Novel approach to the synthesis of aliphatic and aromatic α-keto acids

A new practical and efficient synthesis of α-keto acids was accomplished starting from the synthon 1,4-diacetylpiperazine-2,5-dione. The synthesis encompasses both aromatic and aliphatic substrates proving to be versatile and innovative with excellent carbon economy and recycling of the glycine by-product.     

Silver-catalyzed decarboxylative cross-coupling of α-keto acids with alkenes giving approach to chalcones

A silver-catalyzed decarboxylative cross-coupling of α-keto acids with alkenes is reported. The method, with a wide range of substrate tolerance and mild operational conditions, can produce various chalcone derivatives in moderate to high yields from easily available starting materials.     

An organocatalytic approach to enantiomerically enriched α-arylcyclohexenones and cyclohexanones

The presence of a p-nitrophenyl group converts acetone into an excellent and versatile nucleophile in organocatalytic processes, able to react with α,β-unsaturated aldehydes affording β-substituted α-arylcyclohexenones via a Michael reaction/aldol reaction/dehydration sequence, which occurs in good yields, ee up to 96% and complete diastereoselectivity. The resulting compounds are excellent synthons for the diastereoselective preparation of a variety of synthetically useful polysubstituted cyclohexanones and derivatives.     

A novel approach to α-keto acid derivatives via palladium-catalyzed arylation and vinylation of methyl α-methoxyacrylate

Methyl α-methoxyacrylate reacts stereoselectively with aryl iodides and vinyl triflates under palladium catalysis to give enol ethers of arylpyruvates and of β,γ-unsaturated α-keto esters in good to moderate yields.     

An efficient synthesis of substituted alkyl acrylates using α-keto amides

The addition of α-keto amides as a NH-acid to alkyl propiolates and dialkyl acetylenedicarboxylates in the presence of a catalytic amount of triphenylphosphine gives the corresponding substituted alkyl acrylates.     

An approach to eriolanin. Synthesis of α-methylene lactones of trans-1,3-dihydroxycyclohexanes

A new synthesis of α-methylene lactones is discussed which incorporates an intramolecular epoxide opening with a vinyl anion.     

Additions of free dimethylgermylene to vinyl ketones and α-diketones

Derivatives of 1-oxa-2-germacyclopent-4-ene are obtained from germylenes with a number of cyclic or acyclic vinyl ketones, and 1,3-dioxa-2-germacyclopent-4-enes with different non-enolizable α-diketones. Structure-mechanism relationships are discussed.     

An approach to the synthesis of α-l-fucopyranosyl phosphoric mono- and diesters via phosphite intermediates

The reagent chloro-β-cyanoethyl-N,N-diisopropylamino-phosphoramidite reacts smoothly with the anomeric hydroxyl group of a properly protected (benzyl) α-L-fucopyranose to afford a relatively stable phosphite intermediate in high yield. The latter can easily be converted into valuable α-L-fucopyranosyl phosphoric mono- and diesters.     

Click-chemistry approach to isoxazole-containing α-CF3-substituted α-aminocarboxylates and α-aminophosphonates

A convenient strategy for the synthesis of isoxazole-containing α-CF(3)-substituted α-aminocarboxylates and α-aminophosphonates have been developed. The method is based on copper-catalyzed 1,3-dipolar cycloaddition of different aromatic nitrile oxides to functionalized acetylenes.     

Silylene transfer to α-keto esters and application to the synthesis of γ-lactones

Disubstituted α-hydroxy acids have been synthesized by metal-catalyzed silylene transfer to α-keto esters. A range of substituents are tolerated in the transformation with the exception of branched groups at the vinylic position. The α-hydroxy acid products can be converted into γ-lactones using a variety of lactonization conditions.     

An Ireland-Claisen rearrangement approach to β-amino acids

The first use of enamide substrates in an Ireland-Claisen [3,3]-sigmatropic rearrangement reaction is presented as a novel route to complex β^2,3-amino acids     

Reaction of adenine with an α-chlorooxetane: An approach to the synthesis of oxetane nucleosides

The reaction of adenine with 3,5-anhydro-5R-chloro-1,2-O- isopropylidenexylofuranose, a stable α-chlorooxetane, gives a mixture of the two epimers of 5-[9-adenyl]-3,5-anhydro- 1,2-O-isopropylidenexylofuranose; the structure of 5R-[9- adenyl)-3,5-anhydro-1,2-O-isopropylidenexylofuranose was established by X-ray crystallography.     

A new approach to the synthesis of α-chlorocycloalkanones

α-Chlorocycloalkanones(Ⅳ) were synthesized from cycloalkanones via potassiumα-oxocycloalkylsulfonates(Ⅱ).A two-step mechanism was proposed to explain the formation ofⅣfromⅡ.     

Divergent synthetic approach to 6'-modified α-GalCer analogues

A synthetic approach is presented for the synthesis of galacturonic acid and D-fucosyl modified KRN7000. The approach allows for late-stage functionalisation of both the sugar 6'-OH and the sphingosine amino groups, which enables convenient synthesis of promising 6'-modified KRN7000 analogues.     

An approach to the synthesis of 1,2λ-azaphosphinines

A novel approach to 1,2λ⁵-azaphosphinines has been elaborated. Aminophosphonium chlorides bearing a β-dialkylaminocrotonic nitrile residue react with N,N-dimethylformamide dimethylacetal to afford 1,2λ⁵-azaphosphinines.     

An easy approach to α,β-unsaturated δ-thiolactams via a RCM and thionation one-pot procedure

An easy approach to mono- and bicyclic derivatives of 5,6-dihydro-1H-pyridine-2-thione via a one-pot ring closing metathesis (RCM) of dialkenoic amides and thionation using Lawesson’s reagent, followed by isomerization of the 3,6-dihydro-isomer (if necessary), is described. The appreciable differences in the reactivity of diallylic amides in RCM reactions are discussed.     

Beyond the chiral pool: a general approach to β-amino-α-keto amides

A simple route was developed for the synthesis of optically enriched β-amino-α-keto amides. The highly diastereoselective addition of alkyl dithiolanecarboxylates to optically enriched sulfinimines affords the corresponding β-amino-α-keto esters in which the ketone carbonyl group is protected as a dithiolane. Amidation of the ester functionality with a primary amine proceeds readily at room temperature. Treatment with HCl cleaves the N-S bond of the sulfinyl group to provide a free amine functionality, which can then be incorporated into a peptide. Removal of the dithiolane protecting group under oxidative conditions proceeds without epimerization as exemplified by a model dipeptide.     

Palladium-catalyzed oxidative rearrangement of diaryl alkenyl carbinols to β,β-diaryl α,β-unsaturated ketones

An unusual oxidative palladium-catalyzed rearrangement of diaryl alkenyl carbinols to β,β-diaryl α,β-unsaturated ketones is described. The geometry of the alkene product is not determined by the electronic nature of the aryl substitutents but rather is determined by substitution pattern on the aryl rings. The reaction proceeds in good yields, utilizes oxygen at atmospheric pressure as the terminal oxidant, and tolerates a variety of functional groups on the aryl rings.