thomson JE Tamayo JA Vickers RJ 《Organic & biomolecular chemistry》2007,5(13):2138-2147
Sequential enolate alkylations of (S)-N(1)-methyl-5-methoxy-6-isopropyl-3,6-dihydropyrazin-2-one and (S)-N(1)-p-methoxybenzyl-5-methoxy-6-isopropyl-3,6-dihydropyrazin-2-one proceed with excellent levels of diastereoselectivity (>90% de) affording quaternary alpha-amino acids in high enantiomeric excess (>98% ee) after deprotection and hydrolysis. 相似文献
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Addition of Et(2)AlCN and i-PrOH to ketosulfinimines (N-sulfinyl imines) affords corresponding alpha-alkyl alpha-amino nitriles in moderate to good yields. The diastereoselectivity is largely dependent on the E/Z isomer ratio of the ketosulfinimine. Hydrolysis of the diastereomerically pure amino nitriles affords enantiopure alpha-alkyl alpha-amino acids in moderate to good yields. 相似文献
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A new method for the synthesis of chiral beta-branched alpha-amino acids based on a copper-mediated directed allylic substitution reaction with Grignard reagents is reported. This is the first case in which a delta-stereogenic center is controlling the diastereoselectivity of an o-DPPB-directed allylic substitution. Depending on the alkene geometry of the starting material either diastereomer, anti or syn, is accessible with good levels of acyclic stereocontrol. 相似文献
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Tuning properties by programming the surface functional group composition of surface-block dendrimers has been limited to dendrimers with only two types of surface functionality (i.e., surface-diblock dendrimers). The Passerini reaction provides dendrimer products from precursor dendrons in reasonable yields. This proof-of-principle experiment opens the door to making surface-triblock dendrimers. 相似文献
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Catalyzed by the nitrile hydratase and the amidease in Rhodococcus sp. AJ270 cells under very mild conditions, a number of alpha-aryl- and alpha-alkyl-substituted DL-glycine nitriles 1 rapidly underwent a highly enantioselective hydrolysis to afford D-(-)-alpha-amino acid amides 2 and L-(+)-alpha-amino acids 3 in high yields with excellent enantiomeric excesses in most cases. The overall enantioselectivity of the biotransformations of nitriles originated from the combined effects of a high L-enantioselective amidase and a low enantioselective nitrile hydratase. The influence of the substrates on both reaction efficiency and enantioselectivity was also discussed in terms of steric and electronic effects. Coupled with chemical hydrolysis of D-(-)-alpha-phenylglycine amide, biotransformation of DL-phenylglycine nitrile was applied in practical scale to produce both D- and L-phenylglycines in high optical purity. 相似文献