Quantum chemical calculation of gas-phase borenium ions

Conclusions A CNDO/2 calculation of C₃H₇NB⁺ borenium ions predicts the greater thermodynamic stability of cyclic structures in comparison with the corresponding acyclic structures.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2619–2620, November, 1987.     

1,2,2-Trimethyldisilane-1,1,2-triol: intermediate formation and conversion to condensation products

1,2,2-Trimethyldisilane-1,1,2-triol (1) is formed as an unstable intermediate upon hydrolysis of oligo(trimethyldisilanylsesquiazane). In the absence of trapping agents it undergoes rapid condensation to give ether-soluble poly(trimethyldisilanyloxane) which contains silanol groups. Treatment of the hydrolysis products with chlorotrimethylsilane in the presence of triethylamine affords trimethylsiloxy derivatives, (Me₃SiO)₂MeSiSiMe₂(OSiMe₃),5,6, and [Si₂Me₃O _x (OSiMe₃) _y ] _n . The isolation of these products indicates that disilanetriol1 readily undergoes condensation to form hydroxylcontaining six-membered rings and polysiloxanes. The condensation of compound1 in the presence of Me₃SiOH has been studied. The ratio between the isomeric cyclosiloxanes5 and6 has been determined both by¹H NMR spectroscopy and by a chemical method (chlorinolysis). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1788–1792, October, 1993.     

Triterpene glycosides and their genins fromThalictrum foetidum. I. The structure of foetoside C

A new glycoside — foetoside C — has been isolated from the epigeal part ofThalictrum foetidum L. and, on the basis of chemical transformations and spectral characteristics its structure has been established as oleanolic acid 28-[O-α-D-glycopyranosyl-(1 → 6)-O-β-D-glucopyranoside] 3-O-[O-β-D-xylopyranosyl-(1 → 3)-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranoside].     

A simple direct enzyme immunoassay of antibodies based on the differences in diffusion rates in a gel of a synthetic antigen and of its complex with antibodies

A simple direct enzyme immunoassay for semiquantitative detec tion of antibodies is suggested. It is based on the difference in diffusion rates in a gel for a synthetic low-mol-wt antigen and of its complexes with antibodies to be detected. Sensitivity and specificity of the devel oped assay are equal to an ELISA method. The assay has been tested with antibodies against HIV protein gp41 in rabbit serum. Possible applications and limitations of the method are discussed.     

Coumarins fromPhlojodicarpus sibiricus

Phlojodicarpin [8-(2,3-epoxy-1-hydroxy-3-methylbutyl)-7-methoxycoumarin, C₁₅H₁₆O₅, mp 143–145°C, [] _D ²⁵ -37.5°], and isophlojodicarpin [8-(1,2-epoxy-3-hydroxy-3-methylbutyl)-7-methoxycoumarin, C₁₅H₁₆O₅, mp 132–134°C, [] _D ²⁵ -102.5°] have been isolated from the epigeal part ofPhlojodicarpus sibiricus. The results of the IR, UV, PMR, and mass spectrometry of these compounds are given.Institute of Chemistry, Academy of Sciences of the Mongolian Peoples' Republic, Ulan-Bator. Irkutsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 47–49, January–February, 1981.     

Acid-base properties of indolylglyoxal and some acetylindoles

A spectrophotometric study of the acid-base properties of 3-acylindoles showed that they were stronger acids than the alkylindoles. It was found that protonation of these compounds occurs at the carbonyl group. For indolylglyoxal, 3-acetylindole, and 1-methyl-3-acetylindole the pK_b was determined; the pK_afor indolylglyoxal and 3-acetylindole was measured in 50% aqueous methanol.Translated from Khimiya Geterotsiklicheskhikh Soedinenii, No. 12, pp. 1621–1624, December, 1987.     

New triterpene glycosides fromThalictrum squarrosum St. ex Willd. The structure of squarrosides B3 and B4

From the above-ground part ofThalictrum squarrosum St. ex Willd. (Ranunculaccae), an equilibrium mixture of two triterpene glycosides, squarrosidc B3 (1), 3-O-[O-(-L-rhamno-pyranosyl)-(16)--D-glucopyranosyl]-21 (S),22(),23(R)-3,21,22,30-tctralmydroxy-21, 23-cpoxycycloartlt-24-ene, and squarrosidc B4 (2), its 21(R) epimer, was isolated. Their structures were established on the basis of IR and 2D NMR spectra and FAB mass spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1547–1551, June, 1996.These signals coincide for 5 and 6.     

Quaternization of tetrazoles under high pressure and establishment of the structures of quaternary tetrazolium salts by 13C NMR spectroscopy

The quaternization of 1- and 2-acetonyl-5-R-tetrazoles, as well as dimethyltetrazole, was accomplished under high pressure conditions (5000–14,000 kgf/cm²) by means of bromoacetone and methyl iodide and at atmospheric pressure and room temperature under the influence of methyl fluorosulfate. The structure of the salts were ascertained by ¹³C NMR spectroscopy, and the principles of the change in the chemical shifts and the spin-spin coupling constants during quaternization and protonation of the tetrazoles were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1118–1124, August, 1982.