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21.
A new, simple strategy has been formulated for the synthesis of deoxyamino sugars from a non-sugar starting material. Starting from the enantiomerically pure diol obtained from ethyl sorbate by Sharpless asymmetric dihydroxylation, the synthesis of two types of 2,3,4,6-tetradeoxy-4-amino sugars—d-tolyposamine and 4-epi-d-tolyposamine—, and formal synthesis of 2,4,6-trideoxy-4-amino sugar—d-vicenisamine—were performed. 相似文献
22.
The zero-field 153Eu NMR in EuSe has been observed as a function of the pressure up to 14 kbar in the temperature range between 1.7 and 4.2 K. A sequent magnetic phase transition of NSNS-NNS-NNSS-NNN occurs with pressure at 1.7 K. In the NNSS state (2.0 ? P ? 4.8 kbar) the NMR frequency v is insensitive to the pressure. In the ferromagnetic state (P ? 4.8 kbar) v depends remarkably on the pressure, and the exchange interaction between the nearest Eu neighbours J1 is shown to increase rapidly with decreasing the Eu-Eu distance. The pressure dependences of the Eu hyperfine field suggest that the magnetic moment of a Eu2+ ion in the ferromagnetic state under pressure is smaller than the ideal saturation value at 0 K. 相似文献
23.
The temperature dependence of the electrical conductivity of magnetite was measured under hydrostatic pressure up to 18.4 kbar. It is found that the temperature of the conductivity maximum in the high temperature phase is more rapidly reduced by pressure (dTm/dP = -4.1 K/kbar) than the Verwey temperature (dTv/dP = -0.27 K/kbar). The discontinuous change of the conductivity at Tv appears to increase with applied pressure as a result of a lowering of Tm. 相似文献
24.
[structure: see text] Mixing oligothiophenes and polysaccharides, such as amylose and schizophyllan, affords novel inclusion complexes, in which oligothiophene guests adopt twisted conformation in the chiral channel created by left- or right-handed helical wrapping with the polysaccharide host polymers, leading to optical activity. 相似文献
25.
Hironori Okamura Takanobu Fujioka Naoki Mori Tohru Taniguchi Kenji Monde Hidenori Watanabe Hirosato Takikawa 《Tetrahedron letters》2019,60(32):150917
Salinipostins are cyclic enol-phosphotriesters isolated from a marine-derived Salinispora sp. as antimalarial compounds. Herein, the first enantioselective synthesis of salinipostin A was achieved. Organocatalyst-mediated asymmetric cyclopropanation and regioselective cyclopropane ring opening were the key steps. 相似文献
26.
We report what are believed to be the first measurements of the phase sensitivity of a fiber sensor array using multiple low-gain remotely pumped amplifiers with an interferometric sensor inserted. The measured phase sensitivities for individual rungs average 5.7 microrad(rms)/ radicalHz and exhibit no dependence on rung number, in agreement with predictions. 相似文献
27.
The base-mediated intramolecular cyclization reaction of 2-alkynylphenylphosphine oxides affords benzo[ b]phosphole oxides, which show intense blue-green fluorescence. Benzo[ b]phospholes are also prepared by the reduction of benzo[ b]phosphole oxides. 相似文献
28.
Takanobu Hara 《Potential Analysis》2016,44(1):189-214
We consider divergence form elliptic equations with a strongly singular drift term ?d i v(A?u)+b??u=μ in a domain \({\Omega } \subset \mathbb {R}^{n}\) (n≥3). We give a weak-type \(L^{1} - L^{n / (n - 2), \infty }\) estimate for a solution to the Dirichlet problem with homogeneous boundary condition. Moreover, we give a two-sided pointwise potential estimate for a weak solution and its applications. 相似文献
29.
Takanobu Hara 《manuscripta mathematica》2016,149(1-2):45-62
In this note, we obtain sharp bounds for the Green’s function of the linearized Monge–Ampère operators associated to convex functions with either Hessian determinant bounded away from zero and infinity or Monge–Ampère measure satisfying a doubling condition. Our result is an affine invariant version of the classical result of Littman–Stampacchia–Weinberger for uniformly elliptic operators in divergence form. We also obtain the L p integrability for the gradient of the Green’s function in two dimensions. As an application, we obtain a removable singularity result for the linearized Monge–Ampère equation. 相似文献
30.
Thermolysis of 2,3-benzo-1,4-diphenyl-7-silanorbornadiene derivatives 1 in the presence of 2,3-dimethylbutadienes gave the trapping products of the corresponding bissilylene, disilenylsilylene, and a tetrasila-1,3-butadiene, via a consecutive disilanylsilylene to silyldisilene rearrangement. 相似文献