Chemical synthesis of cyclodextrins by using intramolecular glycosylation

An efficient synthesis of cyclodextrins (CDs) by using the intramolecular glycosylation is demonstrated. alpha-CD, an alpha(1-->4)linked hexaglucoside, was prepared via a block condensation of three maltose units. A modified key maltose intermediate as a precursor to both glycosyl donor and acceptor components was prepared in 6 steps starting from maltose. All the glycosylation for chain elongation and cyclization of saccharides was carried out after tethering the donor to the acceptor by the phthaloyl bridge to give the desired saccharides in good yields with complete alpha-selectivity. delta-CD composed of 9 glucose units was synthesized by the same manner from three maltotriose units.     

Studies on the constituents of Lonicera species. XVII. New iridoid glycosides of the stems and leaves of Lonicera japonica THUNB

Four new iridoid glycosides, named L-phenylalaninosecologanin (1), 7-O-(4-beta-D-glucopyranosyloxy-3-methoxybenzoyl)secologanolic acid (2), 6'-O-(7alpha-hydroxyswerosyloxy)loganin (3) and (Z)-aldosecologanin (5), were isolated, together with a known one, newly named (E)-aldosecologanin (4), from the stems and leaves of Lonicera japonica. Their structures were established on the basis of chemical and spectral data.     

Investigation of the crystal structure and the structural and magnetic properties of SrCu2(PO4)2

SrCu2(PO4)2 was prepared by the solid-state method at 1153 K. Its structure was solved by direct methods in the space group Pccn (No. 56) with Z = 8 from synchrotron X-ray powder diffraction data measured at room temperature. Structure parameters were then refined by the Rietveld method to obtain the lattice parameters, a = 7.94217(8) A, b = 15.36918(14) A, and c = 10.37036(10) A. SrCu2(PO4)2 presents a new structure type and is built up from Sr2O16 and Cu1Cu2O8 units with Cu1...Cu2 = 3.256 A. The magnetic properties of SrCu2(PO4)2 were investigated by magnetic susceptibility, magnetization up to 65 T, Cu nuclear quadrupole resonance (NQR), electron-spin resonance, and specific heat measurements. With spin-dimer analysis, it was shown that the two strongest spin-exchange interactions between Cu sites result from the Cu1-O...O-Cu2 and Cu2-O...O-Cu2 super-superexchange paths with Cu1...Cu2 = 5.861 A and Cu2...Cu2 = 5.251 A, and the superexchange associated with the structural dimer Cu1Cu2O8 is negligible. The magnetic susceptibility data were analyzed in terms of a linear four-spin cluster model, Cu1-Cu2-Cu2-Cu1 with -2J(1)/kB = 82.4 K for Cu1-Cu2 and -2J(2)/k(B) = 59 K for Cu2-Cu2. A spin gap deduced from this model (Delta/kB = 63 K) is in agreement with that obtained from the Cu NQR data (Delta/kB = 65 K). A one-half magnetization plateau was observed between approximately 50 and 63 T at 1.3 K. Specific heat data show that SrCu2(PO4)2 does not undergo a long-range magnetic ordering down to 0.45 K. SrCu2(PO4)2 melts incongruently at 1189 K. We also report its vibrational properties studied with Raman spectroscopy.     

Isolation and structure determination of a new marine toxin,neosurugatoxin, from the Japanese Ivory Shell, Babylonia japonica.

A new toxin, named neosurugatoxin, was isolated from the toxic Japanese Ivory Shell and its structure was determined by X-ray crystallographic analysis.     

Stir bar sorptive extraction with in situ derivatization and thermal desorption-gas chromatography-mass spectrometry for determination of chlorophenols in water and body fluid samples

A new method, stir bar sorptive extraction (SBSE) with in situ derivatization and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of chlorophenols, such as 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TrCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP), in tap water, river water and human urine samples, is described. The derivatization conditions with acetic acid anhydride and the SBSE conditions such as extraction time are investigated. Then, the stir bar is subjected to TD followed by GC-MS. The detection limits of the chlorophenols in tap water, river water and human urine samples are 1-2, 1-2, and 10-20 pg ml⁻¹ (ppt), respectively. The calibration curves for the chlorophenols are linear and have correlation coefficients higher than 0.99. The average recoveries of the chlorophenols in all the samples are higher than 95% (R.S.D. < 10%) with correction using added surrogate standards, 2,4-dichlorophenol-d₅, 2,4,6-trichlorophenol-¹³C₆, 2,3,4,6-tetrachlorophenol-¹³C₆ and pentachlorophenol-¹³C₆. This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of chlorophenols in liquid samples.     

Catalytic specificity exhibited by p-sulfonatocalix[n]arenes in the methanolysis of N-acetyl-l-amino acids

Specific acid catalysis of p-sulfonatocalix[n]arenes (n = 4, Calix-S4; n = 6, Calix-S6; n = 8, Calix-S8) was observed in the alcoholysis of N-acetyl-l-amino acids in methanol. The methanolysis rates of basic amino acid substrates (His, Lys, and Arg) were markedly enhanced in the presence of Calix-Sn, as compared with rates observed with p-hydroxybenzenesulfonic acid (pHBS), which is a noncyclic analogue of Calix-Sn. This catalytic effect of Calix-Sn was not observed for the methanolysis of Phe, Tyr, and Trp substrates. On the other hand, (1)H NMR experiments following the effect of Calix-Sn on N-acetyl-l-amino acid substrates in CD(3)OD showed that the spectrum of a mixture of the His substrate with Calix-Sn was significantly different from the combined spectra of the respective compounds. These changes in spectra support the formation of an inclusion complex of Calix-Sn with basic amino acids. Furthermore, it was obvious that methanolysis of the His substrate catalyzed by Calix-S4 and Calix-S6 obeyed Michaelis-Menten kinetics. These results indicate that the catalytic activity of Calix-Sn originates from its forming a complex with specific substrates (basic amino acids), similar to enzymatic reactions.     

Penning ionization electron spectroscopy of C6H6 by collision with He*(2 3 S) metastable atoms and classical trajectory calculations: optimization of ab initio model potentials

The potential energy surface of benzene (C(6)H(6)) with a He*(2(3)S) atom was obtained by comparison of experimental data in collision-energy-resolved two-dimensional Penning ionization electron spectroscopy with classical trajectory calculations. The ab initio model interaction potentials for C(6)H(6)+He*(2(3)S) were successfully optimized by the overlap expansion method; the model potentials were effectively modified by correction terms proportional to the overlap integrals between orbitals of the interacting system, C(6)H(6) and He*(2(3)S). Classical trajectory calculations with optimized potentials gave excellent agreement with the observed collision-energy dependence of partial ionization cross sections. Important contributions to corrections were found to be due to interactions between unoccupied molecular orbitals and the He*2s orbital. A C(6)H(6) molecule attracts a He*(2(3)S) atom widely at the region where pi electrons distribute, and the interaction of -80 meV (ca. -1.8 kcal/mol) just cover the carbon hexagon. The binding energy of a C(6)H(6) molecule and a He* atom was 107 meV at a distance of 2.40 A on the sixfold axis from the center of a C(6)H(6) molecule, which is similar to that of C(6)H(6)+Li and is much larger than those of the C(6)H(6)+[He,Ne,Ar] systems.     

Garcinielliptone G from Garcinia subelliptica Induces Apoptosis in Acute Leukemia Cells

Cytotoxicity and apoptosis-inducing properties of compounds isolated from Garcinia subelliptica leaves were investigated. The hexane-soluble portion of MeOH extracts of G. subelliptica leaves that showed cytotoxic activity was separated to yield seven compounds 1–7. Chemical structure analysis using NMR spectroscopy and mass spectrometry confirmed that compound 1 was canophyllol, and compounds 2–7 were garcinielliptones N, O, J, G, F, and garcinielliptin oxide, respectively. Among them, garcinielliptone G (5) showed growth inhibition by causing apoptosis in THP-1 and Jurkat cells derived from human acute monocytic leukemia and T lymphocyte cells, respectively. Apoptosis induced by garcinielliptone G (5) was demonstrated by the detection of early apoptotic cells with fluorescein-labeled Annexin V and increases in cleaved caspase-3 and cleaved PARP protein levels. However, the addition of caspase inhibitor Z-VAD-FMK did not affect growth arrest or apoptosis induction. These results suggest that garcinielliptone G (5) can induce both caspase-3 activation and caspase-independent apoptosis. Therefore, garcinielliptone G (5) may be a potential candidate for acute leukemia treatment.     

Infrared spectra of the water-nitrogen complexes (H2O)2-(N2)n(n = 1-4) in argon matrices

The infrared spectra of the water-nitrogen complexes trapped in argon matrices have been studied with Fourier transform infrared absorption spectroscopy. The absorption lines of the H20-N2 1:1, 1:2, 1:n, and 2:1 complexes have been confirmed on the basis of the concentration effects. In addition, we have observed a few lines and propose the assignments for the 2:2, 2:3, and 2:4 complexes in the nu1 symmetric stretching and nu2 bending regions of the proton-acceptor molecule, and in the bonded OH stretching region of the proton-donor molecule. The redshifts in the bonded OH stretching mode and blueshifts in the OH bending mode suggest that the hydrogen bonds in the (H2O)2-(N2)n complexes with n = 1-4 are strengthened by the cooperative effects compared to the pure H2O dimer. Two absorption bands due to the 3:n complexes are also observed near the bonded OH stretching region of the H2O trimer.     

Persistent pi radical cations: self-association and its steric control in the condensed phase

Pi Radical cations, which are highly reactive in general, can be made persistently stable by appropriate structural modification with heteroatoms, pi-conjugated systems, and alkyl substituents. Many of these pi radical cations undergo self-association in the condensed phase. The steric control of such self-association of stabilized pi radical cations is the subject of the present article. Such an association can result in the formation of pi- and/or sigma-dimers. The pi-dimerization in particular is now considered as an important intermolecular interaction for model studies of a charge-transport phenomenon in positively doped conducting polymers. On the other hand, the intermolecular interactions can be suppressed when the pi-system is modified with sterically demanding structural units, for example, by annelation with bicycloalkene frameworks. This structural modification not only brings about unusual stabilization of the radical cations but provides valuable information on the electronic structure/properties of the positively charged pi-systems in a segregated state.