Chlorinating properties of the trimethylchlorosilane-potassium bromate-DMF system

-Dicarbonyl compounds such as ethyl acetoacetate, dimedone, and Meldrum's acid derivatives undergo monochlorination by the action of a mixture of C1SiMe₃ and KBrO₃ in DMF at 20°C.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 448–450, February, 1992.     

Photochemical addition of diethyl ether to β,β,β',β'-tetrakis(trifluoromethyl)divinyl ether

The 1:1 adducts of diethyl and ,,','-tetrakis(trifluoromethyl)divinyl ether (1),i.e., 3,5-(ee)-bis[2,2,2-trifluoro-1-(trifluoromethyl)ethyl]-2,6-dimethyl-1,4-dioxane (2) (3 isomers) and 4-ethoxy-1,1,1-trifluoro-2-trifluoromethyl-3-[3,3,3-trifluoro-2(trifluoromethyl)propenyloxy]pentane (3), have been obtained by UV-irradiation of a solution of divinyl ether1 in diethyl ether. The X-ray structural investigation of the all-(e)-isomer of dioxane (2) has been carried out.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 85–88, January, 1994.     

Spectroscopic detection of theendo-enol form of 2-acetylcyclopentane-1,3-dione

According to vibrational spectroscopic data, in the gas phase at 280 °C and in crystals prepared by sublimation, 2-acetylcyclopentane-1,3-dione was established to exist not as trione 1 but as the enol-form 2 with an exo-cyclic C=C bond (v(C=C) = 1593 cm^–1) and an intramolecular hydrogen bond. The enol 3 prepared by crystallization from CCl₄ is also stabilized by an intramolecular H-bond but has anendo-cyclic C=C bond (v(C=C) = 1545 cm^–1). In a trichloroethylene solution, both theexo- andendo-enol forms co-exist, and the percentage of the latter is 11 %. The frequencies in the vibrational spectra have been assigned using the normal coordinate calculation of2, 3, and their OD-analogs. The mechanism of tautomer transfer is discussed in terms of PMO theory.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 57–62, January, 1994.The authors are grateful to professor J. G. Ramos (Madrid Institute of Optics) for making it possible to record the far IR and Raman spectra in his laboratory, to Dr. V. Z. Kurbako for the registration of spectra and its discussion, and to Dr. N. A. Kubasova for recording the Raman spectra with a Coderg Ar-300 instrument.     

Reaction of β-Cyclodextrin with N-2,3-Epoxypropylphthalimide. Preparation, Characterisation and Study of a New Substituted Cycloheptaamylose. Effects on the Water Solubility of Drugs

The reaction of -cyclodextrinwith N-2,3-epoxypropylphthalimide yielded a set of newamorphous host compounds with high solubility whichwas transmitted to the corresponding host-guestcomplexes. The structure was determined by comparing the 1H- and 13C-NMR spectra with those of theparent compound, the degree of substitution by integration of the corresponding NMR signals, and C, H,and N elemental analysis.     

Transformationen von β-Glycofuranosylisocyaniden in Tetrahydrofuranderivate

Summary Readily available -glycofuranosyl isocyanides1,2,4,5,6,18,19,20 are transformed into the corresponding protected tetrahydrofurans21,22,23,24,25,26 by means of tributyltin hydride andAIBN. The synthesis of18 and19 by dehydration of the formamide15 is described. Starting with 6-deoxy-1,2-O-isopropyliden--D-allofuranose (7) crystalline 1,2-O-diacetyl-3,5-dibenzoyl--D-allofuranose (9) is obtained.9 is first transformed into the anomeric azides11,12 and13,14 and subsequently into the formamide15.

     

Improvement of Solubility and Dissolution of 19-Norprogesterone via Inclusion Complexation

In an effort to modify the solubility and dissolution rate of the contraceptive steroid, 19-norprogesterone in order to improve its bioavailability, the cyclodextrin complexation approach was chosen. In solution, the complex formation with -cyclodextrin (-CD), hydroxyethyl -cyclodextrin (HE--CD) and hydroxypropyl -cyclodextrin (HP--CD) was confirmed by using solubility, UV, IR and ¹H-NMR spectrophotometric techniques. The phase solubility diagrams were categorized as A_L-type. The complexing affinity of the CDs investigated were ranked as follows: -CD > HP--CD > HE--CD. The complexation thermodynamic parameters were obtained from the temperature dependence of the dissociation constants. In the solid state, differential scanning calorimetery (DSC) and optical microscopy methods were utilized to characterize the complexes. Dissolution studies showed that such molecularly encapsulated forms offered a marked improvement in the dissolution rate compared to the parent drug.     

Darstellung und Eigenschaften von 2-Acyl-1,2-thiazetidin-1,1-dioxiden

Title compounds3a–3i were synthesized by acylation of 1,2-thiazetidine 1,1-dioxide by various methods. Spectroscopic data elucidate the conformation and geometry of the fourmembered ring. An X-ray analysis of3i is presented.

     

Nitrosation of mefenorex in the presence of cyclodextrins

- and -Cyclodextrin (CD) and heptakis-2,6-di-O-methyl--cyclodextrin (DIMEB) form soluble inclusion compounds with mefenorex (MEF); with -CD a partial inclusion occurs. No solid inclusion compound could be obtained with the four CDs. -, -CD and DIMEB, but not -CD, enhance the nitrosation rate of MEF if the nitrosation assay procedure (NAP test) is applied. During this reaction with - and -CD, solid inclusion compounds of the CDs and nitrosomefenorex (NMEF) precipitate.Part of the Ph.D. thesis of V. Wedelich, Freie Universität Berlin, 1985.     

Synthesis ofN-alkylamides of 3-fluoroalkylaziridine-2-carboxylic acids

The N-alkylamides of 3-fluoroalkylaziridine-2-carboxylic acids have been prepared for the first time by the interaction of ethyl 0-fltioroalkyl-,-dibromocarboxylates with primary amines.Prepared by a known procedure;² characteristics of previously unknown ester1b are given in the Experimental section.     

Sulfur heterocycles. 13. Oxidative chlorination of β-thiolactones. A novel synthesis of β-(chlorosulfinyl)alkanoyl chlorides and 1,2-oxathiolan-5-one 2-oxides

Chlorination of -thiolactones with chlorine or sulfuryl chloride in acetic anhydride at a reactant ratio (RR) of 1:2:1 gives -(chlorosulfinyl)alkanoyl chlorides in 75–89% yields. Oxidative chlorination of -thiolactones with RR of 1:3:2 affords -(chlorosulfinyl)alkanoyl chlorides and cyclic sulfinic anhydrides (1,2-oxathiolan-5-one 2-oxides). The optimum RR for the preparation of 1,2-oxathiolan-5-one 2-oxides is 1:2:2. Hydrolysis of -chloro--(chlorosulfinyl)carbonyl chlorides has given novel -chlorinated sulfinocarboxylic acids.For communication 12, see [1].A. N. Nesmeyanov Institute of Heteroorganic Chemistry, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2153–2158, September, 1992.     

Synthesis and biological activity of yuccagenin bisrhamnoside

The two hydroxyls of yuccagenin can be glycosylated by Koenigs-Knorr condensation with acetobromorhammose in dichloroethane in the presence of mercuric cyanide. The bisrhamnoside of yuccagenin markedly lowers the cholesterol and triglyceride content in blood serum of healthy animals and animals with experimental hyperlipidemia.Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 242–243, May–June, 2000.     

Crystal structure and fluorescence properties of p-nitrobenzoylanisoylmethane and its complex with boron difluoride

The crystal and molecular structures of p- and m-nitrobenzoylanisoylmethanatoboron difluoride were determined. The spectral luminescence properties of these compounds were studied and compared.     

Charge-transfer complexes betweenp-toluidine and iodine in solution: A kinetic study

The kinetics of charge-transfer interaction betweenp-toluidine and iodine in methylene chloride was investigated in depth. Thethermal process of formation of theinner complex was found to proceed to an equilibrium. Thephotochemical process follows a different reaction coordinate, going through the formation of an exciplex between the excitedouter complex and the amine ground state. In both cases the same ionic complex (Am ₂I⁺I ₃ ^– , whereAm stands forp-toluidine) was detected as the final product.

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Kinetische Untersuchung der Charge-Transfer-Komplexe zwischenp-Toluidin und Jod

Zusammenfassung Die Kinetik der Charge-Transfer-Wechselwirkung zwischenp-Toluidin und Jod in Methylenchlorid wurde ausführlich untersucht. Derthermische Prozeß, der zur Bildung desinner-Komplexes führt, geht bis zu einem Gleichgewicht. Derphotochemische Prozeß folgt einer unterschiedlichen Reaktionskoordinate und verläuft über die Bildung eines Exziplexes zwischen dem angeregtenouter-Komplex und dem Amin im Grundzustand. In beiden Fällen wurde derselbe ionische Komplex (Am ₂I⁺I ₃ ^– , wobeiAm fürp-Toluidin steht) als Endprodukt festgestellt.

     

The conformational preferences of γ-lactam and its role in constraining peptide structure

Summary The conformational constraints imposed by -lactams in peptides have been studied using valence force field energy calculations and flexible geometry maps. It has been found that while cyclisation restrains the of the lactam, non-bonded interactions contribute to the constraints on of the lactam. The -lactam also affects the (,) of the residue after it in a peptide sequence. For an l-lactam, the ring geometry restricts to about-120°, and has two minima, the lowest energy around-140° and a higher minimum (5 kcal/mol higher) at 60°, making an l--lactam more favourably accommodated in a near extended conformation than in position 2 of a type II -turn. The energy of the +60° minimum can be lowered substantially until it is more favoured than the-140° minimum by progressive substitution of bulkier groups on the amide N of the l--lactam. The (,) maps of the residue succeeding a -lactam show subtle differences from those of standard N-methylated residues. The dependence of the constraints on the chirality of -lactams and N-substituted -lactams, in terms of the formation of secondary structures like -turns is discussed and the comparison of the theoretical conformations with experimental results is highlighted.     

Spectroscopic and quantum chemical investigation of enol-enol tautomerism of 2-acetyltetronic acid

Vibratonal spectra of 2-acetyltetronic acid (ATA) (3-acetyloxolane-2,4-dione) were investigated in different aggregate states.Ab initio quantum chemical calculations (3-21G basis set) of 2-formyltetronic acid as analogue of ATA and semi empirical calculation of ATA were carried out. The tautomeric forms of ATA can be arranged in the following series with respect to thermodynamic stability (in decresing order):1a,1b,2a,2b.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1043–1048, June, 1995.     

Electrostatic and structural similarity of classical and non-classical lactam compounds

Various electrostatic and structural parameters for a series of classical and non-classical -lactams were determined and compared in order to ascertain whether some specific -lactams possess antibacterial or -lactamase inhibitory properties. The electrostatic parameters obtained, based on the Distributed Multipole Analysis (DMA) of high-quality wavefunctions for the studied structures, suggest that some non-classical -lactams effectively inhibit the action of -lactamases. As shown in this work, such electrostatic parameters provide much more reliable information about the antibacterial and inhibitory properties of -lactams than do structural parameters.     

Interaction of fluoroalkyl-containing β-diketones with amines

The composition of products of the interaction of asymmetric fluoroalkyl-containing -diketones with amines was studied. Mixtures of regioisomeric -aminovinylketones and products of cleavage and secondary condensation are formed, depending on the temperature, the solvent, the nature of the fluorinated and nonfluorinated substituents in the -diketone, and the basicity of the amine. The major product is a -aminovinylketone in which the NH₂ group is removed from the fluoroalkyl substituent. No -aminovinylimines, products of condensation involving two electrophilic centers, were observed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2278–2284, September, 1996.     

Determination of the equilibrium melting point of the β-form of polypropylene

The melting behavior of the -form of isotactic polypropylene (-iPP) was investigated as a function of crystallization time and temperature. Calcium suberate, a selective -nucleating agent was used to produce samples that consist entirely of -form i-PP. The experimental melting points were recorded at different crystallization times and were extrapolated to the start of the crystallization process in order to eliminate the effect of lamellar thickening. Using the non-linear Hoffman—Weeks approach to correlate these extrapolated experimental melting temperatures with the corresponding crystallization temperatures, an equilibrium melting point of 209°C was obtained for -iPP. The equilibrium melting point estimated through the non-linear Hoffman—Weeks analysis is about 30°C higher than that (T _m ⁰=177°C) obtained on the basis of the linear extrapolation. These results are consistent with earlier claims that a linear extrapolation of T _m–T _c data leads to an underestimation of the equilibrium melting point. The results obtained for -iPP exemplify the importance of accounting for both the isothermal lamellar thickening effects and the non-linearity in the T _m–T _c correlation, when the determination of an equilibrium melting point is carried out using a procedure based on the predictions of the Lauritzen—Hoffman secondary nucleation theory.This revised version was published online in November 2005 with corrections to the Cover Date.     

Staged Development of Modified Silicon Dioxide Films

The hydrolytic generation of SiO₂ films from chlorosilanes or alkoxysilanes is interrupted by incorporating labile organic groups which stop SiO₂ formation at a processable prepolymer stage. The monomers for the prepolymer have electron withdrawing substituents in the -position. The organic groups are removed from the prepolymer at low temperature, extruding ethylene. The formation of SiO₂ proceeds by intramolecular condensation of the electronegative substituents which are now in a hydrolytically unstable bond with silicon and hydroxyl groups or ambient moisture. Films of the prepolymer spun onto silicon wafers are converted into uniform SiO₂-rich films at temperatures between 150–400°C.     

Formulation and Preliminary in vivo Testing of Rufloxacin-Cyclodextrin Ophthalmic Solutions

Aim of the present work was to investigate the effect of somecyclodextrins (CDs) on the solubility and ocular bioavailability of rufloxacin base (RUF), with theultimate goal of developing an ophthalmic formulation. Phase solubility studies of RUF inpH 7.4 buffer were carried out in the presence of -cyclodextrin (-CD),hydroxypropyl--cyclodextrin (HP--CD) and -cyclodextrin(-CD). The effect of hydroxypropyl methylcellulose (HPMC) on RUF solubility was evaluated after heating the solutionscontaining HP--CD at 120 °C.A significant enhancement of RUF solubility was achieved by associatingthe drug with CDs, particularly HP--CD. This CD formed with RUF a less stablecomplex than that formed by -CD, but did not suffer the solubility limitations ofthe parent CD, and showed a higher solubilizing capacity than -CD. Addition of 0.25%(w/v) HPMC to solutions containing HP--CD increased the solubilizing effect of this CD,thus allowing reduction of the amount necessary for solubilization of 0.3% (w/v) RUF.Preliminary pharmacokinetic data in rabbits indicated that theocular bioavailability of 0.3% (w/v) RUF solubilized by HP--CD was higher when compared witha 0.3% (w/v) RUF suspension used as reference.