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471.
A synthetic methodology for the synthesis of alpha-amino acid precursors directly from the corresponding aldehydes using N,O-dialkylated hydroxylamines and masked acyl cyanide (MAC) reagents was developed. The one-pot reaction can be carried out under mild conditions and without a separate purification step of the imino species. The method was applied to the synthesis of optically pure (+)-4-methylphenylglycine and the derivatives by using an Abiko-Masamune's tricyclic 1,2-oxazolidine as the chiral auxiliary. 相似文献
472.
An illustrious complex [Fe(ptz)6](BF4)2 (ptz = 1-propyl-tetrazole) (1) which was produced in the form of submicron crystals and thin film on Allium cepa membrane was probed by 57Fe Mossbauer spectroscopy in order to follow its intrinsic spin crossover. In addition to a weak signal that corresponds to neat SCO compound significant amount of other iron compounds are found that could have morphed from 1 due to specific host-guest interaction on the lipid-bilayer of bio-membrane. Further complimentary information about biogenic role of membrane, was obtained from variable temperature Mossbauer spectroscopy on a ~5% enriched [57Fe(H2O)6](BF4)2 salt on this membrane. 相似文献
473.
Hisao Takeuchi 《Macromolecular theory and simulations》1999,8(4):391-401
The exchange kinetics of polymers adsorbing on a solid surface is extensively studied by dynamic Monte Carlo simulations. A model employed simulates a semidilute polymer solution placed in contact with a solid surface that attracts polymer segments by the adsorption interaction (χs). The exchange process of polymer chains, between the solution and the adsorbed polymer layer, is examined under various conditions. The exchange kinetics shows two characteristic regimes with increasing chain length. One is the diffusion‐controlled regime found with a small χs , and the other the detachment‐controlled regime with a large χs . These two regimes are well described by a kinetic theory. Various dynamic quantities show that the diffusion‐controlled regime is not due to sluggish dynamics near the surface, but rather to bulk diffusion of chains. The diffusion‐controlled regime found in this study is considered to appear at the high temperature limit. 相似文献