Conformational transition of the core chain in radiation-modified polysilane micelles formed in selective solvents

Poly(methyl acrylate)-grafted poly(methyl-n-propylsilane) (PMPrS-g-PMA) and poly(acrylic acid)-grafted PMPrS (PMPrS-g-PAA) were synthesized by gamma-ray-induced graft polymerization, and the association behavior of these graft copolymers was investigated in selective solvents composed of good and poor solvents for the PMPrS main chain. Fluorescence spectroscopy with perylene as a fluorescent probe revealed that PMPrS-g-PAA in a water/THF mixed solvent self-assembles into micelles with a swollen core of PMPrS chains in the water content range of 50-95%. UV spectroscopy demonstrated that a further increase of the water content gives rise to the conformational transition of the PMPrS chains in the micelle core from the random conformation to the conformation that corresponds to that in the solid state at a water content of ca. 95%, independent of the grafting yield. Similar behavior was also observed in DMSO/THF solutions of PMPrS-g-PMA, for which the conformational transition occurred at the constant DMSO content of ca. 95%. These results indicate that solvatochromic behavior of polysilane, which is a characteristic feature of polysilane, proved to provide information on the inner structure of those micelles: PMPrS chains in the core undergo conformational transition as the content of the poor solvents for PMPrS increases, while maintaining the micelle structure.     

Novel Chiral Building Block: (2R,3S)-2-(1,3-Dithian-2-yl)-3-hydroxybutanoates. Highly Diastereo- and Enantioselective Baker's Yeast Reduction of 2-(1,3-Dithian-2-yl)-3-oxobutanoates

The baker's yeast reduction of 2-(1,3-dithian-2-yl)-3-oxobutanoates gave (2R,3S)-2-(1,3-dithian-2-yl)-3-hydroxybutanoates in good yiels and in high diastereo- and enantioselectivity.     

Synthesis and structure revision of tyroscherin, and bioactivities of its stereoisomers against IGF-1-dependent tumor cells

Synthesis of the proposed structure of tyroscherin, a growth inhibitor of IGF-1-dependent cancer cells, was succeeded by one-pot Julia coupling. However, spectral data of the synthetic compound were not identical with those of natural tyroscherin. The stereochemistry of tyroscherin is revised to be 2S,3R,8R,10R by syntheses of stereoisomers. Synthetic tyroscherin showed more potent activity than its stereoisomers against IGF-1-dependent cancer cells.     

A Click-Chemistry Linked 2′3′-cGAMP Analogue

2′3′-cGAMP is an uncanonical cyclic dinucleotide where one A and one G base are connected via a 3′-5′ and a unique 2′-5′ linkage. The molecule is produced by the cyclase cGAS in response to cytosolic DNA binding. cGAMP activates STING and hence one of the most powerful pathways of innate immunity. cGAMP analogues with uncharged linkages that feature better cellular penetrability are currently highly desired. Here, the synthesis of a cGAMP analogue with one amide and one triazole linkage is reported. The molecule is best prepared via a first Cu^I-catalyzed click reaction, which establishes the triazole, while the cyclization is achieved by macrolactamization.     

A remark on the normalization of the standard zeta values for Siegel modular forms

In (Katsurada in Math. Z. 259:97–111, 2008), we gave a certain type of normalization of the standard zeta values for Siegel modular forms, and considered the relationship between such values and congruence of cuspidal Hecke eigenforms. In this paper we give more reasonable normalization for such values and improve our previous result.     

Growth of polar axis oriented tetragonal Pb(Zr,Ti)O3 films on CaF2 substrates with transparent (La0.07Sr0.93)SnO3

Epitaxial (La_0.07Sr_0.93)SnO₃ [LSSO] films were deposited on CaF₂ substrates by pulse laser deposition. The (1 0 0)_c orientation of LSSO films was observed only on (1 1 0)CaF₂, whereas (1 1 0)_c orientation was found on (1 1 1)CaF₂ and (1 0 0)CaF₂. (0 0 1) polar axis oriented tetragonal Pb(Zr_0.35Ti_0.65)O₃ films were grown on the fabricated (1 0 0)_cLSSO∥(1 1 0)CaF₂ by pulsed metal organic chemical vapor deposition. The (0 0 1)Pb(Zr_0.35Ti_0.65)O₃∥(1 0 0)cLSSO∥(1 1 0)CaF₂ stack structure exhibited about 70% transparency with an adsorption edge of approximately 330 nm.     

Hypersequent calculi for intuitionistic logic with classical atoms

We discuss a propositional logic which combines classical reasoning with constructive reasoning, i.e., intuitionistic logic augmented with a class of propositional variables for which we postulate the decidability property. We call it intuitionistic logic with classical atoms. We introduce two hypersequent calculi for this logic. Our main results presented here are cut-elimination with the subformula property for the calculi. As corollaries, we show decidability, an extended form of the disjunction property, the existence of embedding into an intuitionistic modal logic and a partial form of interpolation.     

Oxovanadium(v)-catalyzed oxidative biaryl synthesis from organoborate under O2

Oxidative ligand coupling of organoborates was catalyzed by VO(OEt)Cl(2) under oxygen atmosphere, which provides a versatile method for the selective synthesis of symmetrical or unsymmetrical biaryls.