Model experiments on surugatoxin synthesis. an approach in the construction of the pentacyclic ring system

Synthesis of the ethyl ester 2a of the debromo-aglycone of surugatoxin 1 has been achieved in 10 steps starting from readily available ethyl 2-(2-oxo-3-indolenyl)-3-oxo-4-phthalimidobutyrate 3.     

Isotope effect of retention value between64Cu and66Cu in neutron-irradiated copper phthalocyanine

Copper phthalocyanine ( and forms) in neat solid or in dissolved state in conc. H₂SO₄ was neutron-irradiated, and retention values of⁶⁴Cu and⁶⁶Cu were estimated to study whether or not there is any isotope effect in retention between these two (n, )-produced radionuclides. The data show that there is an isotope effect expressed by the ratio of retention of⁶⁶Cu to that of⁶⁴Cu, ranged from 1.29±0.12 for form dissolved in conc. H₂SO₄ to 1.09±0.02 for form in neat solid irradiation. This result coincides with the tendency anticipated from the recoil energy spectra which were computed by a program using Monte-Carlo method.     

Simple and rapid identification of phosphorylated peptides from bovine brain myelin basic protein by reversed-phase high-performance liquid chromatography

The phosphorylation sites of the myelin basic protein from bovine brain were determined after phosphorylation with a cyclic 3':5'-phosphate-dependent protein kinase from the same source. Three phosphorylated peptides were selectively and rapidly separated, before and after dephosphorylation, by reversed-phase high-performance liquid chromatography on a styrene 250 column under alkaline conditions. Partial sequencing of the peptides by automated Edman degradation revealed that the serine-115 residue located in the main encephalitogenic determinant of the protein was a phosphorylation site, in addition to the two phosphorylation sites established (threonine-34 and serine-55).     

Selective monofluorination of diols using DFMBA

Selective monofluorination of 1,2- and 1,3-diols was achieved by reaction with DFMBA. The method is applicable for the synthesis of optically-active fluorohydrin derivatives.     

Additivity of electron correlation energy and the ab initio MO calculation of (0–0) S1←S0 transition energies: polychlorinated dibenzofurans

The energies of the S₀ and S₁ states of polychlorinated dibenzofurans (PCDFs) were calculated using the Hartree–Fock (HF) and configuration interaction-singles (CIS) methods. We can obtain the (0–0) transition energies of PCDFs with good accuracy if the energies calculated using the HF and CIS methods are adjusted to take the electron correlation energy into account. The correlation energy of the S₀ state was calculated using the Møller–Plesset correlation correction truncated at the second order (MP2), and that of the S₁ state was determined using experimental data. The correlation energies for both S₀ and S₁ states were expressed as the sum of the contributions arising from dibenzofuran (DF) and substituted chlorine atoms. The energy of the ground state calculated using the additivity approximation was in good agreement with the energy given directly by the MP2 method. The (0–0) S₁←S₀ transition energies corrected for electron correlation energy agreed well with the available experimental data. The approach proposed in this paper may be useful for the estimation of the electronic transition energy for large aromatic molecules.     

High-pressure synthesis and structural characterization of three new polyphosphides, α-SrP3, BaP8, and LaP5

Three novel metal polyphosphides, α-SrP₃, BaP₈, and LaP₅, were prepared in BN crucibles by the reaction of the respective stoichiometric mixtures under a high pressure of 3 GPa at 950-1000°C. Their crystal structures were determined from single-crystal X-ray data (α-SrP₃: space group C2/m, a=9.199(6) Å, b=7.288(3) Å, c=5.690(3) Å, β=113.45(4)°, Z=4, R₁/wR₂=0.0684/0.1180 for 471 observed reflections and 22 variables; BaP₈: space group P−1, a=6.762(2) Å, b=7.233(2) Å, c=8.567(2) Å, α=86.32(2)°, β=84.31(2)°, γ=70.40(2)°, Z=2, R₁/wR₂=0.0476/0.1255 for 2702 observed reflections and 82 variables; LaP₅: space group P2₁/m, a=4.885(1) Å, b=9.673(3) Å, c=5.577(2) Å, β=105.32(2)°, Z=2, R₁/wR₂=0.0391/0.1034 for 1272 observed reflections and 31 variables). α-SrP₃ is isostructural with SrAs₃ and the crystal structure consists of two-dimensional puckered polyanionic layers _∞²[P₃]²⁻ that stack along the c-axis yielding channels occupied by Sr²⁺ counterions. BaP₈ crystallizes in a new structure type which contains a three-dimensional infinite polyanionic framework _∞³[P₃]²⁻, with large channels hosting the barium cations. LaP₅ is a layered compound containing _∞²[P₅]³⁻ polyanionic layers separated by La³⁺ ions. All three compounds exhibit expected diamagnetic behaviors.     

Convenient construction of a variety of glycosidic linkages using a universal glucosyl donor

This letter deals with the concept of constructing four types (cis-α, trans-α, cis-β, and trans-β) of glycosidic linkages using a universal glucosyl donor. The selectively protected universal glucosyl donor 8 was synthesized in 36% yield from d-glucose (eight steps). The donor 8 undergoes glycosidation with a primary carbohydrate alcohol 7 to give disaccharide 9 having a 1,2-cis-α-glycosidic linkage in 90% yield. The construction of the corresponding 1,2-trans-α-glycosidic linkage was performed in 68% yield (three steps) from 9. A similar glycosidation of the 2-O-(N-phenylcarbamoyl)-glucosyl donor 6 derived from 8 with 7 gave disaccharide 11 having a 1,2-trans-β-glycosidic linkage in 75% yield. The construction of the corresponding 1,2-cis-β-linkage was performed in 53% yield (three steps) from 11.     

Simple flow-injection system for the simultaneous determination of nitrite and nitrate in water samples

A novel spectrophotometric reaction system was developed for the determination of nitrite as well as nitrate in water samples, and was applied to a flow-injection analysis (FIA). The spectrophotometric flow-injection system coupled with a copperised cadmium reductor column was proposed. The detection was based on the nitrosation reaction between nitrite ion and phloroglucinol (1,3,5-trihydroxybenzene), a commercially available phenolic compound. Sample injected into a carrier stream was split into two streams at the Y-shaped connector. One of the streams merged directly and reacted with the reagent stream: nitrite ion in the samples was detected. The other stream was passed through the copperised cadmium reductor column, where the reduction of nitrate to nitrite occurred, and the sample zone was then mixed with the reagent stream and passed through the detector: the sum of nitrate and nitrite was detected. The optimised conditions allow a linear calibration range of 0.03–0.30 μg NO₂⁻-N ml⁻¹ and 0.10–1.00 μg NO₃⁻-N ml⁻¹. The detection limits for nitrite and nitrate, defined as three times the standard deviation of measured blanks are 2.9 ng NO₂⁻-N ml⁻¹ and 2.3 ng NO₃⁻-N ml⁻¹, respectively. Up to 20 samples can be analyzed per hour with a relative standard deviation of less than 1.5%. The proposed method could be applied successfully to the simultaneous determination of nitrite and nitrate in water samples.     

Total synthesis of the antitumor acetogenin mosin B: desymmetrization approach to the stereodivergent synthesis of threo/trans/erythro-type acetogenins

A total synthesis of the threo/trans/erythro-type acetogenin mosin B and one of its diastereomers has been achieved. The carbon skeleton is assembled in a convergent fashion from two segments (a THF ring segment and a gamma-lactone segment) through the Nozaki-Hiyama-Kishi reaction. The THF ring segment was stereoselectively constructed by a stereodivergent synthesis starting from a common intermediate (4-cyclohexene-1,2-diol) based on a desymmetrization strategy. The gamma-lactone segment was synthesized by coupling a triflate and a chiral alpha-sulfenyl gamma-lactone. By virtue of these synthetic results, we suggest that the absolute configuration of natural mosin B is 1 a. Antiproliferative effects of 1 a and 1 b were also investigated.     

Fluorimetric determination of nitrate in natural waters with 3-amino-1,5-naphthalenedisulphonic acid in a flow-injection system

A rapid, sensitive and precise flow-injection method for the determination of nitrate in natural waters is presented. Nitrate is first reduced in a copperized cadmium column to nitrite, which reacts with 3-amino-1,5-naphthalenedisulphonic acid to form the azoic acid. This acid forms a fluorescent salt in alkaline medium. The injecton rate is about 30 h^?1, the relative standard deviation for 10 injections of 2 × 10^?5 M nitrate is 0.8%, and the detection limit (S/N = 3)_is 1 × 10^?8 M nitrate.