Asymmetric synthesis of beta-hydroxy amino acids via aldol reactions catalyzed by chiral ammonium salts

The Cinchona alkaloid derived chiral ammonium salt developed by Park and Jew functions as an effective catalyst for the synthesis of beta-hydroxy alpha-amino acids via asymmetric aldol reactions under homogeneous conditions. The syn diastereomers are obtained in good ee, and aryl-substituted aliphatic aldehydes are the best substrates for the reaction. These results represent the highest ee's obtained to date in direct aldol reactions of glycine equivalents catalyzed by inexpensive, readily prepared chiral ammonium salts.     

Allylic halogenation of unsaturated amino acids

A range of dehydro amino acid derivatives has been prepared and subjected to halogenation using either molecular bromine or chlorine, or NBS. Allylic halogenation of the unsaturated amino acid side chains occurs through radical bromination with NBS. The procedure is complementary to treatment with chlorine, which also affords allyl halides. This latter and unusual reaction is shown through a deuterium labelling study to proceed via an ionic mechanism. The choice of NBS or chlorine for allyl halide synthesis is shown to depend on the potential to avoid competing reactions, such as halolactonization of leucine derivatives with chlorine, and hydrogen abstraction and bromine incorporation at multiple sites on treatment of isoleucine derivatives with NBS. The synthetic utility of the allyl halides prepared in this study is indicated through the synthesis of a cyclopropyl amino acid derivative and the extension of the carbon skeleton of an amino acid side chain.     

Stevens rearrangement of unsaturated ammonium salts. Synthesis of substituted furans

Ammonium salts bearing but-2-ynyl and phenacyl or 2-(naphth-2-yl)-2-oxoethyl moieties at the nitrogen atom underwent Stevens rearrangement to form substituted furan-3-amines. Quaternization of the latter afforded appropriate iodomethylates.     

Synthesis of fulleropyrrolidines through the reaction of [60]fullerene with quaternary ammonium salts and amino acids

The reactions of [60]fullerene with amino acids and quaternary ammonium salts in toluene afforded two fulleropyrrolidine derivatives. One fulleropyrrolidine derivative contained a RCH moiety originating from quaternary ammonium salts through C–N bond cleavages and other fulleropyrrolidine derivatives contained a PhCH moiety originating from toluene through C–H bond cleavage. By using chlorobenzene instead of toluene as solvent, only one fulleropyrrolidine derivative containing a RCH moiety was obtained in the reactions.     

Heterocyclization of amino alcohols into saturated cyclic quaternary ammonium salts

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Formation of ammonium salts of 2-amino-3-formylbutanesulfinic acids in the reaction of 3-methyl-2,3-epoxysulfolane with amines

The reaction of 3-methyl-2,3-epoxysulfolane with amines proceeds with opening of not only the epoxide ring but also opening of the sulfolane ring to give the corresponding salts of 2-amino-3-formylbutanesulfinic acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1481–1483, November, 1985.     

Synthesis of the unsaturated diamines by the Stevens rearrangement of 4-diethylaminobutyn-2-yl-containing ammonium salts

Ammonium salts containing 4-diethylaminobutyn-2-yl and 2-alkenyl groups undergo the Stevens 3,2-rearrangement under the action of potassium hydroxide in anhydrous benzene to form the unsaturated diamines.     

Crystal packing of ammonium salts of arylenebis(phenylphosphinic) acids

It was shown for the first time that the crystal packing mode of the ammonium salt of thiophene-2,5-diylbis(phenylphosphinic acid) substantially differs from that of the dimethyl-ammonium salt of 1,4-phenylenebis(phenylphosphinic acid). The former crystal packing is a three-layer supramolecular sandwich structure consisting of two anionic layers separated by a layer of ammonium cations, whereas the supramolecular organization of the latter salt is based on alternating layers of anions and cations linked by hydrogen bonds.     

Formation of solid solutions of ammonium and cesium salts by explosion

Conclusions Solid solutions of NH₄Cl-CsCl and NH₄I-CsI were obtained by the explosion compression method. The theory was expressed that the synthesis of the solutions took place at the time of the action of the high pressure.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2323–2324, October, 1973.     

Comparative studies of the behavior of unsaturated acids and their salts in hydrogenation over platinum

Hydrogenation of unsaturated aliphqtic acids in water and of their unsaturated salts in aqueous metal hydroxide solutions over Pt black has been studied. Kinetic measurements are compared with quantum-chemical calculations.

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Pt-. .

     

New unsaturated amino acids containing an allylsilane moiety on the lateral chain

New enantiomerically enriched polyfunctionalized allylsilanes have been obtained from the synthetic elaboration of naturally occurring serine. In particular, an oxazolidine bearing an allylsilane framework on the lateral chain proved to be a suitable precursor for the corresponding silylated vinyl glycine derivatives.     

Synthesis of non-natural cyclic amino acids from available unsaturated tertiary amines

New approach is developed to the synthesis of cyclic amino acids derivatives. Unsaturated tertiary amines react with ethyl diazoacetate under the catalysis by copper catalyst Cu(F₃acac)₂ leading to the formation of products of [2,3]-sigmatropic rearrangement which via the metathesis of double bonds undergo a ring closure. The subsequent hydrogenation of compounds obtained furnished esters of 6- and 7-membered cyclic α-amino acids. Besides the racemic also optically active compounds were obtained, in particular, esters of (R)- and (S)-pipecolic acid.     

基于链状氨基酸N-手性季铵盐合成中的取代反应研究

手性季铵盐作为相转移催化剂(Phase-transfer catalysts ,PTC) 能使非均相反应在温和条件下进行,操作简单,反应速率加快,产率明显提高,因此这一技术在有机合成中具有广泛的应用.这些季铵盐主要是以金鸡钠生物碱衍生的[1,2],近年来出现了一些其它类型的季铵盐[3],但是它们的制备一般比较困难,大多数催化效果不是很理想;并且这些季铵盐的结构有一定局限,改造比较困难.同时这些季铵盐大都是 C-手性的,很少有N-手性的[4,5];在以前的不对称反应中,有意识地构建N-手性季铵盐及N-手性在不对称反应中的作用鲜有报道[6].     

Zwitterionic amino acids as precursors for nonmetal cation pentaborate salts

Nonmetal cation (NMC) pentaborate structures were synthesized using the amino acid molecules as cations precursors. Chemical composition analysis, infrared spectroscopy, mass analysis, boron nuclear magnetic resonance, and thermal gravimetric analysis (TGA/DTA) methods were used for structural characterization. The hydrogen storage efficiency of molecules was also determined experimentally. The recorded infrared spectra support the structural similarities of the molecules. Stretchings of pentaborate rings and characteristic peaks of amino acids were detected in infrared spectra. When the thermal analysis curves were recorded, it was found that the structures showed similar decomposition steps. Due to the result of thermal decay, glassy boron oxide (B₂O₃) formation was observed as the final decomposition products of all molecules. Peaks associated with boric acid, triborate, and pentaborate were observed in the ¹¹B spectra of these salts. Powder X-ray diffraction spectroscopy supports the presence of BO₃ and BO₄⁻ groups regarding the presence of pentaborate rings. It also indicates the high crystallinity of the structures. The molecular cavities detected by brunauer–emmett–teller analysis were found to be 3.586, 1.922, 1.673, and 1.923 g/cm³. Low-molecular cavities can be attributed to the high hydrogen-bonding capacity of the structures. The hydrogen capture efficiency of the pentaborate salts was found to be in the range of 0.039-0.     

The synthesis of quaternary ammonium salts from ammonium salts and dialkyl carbonate

Quaternary ammonium salts were synthesized from ammonium salts and dialkyl carbonates over an ionic liquid catalyst 1-ethyl-3-methylimidazolium bromide.