Diene condensation on zeolites, II. Influence of the zeolite structure and the nature of substituting cation on the reaction of alloocimene with α-methacrolein

The interaction of alloocimene with α-methacrolein on β-zeolite with various substituent cations (Fe, Ni, Zn, Cu and La) as well as on ZSM-5, erionite and mordenite has been studied at room temperature in dichloromethane. Substituent cations in β-zeolite as well as the silica/alumina ratio and alkali metal content in the zeolite structure were found to affect the formation of ocinal diastereomers. Therefore, we assume that a complex of active sites participates in the diene condensation: Alkali metals present in the zeolite suppress the (3+2)-cycloaddition reaction.     

Interaction of polynitro compounds with difluoroamine

Difluoroamine does not react with tetranitromethane and fluoro-, chloro-, and bromotrinitromethanes in DMF and in acidic media (CF₃COOH, ClSO₃H, FSO₃H, and oleum), but reacts with α-fluoro- and α-(difluoroamino)-α,α-dinitrotoluenes to give substitution products of the difluoroamino group for both the nitro groups,viz., PhC(NF₂)₂F and PhC(NF₂)₃, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1647–1649, August, 1998.     

Concerning the Solvent Effect in the Aldol Condensation

Summary.  Except for the catalyst and the temperature, the nature of the solvent also affects the aldol condensation, favouring α,β-unsaturated carbonyl compounds in alcoholic solvents or β-hydroxyl carbonyl compounds in tetrahydrofuran. Received November 22, 1999. Accepted (revised) December 21, 1999     

Transitions and Phenomenology of α,α-trehalose Polymorphs Inter-conversion

The thermal transitions of α,α-trehalose polymorphs have been carefully studied by differential scanning calorimetry (DSC) at different scan rates. Attention has been paid to the correlation of the thermal data with the proper crystalline forms (when present), in order to attribute the observed transitions correctly. In particular, the subtle dehydration process of dihydrate trehalose has been already shown to produce several species, depending on the experimental conditions. Thermodynamic data (i.e., temperatures and enthalpies) for all the known transitions are reported and the results are critically discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reaction of 5-allyl-2,5-dichloro-4,4-dimethoxy-3-morpholinocyclopent-2-enone with Me3SiI

5-Allyl-2,5-dichloro-4,4-dimethoxy-3-morpholinocyclopent-2-enone reacts with Me₃SiI in MeCN to give the corresponding product of reductive vinylic monodechlorination. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1660–1661, August, 1998.     

Boron chelates in the synthesis of α,β-unsaturated ketones of the coumarin series

Condensation of aromatic aldehydes with 3(8)-acetyl-4(7)-difluoroboryloxycoumarin intramolecular complexes gave boron complexes of α,β-unsaturated ketones, whose hydrolysis afforded the corresponding hydroxy cinnamoylcoumarins. The boron complexes and their hydrolysis products intensely absorb and fluoresce in the visible region of the spectrum. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2144–2150, December, 2006.     

Asymmetric reduction of ketones with sodium aluminum hydride modified by various chiral diols

New stereoselective reducing reagents were preparedin situ by modification of NaAlH₄ with various chiral diols. The efficiency of 1,4- and 1,3-diols as chiral auxiliaries in the reactions of alkyl aryl ketones with modified NaAlH₄ was considerably higher than that of 1,2-diols. The effect of the nature of the achiral ligand additionally introduced into the chiral hydride reagent on the enantioselectivity of ketone reduction was studied. It was proposed that the sodium cation does not necessarily participate at the stage governing the reaction stereochemistry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp 459–464, March, 2000.     

Determination of α-aminonitriles, α-amino acid amides and α-amino acids by means of HPLC,post-column reaction and fluorescence detection

Summary An HPLC method was developed for the simultaneous assay of intermediate (α-aminonitrile and α-amino acid amide) and end products (α-amino acid) in process streams of α-amino acid synthesis. Applications are given for Ala, Val and Leu. α-Aminonitriles were stable in a phosphate buffer pH 3, which was subsequently used for sample handling and chromatography. The α-aminonitrile, the corresponding acid amide and α-amino acid were separated using a buffered ion-pair mobile phase on an RP column and were detected fluorimetrically after post-column reaction with fluorescamine. Linearity and precision of the method are given.     

New reaction pathway of dialkyl phosphorochloridites with salts of α-benzylideneaminocarboxylic acids. Direct synthesis of α-aminophosphonates from isostructural α-benzylideneaminocarboxylic acids

The reaction of sodium N-benzylidenevalinate with dialkyl phosphorochloridites is accompanied by decarboxylation and yields diastereomeric N-(1-dialkoxyphosphoryl-2-methylpropyl)-N-(1-dialkoxyphosphorylbenzyl)amines. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1449–1452, June, 2005.     

Synthesis and antimycobacterial activity of some steroidal derivatives of tigogenin

Some 5α-type steroidal derivatives of the steroidal sapogenin tigogenin were synthesized. The structures of the synthesized derivatives were characterized by spectral methods and elemental analysis. The antituberculosis activity of the compounds toward Mycobacterium tuberculosis strain H37Rv was studied in vitro (Microplate Alamar Blue Assay) in BACTEC 12B medium and was compared with that of isoniazide. Some of the synthesized compounds exhibited high (92-98%) antimycobacterial activity. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 332-334, May-June, 2009.