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Using regioselective cuprations (via magnesiations), various primary, secondary and tertiary aminated pyrimidine and purine derivatives were prepared by the oxidative coupling of lithium amidocuprates using chloranil. DNA and RNA units such as aminated uracil or thymine, and adenine, as well as a CDK inhibitor, purvalanol A, were all obtained under mild conditions and satisfactory yields. 相似文献
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Enantioselective conjugate radical addition to 2‐acyloxymethyl cycloalkenones proceeds in high yield with outstanding diastereoselectivity and excellent enantioselectivity using chiral salen Lewis acids. The process provides access to 2,3‐disubstituted cycloalkanones, a structural motif present in natural products. 相似文献
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A simple and efficient protocol for the preparation of 7-substituted purines is described. 6- and 2,6-Dihalopurines were N(9)-tritylated and then transformed to 7,8-dihydropurines by DIBAL-H. Subsequent N(7)-alkylation followed by N(9)-trityl deprotection with trifluoroacetic acid was accompanied by spontaneous reoxidation, which led to the 7-substituted purines at 55-88% overall isolated yields. 相似文献
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[reaction: see text]. An efficient and general route to the soluble polymer-assisted synthesis of a set of 14 different N-substituted pyrroles using dendritic polyglycerol as a high-loading support is presented. The transformation of furan to the key intermediate 2,5-dialkoxytetrahydrofuran was performed by electrochemical oxidation followed by catalytic hydrogenation with Pt/C in high yield. Both reactions required heterogeneous reagents which can be conveniently used with polyglycerol as a soluble support. 相似文献
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We have measured the temperature dependences of the conductance G and the dielectric permittivity ε′ of the (TMTTF)2SbF6 compound under a moderate pressure. The maximum of G(T) associated with the Mott-Hubbard localization disappears under pressure. With increasing pressure the peak in ε′(T), corresponding to the charge ordering (CO) phase transition, shifts to lower temperatures and broadens. At pressures above 0.24 GPa, ε′(T) becomes strongly frequency dependent. These modifications are explained in the frame of the extended Hubbard model and a slowing down behavior. 相似文献
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ABSTRACT The synthesis and the amphiphilic properties of 1-glycosyl-2-acylhydrazines are described. This new class of surfactants, referred to as glycosylhydrazides, is easily available from a reducing sugar and hydrazides without protection. Seven hydrazides having an alkyl chain of up to fourteen carbon atoms, are coupled with glucose giving 1-glucosyl-2-acylhydrazines in good yields; 1-maltosyl-2-octanoylhydrazine, as a typical disaccharide-based surfactant, is prepared as well. Critical micellar concentrations of these surfactants range from 0.04 to 252 mM. 相似文献
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A well-formed energy gap Δ is observed in the energy spectrum of the quasi-one-dimensional orthorhombic conductor TaS3 at temperatures much lower than the Peierls transition temperature T
P
. As the temperature increases, in the region T>T
P
/2 there is a growth of the density of states in the gap and a relative decrease of the density at energies greater than Δ.
In addition, absorption lines which probably correspond to soliton states in a charge-density wave are observed in the gap.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 4, 246–250 (25 February 1996) 相似文献