New β-amino-α-trifluoromethyl alcohols and their exploration in the synthesis of trifluoromethylated imidazole derivatives

Racemic and enantiomerically pure β-amino-α-trifluoromethyl alcohols were obtained via sequential nucleophilic trifluoromethylation of selected α-imino ketones, derived from arylglyoxals, and subsequent removal of the MeO or Ph(Me)CH substituent, respectively, located at the N-atom. The obtained products, containing a primary amino group, were used for the synthesis of imidazole N-oxides bearing a trifluoromethyl group as a part of the N(1)-alkyl chain. Imidazole N-oxides with an electron-withdrawing ester group at C(4) underwent spontaneous isomerization under the reaction conditions, and the corresponding imidazol-2-ones derivatives were isolated as final products.     

Syntheses with heterocyclic β-enaminonitriles: An expeditious synthetic approach to polyfunctionally substituted 5-phenylsulfonylthiophenes and their fused derivatives

Summary Phenylsulfonylacetophenones1 react with a mixture of elemental sulfur and malononitrile to yield the corresponding 2-amino-4-aryl-5-phenylsulfonylthiophene-3-carbonitriles2. Compound2a could be annelated to the corresponding thieno[2,3-d]pyrimidine and thieno[2,3-c]-pyrazole derivatives3 and5 upon reaction with nitrogen nucleophiles (cyanamide and hydroxylamine hydrochloride), respectively. The applicability and synthetic potency of5 to develop a facile convenient route to the polyfunctionally substituted thieno[2,3:3,4]pyrazolo[1,5-a]pyrimidines8, 14, 17, 20, and21 is reported. Chemical and spectroscopic evidences for the structures of the new compounds are presented.

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Synthesen mit heterocyclischen -Enaminonitrilen: Ein rascher synthetischer Zugang zu polyfunktionell substituierten 5-Phenylsulfonylthiophenen und ihren kondensierten Derivaten

Zusammenfassung Die Phenylsulfonylacetophenone1 reagieren mit einem Gemisch aus elementarem Schwefel und Malonsäurenitril zu den entsprechenden 2-Amino-4-aryl-5-phenylsulfonylthiophen-3-carbonitrilen2. Durch Umsetzung mit Stickstoffnucleophilen wie Cyanamid und Hydroxylaminhydrochlorid konnten aus Verbindung2a die entsprechenden Thieno[2,3-d]pyrimidin- und Thieno[2,3-c]pyrazolderivate erhalten werden. Das synthetische Potential und die Anwendbarkeit von5 zur Synthese polyfunktionell substituierter Thieno[2,3:3,4]pyrazolo[1,5-a]pyrimidine (8,14,17,20,21) werden beschrieben. Die Strukturen der neuen Verbindungen wurden durch chemische und spektroskopische Methoden abgesichert.

     

Facile access to α,β-dehydroalanine and α,β-dehydroamino butyric acid derivatives from DL-serines and threonines

Not only α,β-dehydroamino acids are important constituents for a number of bioactive peptides in nature, but also they are important building blocks for a variety of synthetic amino acids in organic synthesis. Methods to prepare dehydroamino acids have been reported extensively in the literature; however, efficient and convenient protocols are still required. Here we have developed a convenient method to prepare dehydroalanine (ΔAla) and dehydroamino butyric acid (ΔAbu) derivatives derived from DL-serines and DL-threonines, respectively. 4-Toluenesulfonyl chloride (TsCl) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were employed in this procedure, which carried out activation of hydroxyl group and β-elimination in one pot. Because it is convenient and easy to handle, this method will attract the attention of synthetic chemists.     

Synthesis of ethyl α-nitro-β-trifluoromethyl acrylate and β-trifluoromethyl-substituted tryptophan analogs and their plant growth regulating activity

Russian Chemical Bulletin - Ethyl α-nitro-β-trifluoromethyl acrylate was synthesized by nucleophile-catalyzed reaction of ethyl nitroacetate with excess trifluoroacetaldehyde methyl...     

Efficient synthesis of β-halogeno protected l-alanines and their β-phosphonium derivatives

Ring opening of oxazolines, prepared from l-serinates, with trimethylsilyl halides (TMSX) led to β-halogeno-N-benzoyl-α-amino esters in good to excellent yields. Quaternization of triphenylphosphine by the β-bromo or -iodo amino esters gave the corresponding β-phosphonium salts in overall yields of up to 93% and with e.e. >96%. Hydrolysis of the ester function afforded the phosphonium salt bearing an N-benzoyl-α-amino acid substituent, with partial racemization. However, the reaction of the TMSX with the carboxylic salt, prepared by saponification of the starting oxazoline ester, furnished the corresponding β-halogeno-N-benzoyl-α-amino acids in 70–95% yields. Quaternization of triphenylphosphine by the bromo or iodo derivatives led to the phosphonium salts bearing a free acid function in 95% yield, without racemization. The efficiency of this synthesis was demonstrated by the preparation of these phosphonium salts in excellent overall yields, by a one-pot procedure starting from the oxazoline.     

Stereoselective synthesis of α-hydroxy-β-amino acid derivatives from β-hydroxy-γ,δ-unsaturated sulfilimine

The first report on the use of N-sulfinyl benzylcarbamate for the preparation of N-Cbz sulfilimine from the corresponding sulfoxide is reported. The sulfilimine moiety is utilized as an intramolecular nucleophile for the regio- and stereoselective heterofunctionalization of an alkene to furnish a bromo carbamate which is used as a key advanced intermediate in the synthesis of representative α-hydroxy-β-amino acid derivatives.     

Convenient synthesis of mono- and di-β-hydroxy-β-bis(trifluoromethyl)-(di)imines from β-hydroxy-β-bis(trifluoromethyl)-ketones and (di)amines

A series of novel β-hydroxy-β-bis(trifluoromethyl)-imines (2a-j) and di(β-hydroxy-β-bis(trifluoromethyl))-diimines (3a-f) were prepared in moderate to good yields via a simple two-step approach: first, β-hydroxy-β-bis(trifluoromethyl)-ketones (1a-c) were obtained by a catalyst-free aldol reaction between liquid hexafluoroacetone sesquihydrate and ketones (acetone, acetophenone, and pinacolone, respectively); then, condensation of the latter fluorinated β-ketols 1a-c with primary amines or diamines was achieved in the presence of Lewis (montmorillonite, InBr₃, La(OTf)₃) or Brönsted (PTSA) acid catalysts. The molecular structures of mono- and di-β-hydroxy-β-bis(trifluoromethyl)-(di)imines 2e,h and 3a,f were determined and found to exhibit strong intramolecular (R)N?H-O hydrogen bonding.     

Short and efficient synthetic route to methyl α-trioxacarcinoside B and anomerically activated derivatives

A 9-step synthetic route to the complex carbohydrate methyl α-trioxacarcinoside B from 2-acetylfuran is described. Anomerically activated forms, including 1-phenylthio, 1-O-(4'-pentenyl), 1-fluoro, and 1-O-acetyl derivatives are also prepared.     

A new stereoselective approach to β-hydroxy-α-aminoacids and dipeptides

The chiral synthons 1, 2 and 1′ were submitted to aldol condensation to achieve both β-hydroxy-α-aminoacids and dipeptides. The configuration of the new stereogenic centers was assigned on the basis of ¹H NMR spectroscopic data.     

Acetyl- and O-alkyl- derivatives of β-mangostin from Garcinia mangostana and their anti-inflammatory activities

Pure β-mangostin (1) was isolated from the stem bark of Garcinia mangostana L. One monoacetate (2) and five O-alkylated β-mangostin derivatives (3–7) were synthesised from β-mangostin. The structures of these compounds were elucidated and determined using spectroscopic techniques such as 1D NMR and MS. The cytotoxicities and anti-inflammatory activities of these five compounds against RAW cell 264.7 were tested. The structural-activity relationship studies indicated that β-mangostin showed a significant activity against the LPS-induced RAW cell 264.7, while the acetyl- as well as the O-alkyl- β-mangostin derivatives did not give good activity. Naturally occurring β-mangostin demonstrated comparatively better anti-inflammatory activity than its synthetic counterparts.     

New approaches to β-trifluoromethylated enone derivatives

β-Trifluoromethylated enaminones 1 were prepared stereospecifically or high stercoselectively in 31-92% yields from the reaction of Weinreb amides with trifluoropropynyl lithium, followed by quenching with H₂O in the presence of amine derivatives. β-Trifluoromethylated enaminone 1a was reacted with aryl or alkynyl Grignard reagents to give Michael addition products 5 at 0 °C, whereas addition-elimination adducts, β-aryl (or alkynyl)-β-trifluoromethylated enones 6, were obtained stereospecifically in 50-92% yields after stirring at room temperature for several hours.     

Syntheses of quinolines and their derivatives from α,β-unsaturated aldehydes

Chemistry of Heterocyclic Compounds - The methods for the synthesis of quinoline and its hydrogenated derivatives from α,β-unsaturated aldehydes have been summarized for the first time....     

Synthesis of α-trifluoromethyl-phenethylamines from α-trifluoromethyl β-aryl enamines and β-chloro-β-(trifluoromethyl)styrenes

A novel synthetic approach towards α-trifluoromethyl-phenethylamines was elaborated by reduction of the electron deficient β-aryl-α-trifluoromethyl enamines and imines with sodium cyanoborohydride in the presence of trifluoroacetic acid. The starting imines were prepared by the reaction of primary amines with β-aryl-α-trifluoromethyl enamines or β-chloro-β-(trifluoromethyl)styrenes.     

Synthesis of new β-trifluoromethyl containing GABA and β-fluoromethyl containing N-benzylpyrrolidinones

A whole series of 3-(mono-, di-, trifluoro)methyl-substituted N-benzylpyrrolidinones 5a-c was synthesized by deoxyfluorination of corresponding 3-functionalized N-benzylpyrrolidinones. New β-trifluoromethyl containing GABA 4a was obtained in two alternative ways: by successive hydrolysis and hydrogenolysis of 3-trifluoromethyl N-benzylpyrrolidinone 5a and from trifluoroacetone as starting compound.     

Aminomethylation of chiral silyl enol ethers: access to β-homotryptophane and β-homolysine derivatives

We describe here the aminomethylation of chiral silyl enol ether derivatives using iminium ion. The choice of judicious precursors with adequate protecting groups for the silylation/aminomethylation step was required to achieve the synthesis of β²-homotryptophane in few steps. The same methodology was used to prepare a β²-homolysine derivative.     

Synthesis and structure of the β-carboline derivatives and their binding intensity with cyclin-dependent kinase 2

Series of 3-substituted of 6-aminosulfonyl-β-carbolines were designed and synthesized. In addition, the binding mode of these β-carboline derivatives with cyclin-dependent kinase 2 (CDK2) was studied by means of fluorescence measurements and molecular docking calculation. The results showed that replacement of 3-cyclohexylmethoxy group will increase the hydrophobic binding interaction with the deep hydrophobic pocket of CDK2 correlate to the higher binding intensity.     

Facile and Efficient One-Pot Synthesis of β-Carbolines

Initial formation of tetrahydrocarboline 3 from tryptophan methyl ester 1 and aldehyde 2 by Pictet–Spengler reaction, followed by treatment with trichlorocyanuric acid, provides a facile and efficient route for a one-pot synthesis of β-carbolines with excellent yields.     

Facile synthesis of novel α-methylene-pyrazole-carboxylate substituted imines and trans-β-lactams: Versatile synthons for diverse heterocyclic molecules

A simple, facile, and high yielding stereoselective approach for the integration of α-methylene-pyrazole-carboxylates at the β-lactam nucleus is described. These monocyclic β-lactams have been synthesized by treatment of 2-phenoxy/benzylthio/phenylthio ethanoic acids or acetoxyacetyl chloride/phthalimidoacetyl chloride 5a–e with novel α-methylene-pyrazole-carboxylate imines 4a–c using Et₃N and POCl₃ in refluxing toluene. All of the newly synthesized α-methylene-pyrazole carboxylate imines 4a–c and their β-lactam derivatives 6a–h have been fully characterized by spectroscopic techniques such as FTIR, NMR (¹H, ¹³C, and ¹³C DEPT-135), 2D-NMR (COSY and HSQC), and elemental analyses (CHN). The cycloaddition reaction was found to be highly stereoselective leading to the exclusive formation of trans-β-lactams 6a–h and trans configuration was assigned with respect to coupling constant values of C3-H and C4-H. The novel β-lactams 6a–h bearing α-methylene-pyrazole-carboxylate ring system will serve as useful synthons for highly functionalized acids, acetohydrazides/pyrazolones, alcohols, pyrazole carboxamides, peptides, and promising biologically active agents.     

A flexible synthetic route to isoxazolidine β-proline analogs

The function and higher order structure of β-proline oligomers have been relatively unexplored compared to other foldamer classes due in part to synthetic challenges associated with substituted monomers. Here we report a flexible synthesis of di- and trisubstituted isoxazolidine β-proline monomers that enables access to a wide range of densely functionalized analogs suitably protected for solid-phase synthetic protocols. This strategy utilizes chiral isoxazolines as key intermediates and can readily provide single stereoisomers of the target molecules.