New phosphorus‐containing, five‐membered P,P,P and P,N,P heterocycles were synthesized and fully characterized. The P,P,P heterocycles, 1,2,3‐triphospholanes, can be synthesized by two different facile pathways, whereas the P,N,P compound, a 1‐aza‐2,5‐diphospholane, can only be obtained with silylamine. 相似文献
Phosphorylation of suitable piperidine precursors yielded a series of novel decalin‐type O,N,P‐heterocycles. The title compounds, P(3)‐axially and P(3)‐equatorially X‐substituted, cis‐ and trans‐configurated 2,4‐dioxa‐7‐aza‐, 2,4‐dioxa‐8‐aza‐, and 2,4‐dioxa‐9‐aza‐3‐phosphabicyclo[4.4.0]decane 3‐oxides (X=Cl, F, 4‐nitrophenoxy, and 2,4‐dinitrophenoxy), are configuratively fixed and conformationally constrained P‐analogues of acetylcholine and as such represent acetylcholine (7‐aza and 9‐aza isomers) or γ‐homo‐acetylcholine mimetics (8‐aza isomers). Being irreversible inhibitors of acetylcholinesterase (AChE), the compounds are considered to be suitable probes for the investigation of the stereochemical course of the inhibition reaction by 31P‐NMR spectroscopy. Moreover, the design of these mimetics will enable studies of molecular interactions with AChE, in particular, the recognition conformation of acetylcholine. 相似文献
The spatial arrangement of the side chains of conjugated polymer backbones has critical effects on the morphology and electronic and photophysical properties of the corresponding bulk films. The effect of the side‐chain‐distribution density on the conformation at the isolated single‐polymer‐chain level was investigated with regiorandom (rra‐) poly(3‐hexylthiophene) (P3HT) and poly(3‐hexyl‐2,5‐thienylene vinylene) (P3HTV). Although pure P3HTV films are known to have low fluorescence quantum efficiencies, we observed a considerable increase in fluorescence intensity by dispersing P3HTV in poly(methyl methacrylate) (PMMA), which enabled a single‐molecule spectroscopy investigation. With single‐molecule fluorescence excitation polarization spectroscopy, we found that rra‐P3HTV single molecules form highly ordered conformations. In contrast, rra‐P3HT single molecules, display a wide variety of different conformations from isotropic to highly ordered, were observed. The experimental results are supported by extensive molecular dynamics simulations, which reveal that the reduced side‐chain‐distribution density, that is, the spaced‐out side‐chain substitution pattern, in rra‐P3HTV favors more ordered conformations compared to rra‐P3HT. Our results demonstrate that the distribution of side chains strongly affects the polymer‐chain conformation, even at the single‐molecule level, an aspect that has important implications when interpreting the macroscopic interchain packing structure exhibited by bulk polymer films. 相似文献
The cationic part of the homodifunctional aminophosphoranyl ligand, C41H41N2P2+·I?, shows interesting features associated with the N—P—C—P—N skeleton. The P—C(H) bond distances [1.696 (3) and 1.697 (3) Å] possess partial double‐bond characteristics. The nature of the P—C(H) and P—N bonds suggests that the positive charge is only distributed around the P—C—P atoms. The structure has near twofold symmetry through the central methylide‐C atom. 相似文献
The P‐coordinated boryl radical [Ph2P(naphthyl)BMes]. (Mes=mesityl) was prepared by (electro)chemical reduction of the corresponding borenium salt or bromoborane. Electron paramagnetic resonance (EPR) analysis in solution and DFT calculations indicate large spin density on boron (60–70 %) and strong P–B interactions (P→B σ donation and B→P negative hyperconjugation). The radical is persistent in solution and participates in a Gomberg‐type dimerization process. The associated quinoid‐type dimer has been characterized by single‐crystal X‐ray diffraction. 相似文献
A facile approach to bimetallic phosphides, Co‐Fe‐P, by a high‐temperature (300 °C) reaction between Co‐Fe‐O nanoparticles and trioctylphosphine is presented. The growth of Co‐Fe‐P from the Co‐Fe‐O is anisotropic. As a result, Co‐Fe‐P nanorods (from the polyhedral Co‐Fe‐O nanoparticles) and sea‐urchin‐like Co‐Fe‐P (from the cubic Co‐Fe‐O nanoparticles) are synthesized with both the nanorod and the sea‐urchin‐arm dimensions controlled by Co/Fe ratios. The Co‐Fe‐P structure, especially the sea‐urchin‐like (Co0.54Fe0.46)2P, shows enhanced catalysis for the oxygen evolution reaction in KOH with its catalytic efficiency surpassing the commercial Ir catalyst. Our synthesis is simple and may be readily extended to the preparation of other multimetallic phosphides for important catalysis and energy storage applications. 相似文献
Cytochromes P450 can catalyze various regioselective and stereospecific oxidation reactions of non‐functionalized hydrocarbons. Here, we have designed a novel light‐driven platform for cofactor‐free, whole‐cell P450 photo‐biocatalysis using eosin Y (EY) as a photosensitizer. EY can easily enter into the cytoplasm of Escherichia coli and bind specifically to the heme domain of P450. The catalytic turnover of P450 was mediated through the direct transfer of photoinduced electrons from the photosensitized EY to the P450 heme domain under visible light illumination. The photoactivation of the P450 catalytic cycle in the absence of cofactors and redox partners is successfully conducted using many bacterial P450s (variants of P450 BM3) and human P450s (CYPs 1A1, 1A2, 1B1, 2A6, 2E1, and 3A4) for the bioconversion of different substrates, including marketed drugs (simvastatin, lovastatin, and omeprazole) and a steroid (17β‐estradiol), to demonstrate the general applicability of the light‐driven, cofactor‐free system. 相似文献
The chemistry of phosphoserine [Ser(P)] containing peptides and polypeptides was extensively investigated to explore a new biomineralization material science. The selective cleavage of the O,O′‐diphenyl phospho‐protecting groups of Ser(PO3Ph2) was examined using hydrogenolysis catalysts. Among the catalysts examined, only PtO2 in 50% trifluoroacetic acid (TFA)/AcOH successfully cleaved the protecting group of Ser(PO3Ph2) to give Ser(P). Based on these characteristic new findings, Ser(P)‐containing dipeptides such as Gly‐Ser(P), Ala‐Ser(P), Ser‐Ser(P), Asp‐Ser(P), Glu‐Ser(P), and Lys‐Ser(P), and tetrapeptide [Asp‐Ser(P)]2 were synthesized by a facile method. When we used the Ser(PO3Ph2) residues at the C terminals, the amino functional groups of amino acids and peptides can be coupled by the unsymmetric mixed anhydride using isobutyl chloroformate but cannot be by the symmetric anhydride method using dicyclohexylcarbodiimide. Neither unsymmetric mixed anhydride nor symmetric anhydride can be coupled with p‐nitrophenol at their C terminals. High‐molecular‐weight sequential polypeptides containing Ser(P) such as poly[Ser(P)‐Xaa] (Xaa: Gly, Ala, Ser, Lys, Asp, Glu) and poly[Gly‐Ser(P)‐Gly] were first synthesized by the polycondensation of the di‐ and tripeptide p‐nitrophenyl active esters, followed by the quantitative elimination of the diphenyl protecting groups by PtO2 in TFA/AcOH. The new strategy to synthesize Ser(P)‐containing peptides and model proteins may help the development of hybrid formulations of marine and biomimetic protein minerals.
A carbohydrate‐derived optically active P‐chiral dioxophenylphospholane–borane complex, C27H32BO6P, was prepared from bis(diethylamino)phenylphosphine and methyl 2,6‐di‐O‐benzyl‐β‐d ‐galactopyranoside. The phosphinite was prepared with high diastereoselectivity and in good yield. The absolute configuration (R) at the P atom was deduced from the known configuration of the sugar moiety. Weak intermolecular interactions link the molecules into a three‐dimensional network. 相似文献
The title compound, C26H55N11P4, consists of a bicyclic phosphazene ring with five bulky pyrrolidino and one propylamino group, together with a second propylamino group bridging the two P atoms. The asymmetric unit contains two molecules with very similar conformations. The bulky substituents are instrumental in determining the bicyclic P4N5 ring conformation. Each of the fused six‐membered N3P3 rings is in a sofa conformation. The P—N distances in the bridge are non‐equivalent and one of them is the longest P—N bond in the molecule. The hybridization of the bridging N atom is pyramidal. The single and double P—N bonds cannot easily be distinguished, since they retain their phosphazenic character in the phosphazene macro‐rings. 相似文献