Unsaturated Ketoesters Research Articles

A highly diastereoselective three-component tandem 1,4-conjugated addition–cyclization reaction to multisubstituted pyrrolidines

A highly diastereoselective three-component tandem 1,4-conjugate addition-cyclization reaction of diazoacetophenones with anilines and unsaturated ketoesters was developed. The reaction provides general, easy, and highly efficient access to multisubstituted pyrrolidines in good yield with high diastereoselectivity.

ChemInform Abstract: Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N‐Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters.

AbstractThe use of Ti(O‐Pr)4 as a mild Lewis acid in combination with NHC catalysis is essential for the activation of α,β‐unsaturated aldehydes and promotion of the conjugate addition to ketoesters.

Inside Cover: Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N-Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters (Angew. Chem. Int. Ed. 7/2011)

Inside Cover: Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N-Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters (Angew. Chem. Int. Ed. 7/2011)

Innentitelbild: Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N‐Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters (Angew. Chem. 7/2011)

Innentitelbild: Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N‐Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters (Angew. Chem. 7/2011)

Lewis acid activated synthesis of highly substituted cyclopentanes by the N-heterocyclic carbene catalyzed addition of homoenolate equivalents to unsaturated ketoesters.

Lewis acid activated synthesis of highly substituted cyclopentanes by the N-heterocyclic carbene catalyzed addition of homoenolate equivalents to unsaturated ketoesters.

Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N‐Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters

Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N‐Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters

One-pot three-component tandem reaction of diazo compounds with anilines and unsaturated ketoesters: a novel synthesis of 2,3-dihydropyrrole derivatives

A facile synthesis of 2,3-dihydropyrrole derivatives has been achieved through the one-pot, three-component tandem reaction of diazo compounds with anilines and beta,gamma-unsaturated alpha-ketoesters in moderate to good yields.

ChemInform Abstract: Catalytic Enantioselective Hosomi—Sakurai Conjugate Allylation of Cyclic Unsaturated Ketoesters.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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.

Catalytic Enantioselective Hosomi–Sakurai Conjugate Allylation of Cyclic Unsaturated Ketoesters

Catalytic Enantioselective Hosomi–Sakurai Conjugate Allylation of Cyclic Unsaturated Ketoesters

Catalytic Enantioselective Hosomi–Sakurai Conjugate Allylation of Cyclic Unsaturated Ketoesters

Catalytic Enantioselective Hosomi–Sakurai Conjugate Allylation of Cyclic Unsaturated Ketoesters

Phe-Gly dipeptidomimetics designed for the di-/tripeptide transporters PEPT1 and PEPT2: synthesis and biological investigations.

A series of five Phe-Gly dipeptidomimetics containing different amide bond replacements have been synthesized in a facile way from the readily available unsaturated ketoester 1, and their affinities for the di-/tripeptide transporters hPEPT1 (Caco-2 cells) and rPEPT2 (SKPT cells) were tested. The compounds contained the amide bond isosteres ketomethylene (2a), (R)- and (S)-hydroxyethylidene (3a and 4a), and (R)- and (S)-hydroxyethylene (5a and 6a) to provide information on the conformational and stereochemical requirements for hPEPT1 and rPEPT2 affinity. The affinity studies showed that for rPEPT2 there is no significant difference in affinity between the ketomethylene isostere 2a and the natural substrate Phe-Gly (K(i) values of 18.8 and 14.6 microM, respectively). Also the affinities for hPEPT1 are in the same range (K(i) values of 0.40 and 0.20 mM, respectively). This corroborates earlier findings that the amide bond as such is not essential for binding to PEPTX, but the results also reveal possible differences in the binding of ketomethylene isosteres to hPEPT1 and rPEPT2. The trans-hydroxyethylidene and hydroxyethylene isosteres proved to be poor substrates for PEPTX. These results provide new information about the importance of flexibility and of the stereochemistry at the C(4)-position for this class of compounds. Furthermore, the intracellular uptake of 2a-4a in Caco-2 cells was investigated, showing a 3-fold reduction of the uptake of 2a in the presence of the competetive inhibitor Gly-Pro, indicating contribution from an active transport component. No active uptake of 3a and 4a was observed. Transepithelial transport studies also indicated active transport of 2a across Caco-2 monolayers.

The Synthesis of (±)-Wilforonide

The first synthesis of (±)-wilforonide has been completed in ten steps from commercially available starting materials. A high-yielding monomethylation of a reactive ketone enolate, a regioselective α-annulation of an unactivated α-substituted cyclohexanone, and a selective hydrogenation of the resulting unsaturated keto ester were key steps in the synthesis.

Development of the Juliá asymmetric epoxidation reaction. Part 2. Application of the oxidation to alkyl enones, enediones and unsaturated keto esters

Polyleucine-based systems have been used to catalyse the asymmetric oxidation of a variety of alkyl enones 1–4, 9–14, an enynone 16 and a dienone 17 to afford the corresponding epoxides 5–8, 18–26 in good to excellent yield and optical purity. A range of enediones 30–32, 34 and one unsaturated keto ester 33 have also been epoxidised stereoselectivley to afford optically active epoxides 35–39. The epoxidations were carried out with basic peroxide as the oxidant; the polyleucine catalyst was prepared from leucine N-carboxyanhydride using 1,3-diaminopropane, water (employing a humidity cabinet) or a polystyrene immobilised amine as the intiator. Preliminary mass spectral data on material derived from L-leucine and 1,3-diaminopropane (DAP-PLL) suggest that the catalyst consists of material that contains 22 ± 10 leucine residues.

Stereoselective access to polyfunctionalized decalins

As a model of a stereoselective approach to ajugareptansin 1, a versatile and straightforward access to polyfunctionalized cis or trans decalins is presented. It is based on a Lewis acid-mediated addition of furan to the unsaturated ketoester 3 followed by oxidative opening of the furan to give cis decalins by an aldolisation process. Selective epimerization at carbons 5 or 10 is described and allows the access to the trans ring geometry.

Synthesis of oxaspirolactones by manganic acetate promoted additions to exocyclic enol lactones

Oxidation of diverse β-diketones and β-ketoesters with manganic acetate generates intermediates which add to exocyclic enol lactones to afford spirocyclic lactone products. In the presence of added copper acetate the reaction pathway can be diverted to give unsaturated ketoesters.

Synthetic methods. 36. Utilization of ethyl 2-((phenylsulfonyl)methyl)acrylate for the synthesis of .alpha.-methylenevalerolactones

A two-step sequence is described for conversion of cyclic and acyclic ketone enolates into α-methylenevalerolactones. The first step involves Michael addition to ethyl α-((phenylsulfony)methyl)acrylate 1 with concomitant elimination of PhSO 2 and formation of unsaturated keto esters 2-7. In the next sequence chemoselective ketone reduction is usually followed by spontaneous lactonization of acidification. Contrary to the five- and six-membered ring systems, the cis-fused isomer predominates in the seven- and eight- membered ring compounds 12 and 13. Spiro α-methylenevalerolactones 17a,b are as well obtainable by a short sequence of steps from 2-oxocyclohexanecarboxylate and 1

ChemInform Abstract: Tandem Intramolecular Michael Addition and 1,3‐Dipolar Cycloaddition Reactions of Oximes. Versatile New Carbon‐Carbon Bond Forming Methodology.

AbstractThe unsaturated keto esters (I) and (V) are converted into nitrones such as (II) which perform cycloaddition reactions with N‐methyl maleimide (III) to give the polycyclic oxazolidine derivatives (IV), (VI), and (VII).

An improved method for 14C-labelling of farnesylacetic acid and its geranyl ester.

Farnesylacetic acid was efficiently labelled with 14C at the 5-position and gefarnate, a potent ulcer inhibitor, was prepared from it in radioactive form for use in metabolic studies. Condensation of [carbonyl-14C]acetyl chloride (5) with t-butyl 2-ethoxymagnesiomalonate (6) followed by acid-catalyzed deprotection and decarboxylation gave ethyl 3-oxo[3-14C]butanoate (8). Alkylation of the keto ester (8) with geranyl bromide (9) afforded the unsaturated keto ester (10), which was hydrolyzed and decarboxylated to give geranyl[2-14C]acetone (11). Grignard reaction of 11 with cyclopropylmagnesium bromide followed by treatment with hydrobromic acid yielded [4-14C]homofarnesyl bromide (13). Cyanation of 13 with potassium cyanide and subsequent hydrolysis gave [5-14C]farnesylacetic acid (1) in 6.1% yield from barium [14C]carbonate (3). Chlorination of 1 followed by esterification with geraniol afforded [5-14C]gefarnate (2) in 88% yield.

ChemInform Abstract: Synthesis of Substituted 1,2,3,4‐Tetrahydro‐6‐methyl‐2‐thioxo‐5‐pyrimidinecarboxylic Acid Esters.

AbstractThe hydrochloride of 2‐(4‐methoxybenzyl)‐2‐isothiourea (III) undergoes ring closure with the unsaturated keto esters (IV) to give the dihydropyrimidines (V) which are deprotected by treatment with trifluoroacetic acid and ethanethiol to form the tetrahydrothioxopyrimidines (VI).

Acylation of extended enolate ions from α-phenylthio (PhS-)crotonate esters

C-Acylation, like alkylation, occurs at the α opposition of the title compounds to give unsaturated keto-esters from which the PhS group may be removed