A Photoinduced,Nickel-Catalyzed Reaction for the Stereoselective Assembly of C-Linked Glycosides and Glycopeptides

C-Alkyl glycosides and glycoproteins exist in natural products and are prized for their role as carbohydrate mimics in drug design. However, a practical strategy that merges glycosyl donors with readily accessible reagents, derived from abundant carboxylic acid and amine feedstocks, is yet to be conceived. Herein, we show that a nickel catalyst promotes C−C coupling between glycosyl halides and aliphatic acids or primary amines (converted into redox-active electrophiles in one step), in the presence of Hantzsch ester and LiI (or Et₃N) under blue LED illumination to deliver C-alkyl glycosides with high diastereoselectivity. Mechanistic studies support the photoinduced formation of alkyl radicals that react with a glycosyl nickel species generated in situ to facilitate cross-coupling. Through this manifold, innate CO₂H and NH₂ motifs embedded within amino acids and oligopeptides are selectively capped and functionalized to afford glycopeptide conjugates through late-stage glycosylation.     

Synthesis and Structural Analysis of Organic Cyclic Polyselenides Obtained from the Reaction of a Bissilylcarbenoid with Selenium

The synthesis and isolation of the first examples of a tetraselenolane and a hexaselenepane, obtained from the reaction of a bissilylcarbenoid (R^Si₂CBrLi; R^Si=SiMePh₂) with elemental selenium, is reported. The molecular structures of these cyclic polyselenides were determined using single-crystal X-ray diffraction analysis. The selective synthesis of these polyselenides was achieved by controlling the reaction temperature. Stoichiometric deselenation of the hexaselenepane with triphenylphosphine afforded the corresponding tetraselenolane in quantitative yield. Further deselenation of the tetraselenolane with excess triphenylphosphine did not furnish the expected selenoketone but the diselenirane, as confirmed by spectroscopic analysis.     

Structural factors controlling tensile yield deformation of semi‐crystalline polymers

In this work, a molecular model is proposed to account for the stress‐strain relationships of spherulitic polymers. To describe the yielding behavior of spherulitic polymers, we introduced a new structural unit, i.e. the lamellar cluster, which is represented by several stacked lamellae bound by some tie molecules. It was shown that the tie molecules between the adjacent lamellar clusters produce the concentrated load acting on the cluster surface, leading to bending deformation of the lamellar cluster. The yielding behavior was explained by the disintegration of lamellar cluster due to the bending deformation.     

Crystal Structure Study of Co(II) Complexes with 2,2′-(1,4-Ethylenedioxyl) Dibenzoic Acid-[Co · L · (H2O)3]n · nH2O· 0.2 nH2O

The structure ofS the title complex [Co. L. (H₂O)₃]_n. nH₂O. 0.2 nH₂O has been established by single crystal X-ray diffraction. Crystals of the complex are monoclinic, space group C2/c with cell constants α = 45.29(4), b=10.631(6), c = 8.015(6) Å, β = 90.65(8)°, Z = 8, D_c = 1.489 g. cm⁻³ The structure was solved and refined to R =0.0478 (wR = 0.0577). In the chain structure, Co(II) ions are hexacoordinated by 0 atoms in an octahedral arrangement. CoO₆ octahedra share corners (bridged) through O atoms of water, with each L^2--ligand binding two adjacent Co atoms.     

Si1-xGex Mixed Crystals Grown by Pulling-Down Technique with Multi-Capillary Channels

Si_1-xGe_x mixed crystals with 5 at% Ge concentration have been grown by the pulling-down technique using a crucible with multi-capillary channels. The unique feature of the technique is that Ge solute concentration of the small molten zone is maintained constant due to the condition of no back diffusion of solute through the capillary channels, and that the diffusion-controlled solute transport causes the effective distribution coefficient to be unity. The Ge concentration was measured by the electron probe microanalysis and observed to be homogeneous along both the longitudinal and radial directions. The two-dimensional distribution on the whole cross section was also found to be uniform.