Direct introduction of a benzoyloxy substituent at the C-4 position of β-lactams

The copper-promoted reaction of β-lactams with t-butyl perbenzoate results in benzoyloxylation of the azetidin-2-one ring at the C-4 position. There is no competing reaction at the C-3 position, but reaction at exocyclic carbon α to nitrogen competes with ring substitution.     

Oxalic acid as a simple and efficient organocatalyst for three-component synthesis ofα-amino nitriles

A simple,efficient,and general method has been developed for the synthesis ofα-amino nitriles.Oxalic acid as a BrФnsted acid promotes the addition of TMSCN to various imines(generated in situ).     

A simple protocol for the synthesis of triazole-linked cyclic glycopeptidomimetics: a sequential Ugi-MCR and azide–alkyne cycloaddition approach

Sequential combination of Ugi-MCR and click chemistry has been employed for the synthesis of triazole linked cyclic glycopeptidomimetics. The protocol employs Poc-amino alkyl isonitriles, sugar-1-amines, azido acids, and simple aldehydes as precursors. The dual nature of the propargyloxycarbonyl (Poc) group was explored for amine protection as well as cycloaddition with an azide. All the cyclic glycopeptidomimetics are isolated and characterized.     

Acylation of Meldrum’s acid with arylacetic acid imidazolides as a convenient method for the synthesis of 4-aryl-3-oxobutanoates

C-Acylation of Meldrum’s acid by (het)arylacetic acids in ethanol in the presence of 1,1′-carbonyldiimidazole leads to ethyl 4-(het)aryl-3-oxobutanoates in high yields.     

Cyclic β-enaminoesters decarboxylation with boric acid: A convenient synthesis of cyclic imines

Δ¹-pyrrolines, Δ¹-piperideines and 1-aza 1-cycloheptenes are formed in good yields from the decarboxylation of alkylated cyclic β-enaminoesters with boric acid.     

Diphenylparabanic acid as a synthon for the synthesis of α-diketones and α-ketocarboxylic acids

Diphenylparabanic acid was found to react with >2 equiv of organolithiums at -78 °C to effectively give the corresponding symmetrical α-diketones. However, upon treatment with 1 equiv of organolithium, the parabanic acid gave mainly 5-substituted 5-hydroxyimidazolidine-2,4-diones. On the other hand, Grignard reagents were less reactive toward the parabanic acid at low temperature, and selectively gave the corresponding 5-hydroxyimidazolidine-2,4-diones even if more than 1 equiv of the reagents was used. A tandem process in which the parabanic acid was first reacted with a Grignard reagent and then reacted in one-pot with an organolithium effectively gave the unsymmetrical α-diketone. 5-Substituted 5-hydroxyimidazolidine-2,4-diones were useful as versatile precursors for preparing α-ketocarboxylic acids as well as unsymmetrical α-diketones.     

A sulfonic acid functionalized ionic liquid as a homogeneous and recyclable catalyst for the one-pot synthesis of α-aminophosphonates

A sulfonic acid functionalized ionic liquid is used as a Brønsted acid catalyst for the one-pot, three-component synthesis of α-aminophosphonates from aldehydes and ketones at room temperature in water. This homogeneous catalytic procedure is simple and efficient and the catalyst can be reused at least six times without any noticeable decrease in catalytic activity.     

Glyoxylic acid as catalyst： A simple selective synthesis of 1,2-disubstituted benzimidazoles in aqueous media

Glyoxylic acid （5 mol%） performs as a novel highly water-soluble catalyst for the synthesis of 2-aryl-l-arylmethyl-lH- benzimidazoles from a wide range of substituted o-phenylenediamines and various substituted aldehydes in good to excellent isolated yields （85-95%） using water as solvent at ambient temperature. The remarkable advantages offered by this method are easily and inexpensive available catalyst, simple procedure, mild conditions, much faster （20--40 rain） reactions and excellent yields of products.     

A stereoselective synthesis of an α-substituted α-amino acid as a substructure for the construction of myriocin

A synthetic route to the protected quaternary α-amino acid 2 with a hydroxylated side chain has been achieved. The key transformations are the diastereoselective substrate-controlled epoxidation of allylic alcohol 4; a highly stereoselective oxidation–reduction protocol, and the excellent regioselective isomerization of the oxazolidinone ring to give an oxazinanone skeleton in derivative 3. The carboxylic acid 2 obtained represents the polar substructure, which is present in myriocin 1.     

Ring expansion of cyclic β-amino alcohols induced by diethylaminosulfur trifluoride: synthesis of cyclic amines with a tertiary fluorine at C3

As the replacement of a hydrogen atom by a fluorine atom in a compound can have an important impact on its biological properties, the development of methods allowing the introduction of a fluorine atom is of great importance. The scope and limitations of the ring expansion of cyclic 2-hydroxymethyl amines induced by diethylaminosulfur trifluoride (DAST) to produce cyclic β-fluoro amines was studied as well as the enantioselectivity of the process.     

A new modification of the Friedländer synthesis. A simple route to 2-aminoquinoline-3-carboxylic acid and its derivatives

A new version of the Friedländer synthesis of 2-aminoquinoline-3-carboxylic acid and its derivatives from stable 2-tosylaminobenzaldehyde or its morpholinal was proposed.     

A simple and cost-effective synthesis of sulfated β-cyclodextrin and its application as chiral mobile phase additive in the separation of cloperastine enantiomers

Journal of Inclusion Phenomena and Macrocyclic Chemistry - A simple and cost-effective method for the synthesis of sulfated β-cyclodextrin, one of the most widely used chiral mobile phase...     

Superbase promoted synthesis of dienamides as useful intermediates for the synthesis of α-ketoamides, γ-lactams and cyclic imino ethers

Alkoxydienamides 2 have been synthesized exploiting the reactivity of α,β-unsaturated acetals 1 with isocyanates in the presence of Schlosser's superbase LIC-KOR. In a mild acidic medium, 2 can then be promptly converted both into α-ketoamides 3 and into substituted 2-pyrrolidinones 4 or imino ethers 5 by choosing the appropriate experimental conditions.     

Effects of substituent and catalyst on the intramolecular Povarov reaction—synthesis of chromenonaphthyridines

2-(N-Alkenyl-N-aryl)aminochromone-3-carbaldehyde undergoes intramolecular Povarov reaction with aromatic amines in the presence of Ph₃P·HClO₄ to produce chromenonaphthyridine. The effects of substituent and catalyst have been studied. The substituent on the alkenyl part of aminochromone controls the mode of reaction as well as the stereochemistry of the product.     

A simple new general synthesis of macrocyclic ketones: A new entry to the synthesis of exaltone and (±)-muscone

We describe an efficient new synthesis of 15-membered cyclic ketones, exaltone and (±)-muscone, based on a three-carbon annelation of cyclic ketones followed by the regioselective radical cleavage of the fused bond of the resulting bicyclic systems.     

Polyvinylsulfonic acid as a novel Brønsted acid catalyst for the synthesis of bis(indolyl)methanes

Abstract

Polyvinylsulfonic acid as a novel, biodegradable, and efficient Brønsted acid catalyst for the reaction of indoles with aldehydes to obtain bis(indolyl)methanes has been reported. The catalyst exhibited remarkable activity, recyclability, and tolerated a wide variety of functional groups providing the desired bis(indolyl)methanes in excellent yield (64–96%) at room temperature using ethanol as a solvent. The effect of different reaction parameters like solvent, temperature, catalyst doses, and recyclability were investigated for the title reaction.     

Spirodiketopiperazines of mannofuranose: carbopeptoid α-amino acid esters at the anomeric position of mannofuranose

Epimeric mannofuranose anomeric aminoesters are prepared from readily available azidolactones and can act as building blocks for the incorporation of mannofuranose units into peptide chains [carbopeptoids]; alternative acylating conditions allow either rapid acylation of the more stable but kinetically hindered amine or reaction with the less hindered but less stable amine to allow control of the anomeric configuration of the products. This is exemplified by coupling of the aminoesters with glycine derivatives to give dipeptide equivalents, and subsequent cyclization to spiro diketopiperazines. Anomers with the nitrogen function cis to the 2,3-diol are more stable than those with nitrogen trans; mannofuranose derivatives are more stable than the mannopyranose isomers.     

Structural variations of N-acetylneuraminic acid,part 19: Synthesis of both epimeric pairs of the 4-C-methyl- and 4-deoxy-4-C-methyl- as well as of the β-methylketoside of 4-deoxy-4-C-methylene-N-acetylneuraminic acid

Summary While the reaction of the 4-oxo-Neu 5 Ac derivative2 a with tributoxy methyl zirconate led exclusively to equatorial 4-C-methyl derivative3 a, the analogous reaction with tetramethyl zirconate yielded a 3:2 mixture of both diastereoisomeres3 a and4 a. After removal of protecting groups the 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid5 a and 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-talo-2-nonulosonic acid6 a were obtained. The 4-C-methylene derivative was prepared by treatment of the same 4-oxo-derivative with CH₂I₂/Zn/Cp ₂ZrCl₂. Subsequent hydrogenation led to both epimeric 4-deoxy-4-C-methyl derivatives8 a and9 a. Final removal of protecting groups gave the 5-acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid10 a respectively the 5-acetamido-2,7-anhydro-4-C-methyl-3,4,5-trideoxy-D-glycero-D-talo-2-nonulosonic acid11 a. The -methylketosides of the 4-deoxy-4-C-methyl- (16) and 4-C-methylene-Neu 5 Ac (15) were prepared via the peracetylated derivatives to obtain modell substrates for enzymatic studies. Thus all free acids were tested for inhibition of CMP-sialate synthease. Only the 4-C-methylene compound15 showed most unexpectedly a strong competitive inhibition of this enzyme.

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Strukturelle Abwandlungen an N-Acetylneuraminsäure, 19. Mitt.: Synthese der beiden Epimerenpaare der 4-C-Methyl- und 4-Deoxy-4-C-methyl- sowie des -Methylketosids der 4-Deoxy-4-C-methylen-N-acetylneuraminsäure. Verhalten gegenüber CMP-Sialat-Synthase

Zusammenfassung Während die Umsetzung des 4-Oxoderivates2 a mit (BuO)₃ MeZr ausschließlich zur equatorialen 4-C-Methylverbindung3 a führt, wurde bei der Reaktion mitMe ₄Zr ein 3:2-Gemisch der beiden Diastereomeren3 a und4 a erhalten. Das 4-C-Methylenderivat7 a wurde durch Reaktion derselben 4-Oxoverbindung mit CH₂I₂/Zn/Cp ₂ZrCl₂ erhalten. Eine anschließende Hydrierung (H₂-Pd/C) führte zu einem trennbaren Germisch der beiden 4-Deoxy-4-C-methylderivative8 a und9 a. Diese Verbindungen konnten durch das Entfernen der Schutzgruppen einerseits in die 5-Acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonsäure10 a und 5-Acetamido-2,7-anhydro-4-C-methyl-3,4,5-tridoxy-D-glycero-D-talo-2-nonulosonsäure11 a umgewandelt werden. Die Verbindungen Methyl-5-acetamido-4-C-methylen-3,4,5-trideoxy--D-manno-2-nonulopyranosidonat (15) und Methyl-5-acetemido-4-C-methyl-3,4,5-tridoxy--D-glycero-D-talo-2-nonulopyranosidonat (16) wurden als Modellverbindungen für enzymatische Untersuchungen über peracetylierte Zwischenstufen hergestellt. Überraschenderweise zeigte nur die 4-C-Methylenverbindung15 eine starke kompetitive Hemmung gegenüber CMP-Sialat-Synthase.