Total synthesis of bistramide A and its 36(Z) isomers: differential effect on cell division, differentiation, and apoptosis

The total synthesis of bistramide?A and its 36(Z),39(S) and 36(Z),39(R) isomers shows that these compounds have different effects on cell division and apoptosis. The synthesis relies on a novel enol ether-forming reaction for the spiroketal fragment, a kinetic oxa-Michael cyclization reaction for the tetrahydropyran fragment, and an asymmetric crotonylation reaction for the amino acid fragment. Preliminary biological studies show a distinct pattern of influence of each of the three compounds on cell division, differentiation, and apoptosis in HL-60 cells, thus suggesting that these effects are independent activities of the natural product.     

Synthesis of 4-aminoguaiazulene and its δ-lactam derivatives

A method for nitrogen insertion into guaiazulene hydrocarbons is developed. A one-pot reaction of 7-isopropyl-1-methylazulene-4-carboxylic acid, diphenylphosphoryl azide, and an alcohol (MeOH, ^tBuOH or BnOH) affords the corresponding carbamates. Deprotection of benzyl (7-isopropyl-1-methylazulen-4-yl)carbamate under basic conditions gave 4-aminoguaiazulene, which undergoes ring annulation reactions with 1,2-dicarbonyl reagents to yield tricyclic δ-lactams.     

The Sonogashira Coupling of Polymer‐Supported Propargylamine with Aryl Iodides

The Sonogashira coupling reaction of polymer‐supported propargylamine (=prop‐2‐yn‐1‐amine) with aryl iodides in the presence of the [Pd(PPh₃)₂]Cl₂/CuI catalyst system produces 3‐arylprop‐1‐yn‐1‐amines smoothly at room temperature (Scheme). When propargylamine is attached on Wang resin through a carbamate linker, the common problems with amino functionality in palladium‐catalyzed couplings are overcome. The arylpropynamines are cleaved from the polymer with CF₃COOH and converted into chromatographically easily separable acetamides. Our solid‐phase method opens a new pathway toward precursors of pharmacologically interesting arylpropynamines and arylpropanamines.     

Impossibility of Stokes decomposition for a class of light beams

Decomposition throughout all space of a typical light beam into the sum of a completely polarized and a completely unpolarized beam (Stokes decomposition) seems to be rather the exception than the rule. However, it is known that such decomposition can often be made across a certain plane, although it may lose validity upon propagation. Then, one may guess that, for any light beam, there exists at least one plane where the Stokes decomposition can be performed. Without adopting any particular model for polarized and unpolarized beams, we present a class of beams for which no such plane can exist.     

Birch inner bark procyanidins can be resolved with enhanced sensitivity by hydrophilic interaction HPLC-MS

A complex mixture of procyanidin aglycones was isolated by Sephadex LH-20 column chromatography from the silver birch inner bark, which is a polyphenol-rich source of natural antioxidants. Procyanidins were studied by using hydrophilic interaction liquid chromatography combined with high-resolution ESI-TOF-MS. A good chromatographic separation was achieved and procyanidins eluted according to their increasing degree of polymerization. Individual procyanidins were detected from dimers up to the degree of polymerization of 22 by their negative-ion mass spectra. The results showed that hydrophilic interaction liquid chromatography can be successfully applied for the analysis of high-molecular-weight procyanidins with enhanced sensitivity in electrospray mass spectrometry.     

Spirocyclic Boraamidinate Complexes of Lanthanide(III) Metals

The reaction of Li₂[Phbam^Dipp] (Phbam^Dipp = PhB(NDipp)₂; Dipp = 2,6‐iPr₂C₆H₃) with lanthanum(III) triiodides LnI₃(THF)_3.5 (Ln = La, Sm) in THF produces complexes of the type [Li(THF)₄]₂[(Phbam^Dipp)₂LnI], which were characterized in solution by multinuclear NMR spectroscopy and in the solid state by single‐crystal X‐ray structural determinations. The ion‐separated complexes are comprised of a spirocyclic anion in which two Phbam^Dipp ligands and an iodide ion are linked to the five‐coordinate metal atom; charge balance is provided by two tetrasolvated lithium ions [Li(THF)₄]⁺.     

Detection of volatile organic compounds by temperature-programmed desorption combined with mass spectrometry and Fourier transform infrared spectroscopy

A temperature-programmed desorption (TPD) device connected to a mass spectrometer was used to detect volatile organic compounds from air samples. The main aim was to develop an analytical method, by which both non-polar and polar organic components can be detected in the same run. In TPD, the adsorbed compounds are desorbed from the resin more slowly than in the conventional trapping techniques, such as purge-and-trap technique, in which the resin is flash-heated and the compounds are desorbed at the same time to a cryogenic trap or an analytical column. In TPD, the adsorbent resin acts also as an analytical column. In this way it is possible to obtain more rapid analysis, and also a more simple instrumentation, which can be used on-line and on-site. In this work, a new version of TPD device, which uses a resistor for heating and a Peltier element for rapid cooling, was designed and constructed. Various adsorbent resins were tested for their adsorption and desorption properties of both polar and non-polar compounds. When using a mixture of adsorbent resins, Tenax TA and HayeSep D, it was possible to analyze both polar, low-molecular weight compounds, such as methanol and ethanol, and non-polar volatile organic compounds, such as benzene and toluene, in the same run within 15 min including sampling. The same TPD principle was also tested using a Fourier transform infrared spectrometer as an analytical instrument, and the results showed that it was possible to obtain a separation of similar compounds, such as hexane and heptane, and still retaining the same sensitivity as the original on-line FTIR instrument.     

Synthesis, spectroscopic, and structural investigation of the cyclic [N(PR2E)2]+ cations (E = Se, Te; R = iPr, Ph): the effect of anion and R-group exchange

Two-electron oxidation of the [N(PiPr2E)2]- anion with iodine produces the cyclic [N(PiPr2E)2]+ (E =Se, Te) cations, which exhibit long E-E bonds in the iodide salts [N(PiPr2Se)2]I (4) and [N(PiPr2Te)2]I (5). The iodide salts 4 and 5 are converted to the ion-separated salts [N(PiPr2Se)2]SbF6 (6) and [N(PiPr2Te)2]SbF6 (7) upon treatment with AgSbF6. Compounds 4-7 were characterized in solution by multinuclear NMR, vibrational, and UV-visible spectroscopy supported by DFT calculations. A structural comparison of salts 4-7 and [N(PiPr2Te)2]Cl (8) confirms that the long E-E bonds in 4, 5, and 8 can be attributed primarily to the donation of electron density from a lone pair of the halide counterion into the E-E sigma* orbital (LUMO) of the cation. The phenyl derivative [N(PPh2Te)2]I (9) was prepared in a similar manner. However, the attempted synthesis of the selenium analogue, [N(PPh2Se)2]I, produced a 1:1 mixture of [N(PPh2Se)2(mu-Se)][I] (10) and [SeP(Ph2)N(Ph2)PI] (11). DFT calculations of the formation energies of 10 and 11 support the observed decomposition. Compound 10 is a centrosymmetric dimer in which two six-membered NP2Se3 rings are bridged by two I- anions. Compound 11 produces the nine-atom chain {[N(PPh2)2Se]2(mu-O)} (12) upon hydrolysis during crystallization. The reaction between [(TMEDA)NaN(PiPr2Se)2] and SeCl2 in a 1:1 molar ratio yields the related acyclic species [SeP(iPr2)N(iPr2)PCl] (13), which was characterized by multinuclear NMR spectroscopy and an X-ray structural determination.     

Analysis of volatile sesquiterpenoids in environmental and geological samples

In order to evaluate vloatile compounds, especiallly sesquiter-penoids, in environmental and geological samples a method was penoids, in environmental and geological samples a method was required to characterize these components when they occur at low concentrations. After fractionation of the total sample extracts by TLC the aliphatic fractions were analyzed by HRGC AND THE kovats indices of all resolved peaks were calculated and comkpared with indices of all resolved peaks were calculated and compared with those obtained for commercial standards. As final step, the fractions were analyzed by HRGC-MS and structures confirmed by comparison of their mass spectra with those of certified sesuiterpene standards. Additionally sesquiterpenoids present in the dissolved phase in water samples were concentrated by solid phase extraction using XAD-2 resin. In this initial study, recovery tests with the resin were carried out in order to evaluate its performance rather than validating the methodology.     

Anionic phospholipid coatings in capillary electrochromatography. Binding of Ca2+ to phospholipid phosphate group

Anionic phospholipids phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylinositol (PI), and phosphatidylserine (PS) were examined for their effect on 1-palmitoyl-2-oleyl-sn-glycero-3-phosphatidylcholine (POPC)-containing liposomes used as coating material in capillary electrochromatography. Liposome solvent was N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (HEPES) buffer at pH 7.4 with and without 3 mM of CaCl2. The background electrolyte solution was HEPES buffer at pH 7.4. The net charge, size, and short-term stability of the liposomes were measured with a Zetasizer. Results showed that calcium interacts with all liposomes but most strongly with POPC/PA. The relative migration times, retention factors, and resolution of the model analytes (one cationic, three uncharged ions, and one anionic) were studied. All liposomes successfully coated the silica capillary. Without calcium the strongest interaction and best separation of the analytes were with the POPC/PI and POPC/PS coatings, while interactions with the POPC/PA coating were weak. Calcium enhanced the interactions of the model analytes with all coatings, and the interactions were then strongest with the POPC/PA coating. In the presence of calcium there appears to be a slight reorganization of the coating with increasing number of runs. Our results indicate strong interactions between calcium and the phosphate groups in phospholipids and demonstrate the significant role of the phospholipid polar head group in phospholipid coatings on silica surfaces.