Synthetic Studies on Sialoglycoconjugates 45: Synthesis of 1-Deoxynojirimycin-Containing Oligosaccharides Related to the Cancer-Associated Sialyl-Lewis a Antigen Recognized by Lec-Cams (Selectins)

Abstract

Sialyl-Lewis a (sLe^a), mainly expressed on cancer cells of the digestive organs,² has been known as an important cancer-associated carbohydrate antigen.³ Very recently, it has been demonstrated^4–9 that the (sLe^a) antigen is one of the possible ligands recognized by selectins, a family of lectin-type cell adhesion molecules (LEC-CAMS). These findings suggest that the (sLe^a) antigen may be involved in the process of hematogeneous metastasis of cancer cells. 1-Deoxynojirimycin (DNJ) and related compounds have been shown¹⁰ not only to be potent inhibitors of a-glycosidases and glycoprotein-processing enzymes, but also to be of potential clinical value as antidiabetic, antineoplastic and anti-HIV agents. In a preceding paper we reported the synthesis of DNJ-containing sialyl-Lewis x antigen which has been identified as a major carbohydrate ligand for leukocyte adhesion on vascular endothelium mediated by selectins. The present paper describes the first synthesis of l-deoxynojirimycin- containing cancer-associated (sLe^a) antigen and related compounds.     

Structure Determination and Total Synthesis of (+)‐16‐Hydroxy‐16,22‐dihydroapparicine

Herein, we describe the first asymmetric total synthesis and determination of the relative and absolute stereochemistry of naturally occurring 16‐hydroxy‐16,22‐dihydroapparicine. The key steps include 1) a novel phosphinimine‐mediated cascade reaction to construct the unique 1‐azabicyclo[4.2.2]decane core, including a pseudo‐aminal‐type moiety; 2) a highly stereospecific 1,2‐addition of 2‐acylindole or a methylketone through a Felkin–Anh transition state for the construction of a tetrasubstituted carbon center; and 3) an intramolecular chirality‐transferring Michael reaction of the ketoester, with neighboring‐group participation, to introduce a chiral center at C15 in the target molecule. In addition, we evaluated the antimalarial activity of synthetic (+)‐(15S,16R)‐16‐hydroxy‐16,22‐dihydroapparicine and its intermediate against chloroquine‐resistant Plasmodium falciparum (K1 strain) parasites.     

Probing the Reorganization of Ionic Liquids’ Structure Induced by CO2 Sorption

The sorption of CO₂ is often used to modify the macroscopic properties of liquids and solids. In the particular case of ionic liquids, different from molecular liquids, the sorption of CO₂ may not induce volume expansions due to the strong Coulombic interactions between the ions of the fluid. However, a considerable viscosity decrease has been systematically observed. In order to understand the mechanisms of properties modifications in ionic fluids, herein we used Raman spectroscopy to probe the effect of CO₂ on the structure of ionic liquids. It is shown that CO₂ perturbs the electrostatic interactions between cations and anions, thus inducing a change in the polar domain of ionic liquids. It is observed that ionic liquids having bulkier ions are more prone to be perturbed by CO₂ in comparison to ionic liquids having smaller ions. These results reveal new means of controlling the electrostatic forces between the ions and contributes to the mechanistic understanding of the modification of the macroscopic properties of ionic liquids by CO₂ sorption.     

Band‐Edge Luminescence from Oxide and Halide Perovskite Semiconductors

Because perovskite crystals exhibit unique magnetic, conductive, and optical properties, they have been the subject of many fundamental investigations in various research fields. However, investigations related to their use as optoelectronic device materials are still in their early days. Regarding oxide perovskites, which have been investigated for a long time, the efficiency of photoluminescence (PL) induced by band‐to‐band transitions is extremely low because of the localized nature of the carriers in these materials. On the other hand, halide perovskites exhibit a highly efficient band‐edge PL attributable to the recombination of delocalized photocarriers. Therefore, it is expected that this class of high‐quality materials will be advantageous for optoelectronic devices such as solar cells and light‐emitting diodes. In this Minireview, we discuss various aspects of the PL properties and carrier dynamics of SrTiO₃ and CH₃NH₃PbX₃ (X=I, Br), which are representative oxide and halide perovskites.     

Gelation properties of poly(aryl ether)dendrons bearing long alkyl chains

Poly(aryl ether) dendrons (2) bearing long alkyl chains can undergo physical gelation in various organic solvents, especially alkanes and alcoholic solvents. In contrast, 3,4,5-trialkoxyphenyl derivatives (1), which are the building blocks of the dendrons (2), do not exhibit any gelation properties; thus, revealing the key role of the dendron structure in the aggregation/gelation process. Hansen solubility parameters allow us to gain a detailed understanding of the role of solvent in gelation. Critical gel concentrations, FT-IR spectroscopy, NMR spectroscopy, T _gel measurements, and scanning electron microscopy are used to characterize the gel structures.     

Transformimidoylation of 1-(N-Alkyliminoformyl) Imidazole with Amino Acid

In our preceeding paper,¹ we described a new synthetic method of reactive 1-(N-alkyliminoformyl)azoles (1) and the transfer of formimidoyl group (transformimidoylation) of 1 with amine, alcohol and the so-called active methylene compounds.     

Radioprotection by DMSO in nitrogen-saturated mammalian cells exposed to helium ion beams

The contribution of OH radical-mediated indirect action by particle beams under hypoxic irradiation condition was investigated by using a radical scavenger. V79 cells were irradiated with 150 MeV/nucleon helium ions at an LET of 2.2 keV/μm in the presence or absence of DMSO, and their colony survivals were determined. The contribution of indirect action to cell killing under hypoxic condition was estimated to be 52±9%. We conclude that OH radical-mediated indirect action still has a half in total contribution on cell killing under hypoxic condition.     

Raman spectroscopy of a sulfur dioxide visual sensor: The origin of the two colors in the solid sample

The vibrational spectroscopic characterization of a sulfur dioxide visual sensor was carried out using a Raman microscope system. It was observed the formation of two distinct complexes, that were characterized by the position and relative intensities of the bands assigned to the symmetric stretching, ν_s(SO₂), of the linked SO₂ molecules. In fact, in the yellowish orange complex, that corresponds to the 1:1 stoichiometry, only one band is observed, assigned to ν_s(SO₂) at ca. 1080 cm^?1 and, in the deep red complex, that corresponds to the 1:2 complex, at ca. 1070 and 1090 cm^?1 are observed. The variation of the relative intensities of the bands assigned to ν_s(SO₂) present in the Ni(II)·SO₂ complex, in different points of the sample, shows clearly the requirement of the Raman microscope in the vibrational characterization of this kind of molecular sensor.     

Enantioselective alkynylation of aldehydes with chiral β-imino α-perfluoroalkylpropanol derivatives

Chiral β-imino α-perfluoroalkylpropanol derivatives 1 were prepared by condensation of (2S,3S)-2-amino-3-perfluorooctyl-1-phenylpropan-3-ol 2 and aldehydes. Among them, (2S,3S)-1d prepared from 2 and salicylaldehyde catalyzed the asymmetric alkynylation of aldehydes using alkynylzincs to afford the product in up to 81% ee.     

Precise and fast secondary ion mass spectrometry depth profiling of polymer materials with large Ar cluster ion beams

We demonstrate depth profiling of polymer materials by using large argon (Ar) cluster ion beams. In general, depth profiling with secondary ion mass spectrometry (SIMS) presents serious problems in organic materials, because the primary keV atomic ion beams often damage them and the molecular ion yields decrease with increasing incident ion fluence. Recently, we have found reduced damage of organic materials during sputtering with large gas cluster ions, and reported on the unique secondary ion emission of organic materials. Secondary ions from the polymer films were measured with a linear type time‐of‐flight (TOF) technique; the films were also etched with large Ar cluster ion beams. The mean cluster size of the primary ion beams was Ar₇₀₀ and incident energy was 5.5 keV. Although the primary ion fluence exceeded the static SIMS limit, the molecular ion intensities from the polymer films remained constant, indicating that irradiation with large Ar cluster ion beams rarely leads to damage accumulation on the surface of the films, and this characteristic is excellently suitable for SIMS depth profiling of organic materials. Copyright © 2009 John Wiley & Sons, Ltd.