3β-Methoxyolean-18-ene (miliacin) from the marine fungus Chaetomium olivaceum

A pentacyclic tritepenoid, 3gif" alt="beta" align="MIDDLE" BORDER="0">-methoxyolean-18-ene (miliacin), was isolated for the first time from the marine fungus Chaetomium olivaceum. Its structure was determined on the basis of 2D NMR spectroscopy and X-ray diffraction data.     

Molecule-Responsive Fluorescent Sensors of α-Helix Peptides Bearing α-Cyclodextrin, Pyrene and Nitrobenzene Units in Their Side Chains

gif" alt="agr" align="BASELINE" BORDER="0">-Helix peptides bearing one unit of gif" alt="agr" align="BASELINE" BORDER="0">-cyclodextrin (gif" alt="agr" align="BASELINE" BORDER="0">-CD), one unit of pyrene and one unit of nitrobenzene (NB) in their side chains have been designed and synthesized as novel molecule-responsive devices.In both the CD-peptides, gif" alt="agr" align="BASELINE" BORDER="0"> -PR17 and gif" alt="agr" align="BASELINE" BORDER="0"> -PL17, the NB unit is separated from the CD unit by two turns of the helix. Two reference peptides (PL17, and -P17,) have also been synthesized. The circular dichroism studies in the peptide absorption region (200–250 nm)of gif" alt="agr" align="BASELINE" BORDER="0"> -PR17 and gif" alt="agr" align="BASELINE" BORDER="0"> -PL17 suggestthat the CD-peptides form stablegif" alt="agr" align="BASELINE" BORDER="0">-helixstructures (83–77%), which was destabilized by accommodating guest molecules (e.g., n-pentanol) into the CD cavity. It suggests that formation of intramolecular host–guest(CD–NB) complex stabilized thehelical structure and exogenous guest molecule excluded the appending NB moiety from inside to outside of the CD cavity, thereby causing destabilization of the helical structure and increasing the random coil content. The ICD spectra of the peptides in the pyrene and nitrobenzene absorption region (250–40 nm) suggest that NB forms inclusion complex with CD. The fluorescence studies revealed that the fluorescence of the pyrene unit is quenched by the NB unit in gif" alt="agr" align="BASELINE" BORDER="0"> -PR17 and gif" alt="agr" align="BASELINE" BORDER="0"> -PL17. The fluorescence intensity increases with increasing guest concentration for the CD-peptides.This guest-responsiveenhancement in the fluorescence intensity can be explained in terms of increased distance between the pyrene and NB moieties, which is caused by exclusion of the NB moiety from the CD cavity by guest accommodation. Using the guest-responsive fluorescence quenching properties of the CD-peptides, we have obtained binding constants for various short chain alkanols.gif" alt="agr" align="BASELINE" BORDER="0"> -PL17 has higher binding affinity to the guest molecules than its isomer, gif" alt="agr" align="BASELINE" BORDER="0"> -PR17, indicating that the location of functional groups on the peptide scaffold is important in molecule detection.     

Naphthalene Complexation by β-Cyclodextrin: Influence of Added Short Chain Branched and Linear Alcohols

Naphthalene forms 1 : 1 complexes with gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (gif" alt="beta" align="MIDDLE" BORDER="0">-CD)in water. The binding constant is 377 ± 35 M^-1. Addition of linear or branched alcohols causes a reduction in the apparent strength of naphthalene binding (K_app) compared to the value in the absence of additives. For example, 1% 1-pentanol reduces K_app to 184 ± 31 M^-1. Branching does not alter K_app much for a given number of carbon atoms, e.g., it is 113 ± 9 M^-1for 2-pentanol and 116 ± 8 M^-1for 3-pentanol. The exception to this is tert-butanol for which K_app is 577 ± 40 M^-1. The variation in K_app as a function of [1-pentanol] yields values for the individual equilibrium constants contributing to K_app. This reveals that a ternary complex forms involving naphthalene, the CD and 1-pentanol. The constant for formation of the ternary complex is 99 ± 29 M^-2. NaI quenching of naphthalene fluorescence indicates that the CD cavity partially protects the naphthalene excited state fromthis water phase quencher. Interestingly, the Stern–Volmer constant is lower in the presence of 1-pentanol than in its absence, although there should be more unbound (and therefore more NaI accessible) naphthalene in the former system than in the latter. These apparently contradictory results are discussed in terms of ternary complex formation.     

One-step synthesis of the chelate oxides of bis(trialkylantimony) by an oxidative method

The chelate oxides of bis(trimethylantimony) (Me₃SbL¹)₂O (i = 1 or 2, L¹-acetylacetonate, L² - trifluoroacetylacetonate) and bis(triethylantimony) (Et₃SbL¹)₂O have been obtained in 79–85% yields by a one-step oxidation of trialkylantimony withtertbutylhydroperoxide in the presence of gif" alt="beta" align="MIDDLE" BORDER="0">-diketones in benzene at 20 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 154–155, January, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 94-03-08846).     

Preparation and characterization of theβ-cyclodextrin inclusion complex with sulfafurazole

The 1 : 1 inclusion complex involving sulfafurazole (SF) andgif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin (gif" alt="beta" align="MIDDLE" BORDER="0">-CD) is prepared by the freeze-drying method and characterized on the basis of its chemical analysis, thermal behavior, infrared spectrum, X-ray powder pattern and¹³C NMR spectrum in DMSO-d₆ solution. The stability constant of the inclusion complex was determined by the solubility method. The effect of cyclodextrin on the UV absorption spectrum of sulfafurazole was also observed.     

The inclusion of rhodium(II)α-methyl-cinnamate in β-cyclodextrin

The preparation and characterization of the 1:1 inclusion compound of rhodium(II) gif" alt="agr" align="BASELINE" BORDER="0">-methyl cinnamate in gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin is reported. Evidence of inclusion was obtained from X-ray powder diffraction results, Raman, IR and UV-Vis spectroscopic studies and thermal analysis. Given the potential antitumor activity of the rhodium(II) carboxylate and its virtual insolubility in water, its inclusion in gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin opens the possibility for its transference to the aqueous phase.     

Synthesis of phosphorus (silicon,tin)-containing derivatives of mercaptoketenes and some of their properties

Some newS-phosphorylated,S-silylated, andS-stannylated derivatives of gif" alt="agr" align="BASELINE" BORDER="0">-mercaptoketones were obtained. The reactions of some of these compounds induced by the temperature and by molecular oxygen as well as the phosphorylation of the Si- and Sn-containing derivatives were studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 353–357, February, 1995.     

Enantiomer differentiation in intramolecular carbon—hydrogen insertion reactions of racemic secondary alkyl diazoacetates catalyzed by chiral dirhodium(ii) carboxamidates

Highly efficient kinetic resolution of racemic secondary alkyl diazoacetates in intramolecular carbon-hydrogen insertion reactions has been achieved using chiral dirhodium(ii) carboxamidates. Products formed from catalytic diazo decomposition of racemic 2-octyl diazoacetate and, separately, its (2R)- and (2S)-enantiomeric forms, as well as bothcis- andtrans-2-methylcyclohexyl diazoacetates, have been systematically evaluated. Enantioselectivities up to 99 %ee have been obtained for gif" alt="gamma" align="MIDDLE" BORDER="0">-lactone formation. gif" alt="beta" align="MIDDLE" BORDER="0">-Lactone production has been observed and, although minor with cyclohexyl diazoacetates, is the major insertion pathway for diazo decomposition of 2-octyl diazoacetate.Dedicated to Academician of the RAS N. S. Zefirov (on his 60th birthday).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1798–1803, September, 1995.Financial support for this research from the National Institutes of Health (GM 46503) and the National Science Foundation of the United States is gratefully acknowledged. We thank D. A. Pierson for her preparation of 2-methylcyclohexyl diazoacetates and preliminary studies of their diazo decomposition and A. Melekhov from the Higher College of Chemistry for his preparation and catalytic studies of rac-2-octyl diazoacetate.     

The influence of cyclodextrin complexation on proton transfer in piperidinomethyl-2-naphthol

Summary Piperidinomethyl-2-naphthol forms inclusion complexes with gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin with an equilibrium constant of 265M ^–1 in aqueous solution. The proton transfer equilibrium between the neutral and the zwitterionic form is strongly influenced by the association.

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Der Einfluß der Komplexierung mit gif" alt="beta" align="MIDDLE" BORDER="0">-Cyclodextrin auf das Protontransfer-Gleichgewicht in Piperidino-2-naphthol (Kurze Mitt.)

Zusammenfassung Piperidinomethyl-2-naphthol bildet Einschlußkomplexe mit gif" alt="beta" align="MIDDLE" BORDER="0">-Cyclodextrin mit einer Gleichgewichtskonstante von 265M ^–1. Das Protontransfer-Gleichgewicht zwischen neutraler Form und zwitterionischer Struktur wird durch diese Assoziation stark beeinflußt.

     

Base-catalyzed cyclization of β-(2-arylaminoethoxy)styrenes

gif" alt="beta" align="MIDDLE" BORDER="0">-(2-Arylaminoethoxy)styrenes undergo cyclization in the presence of KOH to giveN-aryl-2-benzyloxazolidines inca. 90 % yield. The structures of the products were confirmed by IR and NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 340–341, February, 1994.