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71.
72.
Pérez-Fernández R Pittelkow M Belenguer AM Sanders JK 《Chemical communications (Cambridge, England)》2008,(15):1738-1740
A two-phase approach to dynamic combinatorial chemistry is described using disulfide exchange chemistry; the use of two phases significantly increases the possibilities and the scope of dynamic combinatorial chemistry by facilitating the combination of otherwise incompatible building blocks. 相似文献
73.
The method of moments is used to show how the structures of molecules and solids is sensitive to the number of valence electrons. 相似文献
74.
75.
Jeremy P. Scott Deborah C. Hammond Elizabeth M. Beck Karel M.J. Brands Antony J. Davies Ulf-H. Dolling Derek J. Kennedy 《Tetrahedron letters》2004,45(17):3345-3348
The efficient preparation of 4-aryl-4-phenylsulfonyl cyclohexanones, containing a quaternary sulfone-bearing carbon centre, is described. Their synthesis proceeds in 38-78% overall yield by way of three steps: (i) sulfinate alkylation; (ii) methylenation; and (iii) regioselective Diels-Alder condensation with 2-trimethylsiloxybutadiene. The scope and limitations of the one-pot Mannich-type methylenation described were examined. 相似文献
76.
Vogensen SB Greenwood JR Varming AR Brehm L Pickering DS Nielsen B Liljefors T Clausen RP Johansen TN Krogsgaard-Larsen P 《Organic & biomolecular chemistry》2004,2(2):206-213
(RS)-3-Hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-5-carboxylic acid (5-HPCA)(), which is a conformationally constrained cyclised analogue of AMPA has previously been described as causing glutamate receptor mediated excitations of spontaneously firing cat spinal interneurons in a similar fashion to AMPA. We have now prepared the enantiomers of through chiral chromatographic resolution of (RS)-3-(carboxymethoxy)-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-5-carboxylic acid () followed by a stereoconservative hydrolysis resulting in the enantiomers of with high enantiomeric excess (% ee [greater-than-or-equal] 99). The absolute configurations indicated by an X-ray analysis of (-)- monohydrate were confirmed by comparing observed and ab initio calculated electronic circular dichroism spectra and by stereoconservative synthesis of (S)- from (S)-AMPA, the pharmacologically active form of AMPA. The pharmacological effects at native and cloned (GluR1-4) AMPA receptors were shown to reside exclusively with (R)-(+)-, in striking contrast to the usual stereoselectivity trend among AMPA receptor agonists. The reasons for this anomalous behaviour became clear upon docking both enantiomers of to the agonist binding site of GluR2. 相似文献
77.
Exact time-dependent wavepacket calculations of helium atom scattering from model symmetric, chiral, and hexagonal surfaces are presented and compared with their classical counterparts. Analysis of the momentum distribution of the scattered wavepacket provides a convenient method to obtain the resulting energy and angle resolved scattering distributions. The classical distributions are characterized by standard rainbow scattering from corrugated surfaces. It is shown that the classical results are closely related to their quantum counterparts and capture the qualitative features appearing therein. Both the quantum and classical distributions are capable of distinguishing between the structures of the three surfaces. 相似文献
78.
We present the use of hydrazone dynamic combinatorial libraries (DCLs) to identify macrocyclic receptors that are selective for alkaline earth metal ions over alkali metal ions. In particular, the toxic heavy metal ions Sr(2+) and Ba(2+) induce characteristic changes in the DCLs. Four macrocycles were isolated and characterised by LCMS, HRMS, NMR and X-ray crystallography; binding studies by UV-Vis spectroscopy confirm the selectivity observed in the DCLs. 相似文献
79.
80.
Synthetic Co(III) complexes containing N5 donor sets undergo glutathionylation to generate biomimetic species of glutathionylcobalamin (GSCbl), an important form of cobalamin (Cbl) found in nature. For this study, a new Co(III) complex was synthesized derived from the polypyridyl pentadentate N5 ligand N4PyCO(2)Me (1). The compound [Co(N4PyCO(2)Me)Cl]Cl(2) (3) was characterized by X-ray crystallography, UV-vis, IR, (1)H NMR, and (13)C NMR spectroscopies and mass spectrometry (HRMS). Reaction of 3 with glutathione (GSH) in H(2)O generates the biomimetic species [Co(N4PyCO(2)Me)(SG)](2+) (5), which was generated in situ and characterized by UV-vis and (1)H NMR spectroscopies and HRMS. (1)H NMR and UV-vis spectroscopic data are consistent with ligation of the cysteine thiolate of GSH to the Co(III) center of 5, as occurs in GSCbl. Kinetic analysis indicated that the substitution of chloride by GS(-) occurs by a second-order process [k(1) = (10.1 ± 0.7) × 10(-2) M(-1) s(-1)]. The observed equilibrium constant for formation of 5 (K(obs) = 870 ± 50 M(-1)) is about 3 orders of magnitude smaller than for GSCbl. Reaction of the Co(III) complex [Co(Bn-CDPy3)Cl]Cl(2) (4) with GSH generates glutathionylated species [Co(Bn-CDPy3)(GS)](2+) (6), analogous to 5. Glutathionylation of 4 occurs at a similar rate [k(2) = (8.4 ± 0.5) × 10(-2) M(-1) s(-1)], and the observed equilibrium constant (K(obs) = 740 ± 47 M(-1)) is slightly smaller than for 5. Glutathionylation showed a significant pH dependence, where rates increased with pH. Taken together, these results suggest that glutathionylation is a general reaction for Co(III) complexes related to Cbl. 相似文献