Synthesis of deuterium and tritium labelled phenyl glycine

A new method of synthesis of phenyl glycine labelled with deuterium and tritium was elaborated. Labelled phenyl glycine was obtained by isotope exchange method between phenyl glycine and deuterated or tritiated water at elevated temperature in hydrochloric acid medium using K₂PtCl₄ as a catalyst. 37 GBq /1 Ci/ HTO was used for the synthesis of tritiated phenyl glycine and labelled product with specific activity of 185 MBq/mole /5 mCi/mole/ was obtained.     

The fragmentations of substituted cinnamic acids after electron impact

The fragmentations of a number of cinnamic acids substituted at the phenyl ring have been studied with the aid of 70 eV mass spectra and mass analysed ion kinetic energy spectra. Evidence is presented that the formation of [C₉H₇O₂]⁺ ions occurs by intramolecular aromatic substitution reactions. A mechanism is proposed for the energetically favourable loss of the substituents from meta and para positions of the phenyl ring. The analytical use of intramolecular aromatic substitution reactions is briefly discussed.     

Study of exchange of hydrogen for deuterium and tritium in α-aminoalkylphosphonous acids

The kinetics of isotope exchange of hydrogen for deuterium in -aminoalkylphosphonous acids as a function of the pH were investigated by PMR spectroscopy. Tritiumlabeled -aminoalkylphosphonous acids were obtained as a result of direct hydrogen- tritium exchange between T₂O and hydrophosphoryl compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1966–1969, September, 1990.     

Preparation of substituted gem-dimethylcyclopropanecarboxylic acids

Conclusions A method, based on the addition of Grignard reagent to cyclopropene hydrocarbons, was proposed for the synthesis of alkyl-, phenyl-, and alkenylcyclopropanecarboxylic acids that bear a geminal dimethyl grouping in the ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 669–671, March, 1979.     

Mesogens with central naphthalene core substituted at various positions

We have prepared liquid crystalline materials based on hydroxynaphthalene carboxylic acids. The mutual location of both functional groups has been varied, which resulted in compounds possessing a bend angle of 120° and 60°, therefore in bent-core and V-shaped compounds, respectively. The mesomorphic properties have been established with polarizing optical microscopy, DSC measurements and X-ray investigation. The properties of the studied have been compared with analogous derivatives to establish the role of ester orientation in the vicinity of the central naphthalene core.     

Metal-free and base-free decarboxylation of substituted cinnamic acids in a deep eutectic solvent

Abstract

A metal-free and base-free strategy was developed in DES to synthesize styrenes for the first time by decarboxylation of cinnamic acid derivatives, which provided a renewable and cost efficiently protocol to access various styrenes including those with functional groups such as 4-vinylphenol and 1-chloro-4-vinylbenzene.     

Synthesis of tritium labelled monomers and polymers

The use of P₂O₅ for promoting the tritiation of various monomers and polymers has been investigated. Methyl methacrylate and vinyl acetate may be labelled at ambient temperatures by this procedure which is also applicable to labelling polystyrene and poly(α-methylstyrene). Exchange labelling of polymer substrates is most conveniently carried out in chlorinated hydrocarbons. The rate of tritium exchange increases with solvent polarity and temperature. Monomers of high radiochemical purity may be derived from the thermal depolymerization of tritiated polystyrene, poly(α-methylstyrene) and poly(methyl methacrylate).     

Asymmetric synthesis of l-proline regio- and stereoselectively labelled with deuterium

A synthesis of l-proline where all of the ring methylenes are stereoselectively labelled with deuterium is described. A catalytic deuteration of protected 3,4-dehydro-l-proline using transition metal catalyst followed by RuO₄-oxidation gave a [3,4-D₂]pyroglutamic acid derivative. A syn-selective deuteration of the aminal derived from the pyroglutamate with Et₃SiD–BF₃·OEt₂ furnished (2S,3S,4R,5S)-[3,4,5-D₃]proline. The present procedure is also applied to the synthesis of the corresponding (2S,3S,4R,5R)-isomer.     

Preparation and alkylation of substituted β-hydroxydithiocinnamic acids

A number of substituted β-hydroxydithiocinnamic acids have been prepared. By use of so-called ion-pair extraction technique a general method has been found for the preparation of β-hydroxydithiocinnamic esters in high yields. From these esters both symmetrical and unsymmetrical ketene mercaptals have been synthesized, and in some cases thio-Claisen rearrangement and subsequent ring-closure reactions have been observed.     

High temperature solid state catalytic isotope exchange with deuterium and tritium

A method for synthesizing tritium- or deuterium-labeled amino acids, peptides and biogenic amines through high temperature solid state catalytic isotope exchange (HSCIE) is proposed. The dependence of the degree of isotope exchange in HSCIE on the structure of the compound, the reactivity of hydrogen at different carbon atoms and the conditions of the process has been examined. If HSCIE is performed in the temperature range of 373 to 413K, the selectivity of isotopic label incorporation comes to 70% or higher. When the tritium label is introduced into peptides, they retain the configuration of asymmetric atoms, even upon the substitution of tritium for hydrogen at the -carbon atoms of the amino acid residues. HSCIE at 453–513K leads to an even distribution of the isotopic label over the organic compound molecule. The results of³H NMR spectroscopy highlighting the distribution of the tritium label in the organic compound molecules are presented. The configuration of asymmetric atoms in amino acids is preserved to a high extent upon 80–90% substitution of isotopes for hydrogen atoms.Presented at the 12th Radiochemical Conference, Marianské Lazné May 7–11, 1990.     

Preparation of l-serine and l-cystine stereospecifically labeled with deuterium at the β-position

The synthesis of l-serine and l-cystine stereospecifically labeled with deuterium at the β-position is described. The carboxyl group of d-serine was transformed into chirally deuterium-labeled alcohol via asymmetric reduction of 1-deuterio aldehyde, while the original hydroxymethyl group was converted into a carboxyl functionality to afford (2S,3R)-[3-²H]serine. Functional group interconversions of the hydroxyl group in the obtained deuterium-labeled l-serine gave (2R,2′R,3S,3′S)-[3,3′-²H₂]cystine.     

Methylation of the sulfolane ring at the 2 and 2, 5 positions

The possibility of alkylating sulfolane and its derivatives is investigated. A new method of introducing a methyl group at positions 2 and 2, 5 in the sulfolane ring, using sulfolanylmagnesium bromide is put forward.     

Synthesis of some 6-keto morphinan mu opiate receptor agonists labelled with tritium at high specific activity

The high specific activity tritiation of oxymorphone and pentamorphone is described.     

One-pot synthesis of cinnamic anhydrides from cinnamic acids and 6-chloro-2,4-dimethoxy-sec-triazine (CDMT) at room temperature

Symmetric cinnamic anhydrides were prepared by the reactions of cinnamic acid substrates with 6-chloro-2,4-dimethoxy-sec-triazine. The reactions were performed at room temperature for 15?h. Diverse cinnamic acid substrates bearing electron-withdrawing or -donating groups worked well, providing the corresponding cinnamic anhydrides in moderate-to-good yields     

Preparation of radioactive enantiomers of amino acids using labelled racemates only

It is shown from experiments on leucine, that is possible to obtain pure enantiomer tracers of amino acids by using radioactive racemates only. The resolution takes place in a single crystallization step after mixing the active racemate with the inactive enantiomer, due to an absolute stereoselection.