Preparation of α-alkyl-β-amino acids via β-alanine Ni(II) complex

A new β-amino acrylic acid Ni(II) complex has been developed and used for the synthesis of α-alkyl-β-amino acids via alkylation with alkyl halides under operationally convenient conditions. The pivotal α-alkylated intermediate can be converted into the corresponding α-alkyl-β-amino acids via two steps with a wide range of substituents.     

Preparation of β-fluoro- and β,β-difluoro-histidinols

Nucleophilic attack of azide on 2-bromo-3-fluoro-3-(1-trityl-1H-imidazol-4-yl)-propan-1-ol (1a) in aprotic solvent occurs on the 2-position to give the 2-azido derivative (2a). Reduction of azide and removal of the trityl group produces β-fluorohistidinol (6a). Elimination of HBr from 1a followed by “FBr” addition to the resulting double bond gives 2-bromo-3,3-difluoro-3-(1-trityl-1H-imidazol-4-yl)-propan-1-ol (1b). Nucleophilic attack of azide followed by reduction and removal of the trityl group, as for the preparation of 6a, gives β,β-difluorohistidinol (6b). Initial attempts, under a variety of conditions, to oxidize the fluorinated histidinol precursors to carboxylic acids have not been successful.     

New approach to exclusive formation of both enantiomers of β-amino acid derivatives

A highly selective two-step approach to chiral β-amino esters via the hydride reductive amination of chiral allenes is reported. β-Enamino esters were obtained from the nucleophilic addition of amines to 2,3-allenoates bearing a chiral auxiliary. The reduction of the (1R)-(−)-10-phenylsulfonylisobornyl β-enamino esters gave the corresponding β-amino esters with S configuration whereas the reduction of the (1S)-(+)-10-phenylsulfonylisobornyl β-enamino esters led to β-amino esters with R configuration. The rationalization of the observed selectivity was supported by semi-empirical molecular orbital calculations (PM3).     

Enantioselective synthesis of β-amino acids. Part 10: Preparation of novel α,α- and β,β-disubstituted β-amino acids from (S)-asparagine

Perhydropyrimidinone (S)-1 is alkylated with very high diastereoselectivity to give trans products (2S,5R)-3, (2S,5R)–4 and (2S,5R)-5. Dialkylation of (S)-1 also proceeds with complete stereoselectivity to afford adducts (2S,5R)-6, (2S,5S)-6, (2S,5R)-7 and (2S,5S)-7. Hydrolysis (6N HCl, 100°C) of monoalkylated derivative (2S,5R)-3 gives enantiopure α-substituted β-amino acid (R)-8. Hydrolysis of dialkylated adducts 6 and 7 affords enantiopure α,α-disubstituted β-amino acids (R)- or (S)-9 and (R)- or (S)-10. Related iminoester (2S,6S)-2 is alkylated with complete diastereoselectivity to give products (2S,6S)-11–13 whose hydrolysis under relatively mild conditions (2N CF₃CO₂H, CH₃OH, 100°C) affords enantiopure N-benzoylated β,β-disubstituted β-amino acid esters (S)-14–16, with intact double bonds in the olefinic substituents.     

(S)-(−)-α-Methylbenzylamine as an efficient chiral auxiliary in enantiodivergent synthesis of both enantiomers of N-acetylcalycotomine

(S)-(−)-α-Methylbenzylamine 2 was used as a chiral auxiliary in the enantiodivergent synthesis of simple isoquinoline alkaloids. The prochiral imine moiety in compound 4 was reduced with different reagents, giving diastereomeric amines 5a or 5b, which subsequently were transformed to either (S)-(−)-N-acetylcalycotomine 6 or (R)-(+)-N-acetylcalycotomine ent-6 in good enantiomeric excess. ¹⁹F NMR of its Mosher's acid ester was used to establish the purities of final compounds.     

Z-Selective Preparation of β-Monosubstituted α,β-Unsaturated Amides Using Diphenylphosphonoacetamides

The Horner-Wadsworth-Emmons reaction of diphenylphosphonoacetamides [(PhO) 2 P(O)CH 2 CONRR'] ( 2a : R, R' = CH 2 Ph; 2b : R = CH 2 Ph, R' = H; 2c : R = Me, R' = OMe) was examined. The reaction of 2a was found to be Z -selective for benzaldehyde with selectivities up to 94:6. Reagent 2b led to reasonable selectivity for both benzaldehyde (85:15) and 3-phenylpropionaldehyde (87:13), while 2c was somewhat effective only for the latter aldehyde (83:17).     

Novel efficient synthesis of β-fluoro-β-(trifluoromethyl)styrenes

CF₃CFBr₂ was employed in catalytic olefination reactions of aromatic aldehydes. In situ prepared hydrazones of aldehydes were transformed to β-fluoro-β-(trifluoromethyl)styrenes by reaction with CF₃CFBr₂ under CuCl catalysis. Based on this reaction, a novel stereoselective approach towards β-fluoro-β-(trifluoromethyl)styrenes was elaborated. Nucleophilic vinylic substitution of fluorine by secondary amines, thiolates and alkoxides in β-fluoro-β-(trifluoromethyl)styrenes was also tested.     

Crystal structures of layered zirconium pentafluorides of methylammonium,glycinium, and β-alanine

For the first time, new hybrid organic-inorganic layered zirconium pentafluorides of methylammonium, glycinium, and β-alanine with the composition (CH₃NH₃)ZrF₅·0.5H₂O, (H₃NCH₂COOH)ZrF₅·2H₂O, and (H₃N(CH₂)₂COOH)ZrF₅ are synthesized and their structures are analyzed. In the studied compounds, CN of the Zr atom is 8, and its coordination polyhedron represents a dodecahedron sharing its 6 vertex with three neighboring Zr polyhedra. The Zr dodecahedra are joined with each other in planar netlike anion layers of the composition _∞²[ZrF₅]⁻. The anion layers are hydrogen bonded into a three-dimensional structure by H₂O cations and molecules.     

Stereoselective synthesis of unsymmetrical β,β-diarylacrylates by a Heck-Matsuda reaction: versatile building blocks for asymmetric synthesis of β,β-diphenylpropanoates, 3-aryl-indole, and 4-aryl-3,4-dihydro-quinolin-2-one and formal synthesis of (-)-indatraline

β,β-Disubstituted α,β-unsaturated esters may serve as valuable derivatives for the preparation of other highly functionalized systems found in many natural products and marketed drugs. The stereoselective synthesis of unsymmetrical β,β-diarylacrylate compounds possessing two similar aromatic groups remains a substantial challenge. A simple and convenient stereoselective protocol for the preparation of β,β-disubstituted acrylates via a Heck-Matsuda reaction is reported. Good to high yields were accomplished by a "ligand-free" Pd-catalyzed arylation reaction of cinnamate esters with arenediazonium tetrafluoroborates. Both electron-deficient and electron-rich arenediazonium salts could be employed as arylating reagents, and cinnamate esters were generally more reactive when substituted with an electron-donating group. The overall methodology is highly stereoselective, and this attribute was taken advantage of in the asymmetric Cu-catalyzed 1,4 reduction reaction to provide β,β-diarylpropanoates in high enantioselectivities. The synthesis of a 3-aryl indole and a chiral 4-aryl-2-quinolone from β,β-diarylacrylates was achieved by cyclization in the presence of a diphosphine ligated CuH catalyst. A convenient route for the asymmetric formal synthesis of the psychoactive compound (-)-Indatraline is also presented.     

Photochemical addition of diethyl ether to β,β,β',β'-tetrakis(trifluoromethyl)divinyl ether

The 1:1 adducts of diethyl and ,,','-tetrakis(trifluoromethyl)divinyl ether (1),i.e., 3,5-(ee)-bis[2,2,2-trifluoro-1-(trifluoromethyl)ethyl]-2,6-dimethyl-1,4-dioxane (2) (3 isomers) and 4-ethoxy-1,1,1-trifluoro-2-trifluoromethyl-3-[3,3,3-trifluoro-2(trifluoromethyl)propenyloxy]pentane (3), have been obtained by UV-irradiation of a solution of divinyl ether1 in diethyl ether. The X-ray structural investigation of the all-(e)-isomer of dioxane (2) has been carried out.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 85–88, January, 1994.     

Stability of New Zinc Complexes with β,βʹ-(Ethylenediamine)-N,N-dipropionic Acid

Russian Journal of General Chemistry - Stability constants of new zinc complexes with β,β?-(ethylenediamine)-N,N-dipropionic acid:...     

Preparation of β-Silyl-α,β-unsaturated Esters and 3-Silyl Allyl Alcohols

Acylsilanes react with lithium α-silyl ester enolates to provide β-silyl-α,β-unsaturated esters having predominantly the (Z) geometry. These esters were reacted with Grignard reagents and with lithium aluminum hydride to give the corresponding (Z) 3-silyl allyl alcohols.     

Enzymatic ammonolysis of ethyl (±)-4-chloro-3-hydroxybutanoate. Chemoenzymatic syntheses of both enantiomers of pyrrolidin-3-ol and 5-(chloromethyl)-1,3-oxazolidin-2-one

Lipase B from Candida antarctica efficiently catalysed the kinetic resolution of ethyl (±)-4-chloro-3-hydroxybutanoate through an ammonolysis reaction. Using this methodology, both enantiomers of 4-chloro-3-hydroxybutanamide were prepared and converted into pyrrolidin-3-ol and 5-(chloromethyl)-1,3-oxazolidin-2-one by simple processes consisting of a reduction reaction and a Hofmann rearrangement, respectively.     

Preparation of β-Seleno-α,β-Unsaturated Nitroalkenes Via A Sulfur-Selenium Exchange Reaction

Several β-seleno-α,β-unsaturated nitroalkenes were prepared via an addition-elimination process using the corresponding sulfinyl compounds and phenyl or methyl selenol.     

Spectrophotometric Studies on the Inclusion Formation of β-Cyclodextrin with 3,4-(Methylenedioxyphenyl) Benzylideneaniline

Complexation of -cyclodextrin with 3,4-(methylenedioxyphenyl) benzylideneaniline has been studied in aqueous solution by means of spectrophotometry. It was observed that the complexation attains equilibrium very slowly. The equilibrium constant of the 1:1 complexation between -CD and MDBA was determined, and its dependence on temperature examined. Findings are discussed in light of host–guest intermolecular interactions. Two possible mechanisms of complexation are proposed.     

β, β-Bis(trifluoromethyl)glycidic ester

Conclusions ,-Bis(trifluoromethyl)glycidic ester is far more active than ,-dimethylglycidic ester and is opened by amines on the side of the -carbon atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8 pp. 1529–1530, August, 1964     

Amino acids as cations: Tetrachlorocuprates (II) of glycine and β-alanine cations

The effect of glycine and β-alanine, when act as counterions, on the coordination geometry of the tetrachlorocuprates has been investigated.     

Asymmetric synthesis of β-monosubstituted and β,β-disubstituted N-(p-toluenesulfinyl)-α-(aminoalkyl)acrylates via anionic additions of (α-carbalkoxyvinyl)cuprates to thiooxime S-oxides

A series of new Baylis–Hillman adducts, β-monosubstituted and β,β-disubstituted N-(p-toluenesulfinyl)-α-(aminoalkyl)acrylates has been synthesized via asymmetric nucleophilic additions of (α-carbalkoxyvinyl)cuprates to chiral p-toluenesulfinimines. Modest to good yields (52.0–72.0%) and excellent diastereoselectivity (>90% de) have been obtained. The Z/E selectivity was found to be effected by solvents or cosolvents.