Synthesis of novel carboranyl derivatives of α-amino acids

New routes to closo-carboranyl derivatives of L-lysine and L-glutamic acid with free gA-NH2 groups were proposed.     

Synthesis of α-amino nitriles through Strecker reaction of aldimines and ketoimines by using nanocrystalline magnesium oxide

Strecker reactions of various aldimines as well as ketoimines with TMSCN proceeded smoothly under mild conditions to give the corresponding α-amino nitriles and α,α-disubstituted α-amino nitriles, respectively, in good to excellent yields in the presence of nanocrystalline magnesium oxide. The reaction proceeds through hypervalent silicate species by coordination to O²⁻/O⁻ (Lewis basic site) of nanocrystalline magnesium oxide, proved by ²⁹Si NMR.     

Synthesis and reactions of α-fluoro-α-amino amides

N-((S)-1-Phenylethyl)halofluoroethanamides have been investigated as precursors to N-protected α-fluoro-α-amino amides by nucleophilic displacement of halide with nitrogen nucleophiles such as potassium phthalimide, sodium succinimide, sodium glutarimide, trimethylamine and sodium azide. With single diastereoisomers of the iodofluoroethanamide, clean inversion of configuration occurs at room temperature, but subsequent epimerisation may occur as a result of the liberated iodide. The α-fluoro-α-amino amides made underwent a wide variety of reactions depending on conditions, but in many cases the carbon-fluorine bond was compromised. However, reacting trimethylamine and N-((S)-1-phenylethyl)iodofluoroethanamide gave the corresponding α-fluorobetaine amide, and subsequent acidic hydrolysis led to α-fluorobetaine as the first example of an ‘unprotected’ α-fluoroamino acid.     

Synthesis of unnatural N-glycosyl α-amino acids via Petasis reaction

A convenient and efficient protocol for the synthesis of unnatural N-glycosyl a-amino acids was developed.Condensation of 1,3,4,6-tetra-O-actyl-β-D-glucosamine hydrochloride,alkenyl boronic acid,and glyoxylic acid was achieved in CH_2C1_2 to give the derivatives of 2-(N-glycosyl)aminobut-3-enoic acid which may find applications in glycobiology research and medicinal chemistry.     

Synthesis ofN-(amidomethyl)- andN- (imidomethyl)-α-amino acid esters by reactions of α-amino acid esters with formaldehyde and amides or imides

Reactions of hydrochlorides of glycine, alanine, phenylalanine, L-isolcucinc, and L-valine esters with aromatic and heteroaromatic carboxamides afforded hydrochlorides of the correspondingN-(amidomethyl)--amino acid esters.N-(Phthalimidomethyl)--amino acid esters were obtained by reactions of -amino acid esters containing free amino groups with formaldehyde and phthalimide, The¹H NMR studies demonstrated that the chiral centers of -amino acids may be retained in the course of condensation. Reactions of the Mannish bases obtained and their hydrochlorides with acetic anhydride and tosyl chloride afforded the correspondingN-aryl andN-sulfonyl derivatives.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp, 1761–1769, July, 1996.     

Reaction of γ-dicarboxylic acids amides and imides with trifluoromethanesulfonamide and formaldehyde

Three-component condensation of trifluoromethanesulfonamide with paraformaldehyde and succinamide depending on the reaction conditions led alongside bis(trifluoromethanesulfonamido)methane to the formation of a substitution product, bis[(trifluoromethylsulfonyl)aminomethyl]succinamide, or to a cyclization product, N-[trifluoromethylsulfonyl)aminomethyl]succinimide. The attempt to obtain the latter by the reaction of the trifluoromethanesulfonamide sodium salt CF₃SO₂NHNa with N-chloromethylsuccinimide unexpectedly resulted in N,N-bis(succinimidomethyl)-trifluoromethanesulfonamide. Analogously the reaction of CF₃SO₂NHNa with N-chloromethyl-phthalimide gave N,N-bis(phthalimidomethyl)trifluoromethanesulfonamide. The reaction of CF₃SO₂NHNa with succinimide and phthalimide in water and alcohol solution resulted in the ring opening and further transformation of the formed monosubstituted N-(trifluoromethylsulfonyl)amides of succinic and phthalic acids.     

Synthesis and resolution of new paramagnetic α-amino acids

New, paramagnetic unnatural α-amino acids were synthesized by the O'Donnell method. In the new amino acids nitroxide is condensed with thiophene, benzene, and tetrahydroisoquinoline ring, or linked through a methylene, benzyl or propargyl spacer. Some of the racemic paramagnetic α-amino acid esters described earlier or in this work were resolved by fractional crystallization of diastereomeric salts. Another approach for optically active paramagnetic amino acids is the modification of S-tyrosine derivatives with Pd-catalyzed cross-coupling reactions with paramagnetic acetylene and with a paramagnetic boronic acid.     

Interactions between octyl-β-D-glucoside and α-amino acids or small peptides

The interactions between octyl--D-glucoside and glycine in water have been investigated by surface tension, viscosity, and density measurements. The results show that the -amino acid causes an unexpected lowering of the critical micellar concentration of octyl--D-glucoside. Such a finding has been interpreted in temss of dipole-dipole interactions between the hydrophilic site of the surfactant and the peptidic cosluttes. From three to seven amino acid molecules have been estimated to be coordinated with each glucoside unity in the micellar state. The research has been extended to glycine oligopeptides and L-lysine. The latter compound has effects similar to those observed with glycine whereas diglycine and triglycine show weaker effects on the micellization process.     

Synthesis of trialkylaluminum derivatives by the reaction of non-solvated aluminum hydride with α-olefins

Hydroalumination of -olefins by non-solvated polymeric aluminum hydride (AlH₃) _n occurs at 120—140 °C. Mechanochemical activation accelerates this reaction. The addition of catalytic amounts of the prepared R₃Al forms to the reaction system decreases the temperature of the process to 90—100 °C. The greatest initiation effect is observed when ate-complexes of the MAlR₄ type (M = Li, Na) are used: the reaction occurs with a higher rate already at 60—90 °C affording R₃Al free of admixtures of carbalumination products and dimers of -olefins.     

Synthesis and microbial transformation of β-amino nitriles

Rhodococcus equi A4, Rhodococcus erythropolis NCIMB 11540 and Rhodococcus sp. R312 were investigated towards their ability to produce β-amino amides and acids from β-amino nitriles. The microorganisms show comparable trends: five-membered alicyclic 2-amino nitriles were transformed significantly faster than the six-membered compounds and the products of trans-2-amino nitriles (amides and acids) were formed considerably faster than the cis-counterparts (amides). The trans-five membered nitriles gave the amides (1b, 5b) in excellent enantiomeric excess (94-99%), the biotransformation of trans-six membered substrates resulted in the formation of the acid (3c, 7c) in excellent ee (87-99%). The ee's of the cis-compounds were throughout lower. Fifteen new substances were synthesized and characterized in the course of this work.     

Synthesis of α-fluoro-β-amino acids via the Reformatsky reaction of chiral N-tert-butylsulfinylimines with ethyl bromofluoroacetate

Treatment of chiral N-tert-butyl sulfinylimines with ethyl bromofluoroacetate in the presence of activated Zn dust in THF afforded the α-fluoro- β-amino acid derivatives in good yields(70-86%) and moderate diastereoselectivity(66:34-92:8).     

Synthesis ofα-substitutedα-amino acids by the alkylation of 5-oxazolinone derivatives

Methods have been developed for the alkylation of 5-oxazolinone derivatives in DMF in the presence of K₂CO₃, KOH, or diisopropylethylamine and a phase transfer catalyst as well as for the preparation of-methyl-phenylalanine,-methylalanine,-methylalanine, and the methyl ester of N-benzoyl--methylalanine. Increasing the initial concentration of the starting 5-oxazolinone in the reaction mixture leads to a sharp drop in the yield of reaction products due to side condensation reactions. The reaction of 2-phenyl-4-benzyl-5- oxazolinone with ethyl iodide gave a dimer namely, 3-(benzoylamino)-3,5-dibenzylpyrrolidine-2,4-dione.Latvian Institute of Organic Chemistry, LV-1006 Riga. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 829–833, June, 1994. Original article submitted January 21, 1994.     

Coupling reaction between electron-rich pyrimidinones and α-amino acids promoted by phosphonium salts

Coupling reaction between electron-rich 2-morpholino-4(3H)-pyrimidinone and nucleophilic side chains of several natural α-amino acids promoted by phosphonium salt has been developed to prepare new optically active pyrimidin-4-yl amino acids. The best results were obtained using a two-step method through the easily available benzotriazolyl-1-oxy intermediate. A detailed optimization study of this reaction is discussed.     

Quantum-chemical modeling of the mechanism for reaction of arenesulfonyl chlorides with α-amino acids

We have calculated the potential energy surface for arenesulfonylation reactions of a-amino acids and glycine hydrates. We have shown that all the reactions occur via a complicated route, with varying angle of attack by the nucleophile according to an S _N2 mechanism. Hydration of glycine lowers the activation energy compared with the gas phase.     

Synthesis of pyridine derivatives by reactions of α,β-unsaturated nitriles with 2-oxo-cycloalkano carbothioic acid anilides

Summary The tandem Michael addition-cyclization of 2-oxo-cycloalkane carbothioic acid anilides1–3 to benzylidenemalononitrile4 yielded spiroannulated pyridines5–7. Reaction of acrylonitrile with2 and3 gave 2,2-disubstituted Michael adducts14,15, whereas with1 led to 2,2,5-tri(2-cyanoethyl)-cyclopentanone11.

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Synthese von Pyridinderivaten durch Reaktionen von ,-ungesättigten Nitrilen mit 2-Oxo-cycloalkano-thiokohlensäure-aniliden

Zusammenfassung Die Michael Tandem-Addition-Cyclisierung von 2-Oxo-cycloalkano-thiokohlensäure-aniliden1–3 mit Benzylidenmalononitril4 ergab die spiroannelierten Pyridine5–7. Reaktion von Acrylnitril mit2 und3 ergab die 2,2-disubstituierten Michael-Addukte14,15, wohingegen mit1 2,2,5-Tri(2-cyanethyl)-cyclopentanon11 erhalten wurde.