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71.
Allylation of acetals with allylsilanes is catalyzed by iodotrimethylsilane to give the corresponding homoallyl ethers, with regiospecific transposition of the allyl group. 相似文献
72.
Diversity-oriented organic synthesis (DOS) is a key concept for construction of skeletally diverse small molecule libraries to discover drug-like small molecules. Here, we describe a DOS class to transform a complex 7-oxanorbornene skeleton, which is readily accessible by a tandem Ugi/Diels-Alder reaction, into two heterotricycle skeletons selectively by using tandem ROM/CM/RCM reaction. In the present study, the mode of cyclization is pre-encoded by building blocks used in the complexity-generating tandem Ugi/Diels-Alder reaction. Since variable alkenes can be used in the CM reaction, our approach can be extended to construct both skeleton- and appendage-diverse small molecule libraries. 相似文献
73.
Bando T Narita A Sasaki S Sugiyama H 《Journal of the American Chemical Society》2005,127(40):13890-13895
We examined DNA alkylation by pyrrole (Py)-imidazole (Im) hairpin polyamides, which possess 1,2,9,9a-tetrahydrocyclopropa[1,2-c]benz[1,2-e]indol-4-one (CBI) or cyclopropapyrroloindole (CPI) as DNA alkylating moieties. High-resolution denaturing gel electrophoresis revealed that alkylation by CBI conjugates 2 and 4 occurred specifically at adenines (A) in matched sequences, whereas CPI conjugates 1 and 3 alkylated both A and guanines (G) in matched sequences. The origin of the different reactivity of CBI and CPI conjugates is discussed in relation to the electrophilicity of the cyclopropane moiety. The high selectivity of the CBI conjugate gives additional sequence specificity relative to CPI conjugates that would be useful for the biological applications. 相似文献
74.
Shimizu H Tada N Ikawa R Kume T Sasaki S 《The journal of physical chemistry. B》2005,109(47):22285-22289
Visual observations through a microscope and in situ Raman measurements have been made for single crystalline ethylene hydrate (EH) and binary methane-ethylene hydrate (MEH) at pressures up to 3.7 GPa and room temperature. Both hydrates showed pressure-induced phase transitions at 1.6, 2.0, and 3.0 GPa for EH and at 1.7, 2.1, and 3.3 GPa for MEH. The cubic sI phase of EH and MEH remains stable up to 1.6 and 1.7 GPa, respectively, which are more widely ranging values than the values for the methane hydrate sI phase. In this sI phase of binary MEH, the cage occupancies by methane and ethylene molecules are investigated from Raman spectra. Above P = 3.0 GPa for EH and 3.3 GPa for MEH, they decomposed by associating with the formation of the polyethylene. 相似文献
75.
Yasuo Shimano Shoichi Sasaki 《Journal of polymer science. Part A, Polymer chemistry》1983,21(5):1331-1345
Reaction of sulfinylaminobenzoyl chlorides with lead thiocyanate gave sulfinylaminobenzoyl isothiocyanates (SBIs), from which were derived aminobenzoyl isothiocyanate hydrochlorides (ABIHs). AB polyacylthioureas (PATUs) with inherent viscosities of up to 0.28 dL/g were obtained by treating the SBI with an equivalent of water in N-methyl-2-pyrrolidone (NMP). Low-temperature solution polyaddition of the ABIH afforded AB PATU with inherent viscosities of up to 0.66 dL/g, which were further increased to as high as 0.75 dL/g by adding lithium bases to the polymerization mixtures. Polyaddition of isophthaloyl diisothiocyanate with intermediate diamines formed by hydrolyzing the adducts of SBI and aromatic diamines afforded copolyacylthioureas with inherent viscosities of up to 1.15dL/g. The copolymers were generally soluble in NMP, whereas solubilities of the AB PATU in analogous solvents were relatively low. Thermogravimetric analyses in both air and nitrogen exhibited weight losses of 5% at 204–236°C for AB PATU and at 170–192°C for the copolymers. 相似文献
76.
Here, we report a diversity-oriented synthetic approach toward skeletally diverse, cyclized peptidomimetics with diverse appendages. Starting from α-(N-acylamino)amides with various appendages, 12 to 16-membered lactams with defined olefin geometry were synthesized by a common synthetic sequence. We also synthesized the macrocycle in a liquid phase directed toward a construction of the peptidomimetics library. 相似文献
77.
78.
Computer-aided structure elucidation methodology is discussed. Major processes involved in computer-aided structure elucidation systems are partial-structure elucidation, structure generation, and structure examination. For the three representative systems CONGEN, CASE, and CHEMICS, these processes are examined. There are four necessary conditions for automated chemical structure elucidation systems: reliability, width of application, ease of modification and portability. 相似文献
79.
Katsuhiko Tomooka Nobuyuki Komine Tomoya Sasaki Hideo Shimizu Takeshi Nakai 《Tetrahedron letters》1998,39(52):2362-9718
Treatment of (E)-6-phenyl-5-hexenyl carbamates with s-BuLi/(−)-sparteine is shown to afford the trans-1,2-disubstituted cyclopentane derivatives in high % ee, along with the bicyclo[3.1.0]hexanes (bicyclization products). 相似文献
80.
Kazunori Takada Hiroya Sakurai Fujio Izumi Takayoshi Sasaki 《Journal of solid state chemistry》2004,177(1):372-376
Monolayer hydrate (MLH) NaxCoO2·y′H2O was obtained from superconducting bilayer hydrate (BLH) NaxCoO2·yH2O by partial extraction of H2O molecules between the CoO2 layers. Magnetization measurements indicated that electron densities in the CoO2 layer of the MLH phase remained unchanged after the water extraction. Nevertheless, superconductivity was completely suppressed in the MLH phase. This strongly suggests that the highly 2D nature in the BLH phase due to its thick insulating layers consisting of H2O molecules and Na+ ions plays an important role for inducing superconductivity. 相似文献