Phosphonium Bromides (phosphonium + bromide)

Distribution by Scientific Domains


Selected Abstracts


A simple and highly successful C-terminal sequence analysis of proteins by mass spectrometry

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2008
Hiroki Kuyama Dr.
Abstract A simple and efficient method for C-terminal sequencing of proteins has long been pursued because it would provide substantial information for identifying the covalent structure, including post-translational modifications. However, there are still significant impediments to both direct sequencing from C termini of proteins and specific isolation of C-terminal peptides from proteins. We describe here a highly successful, de novo C-terminal sequencing method of proteins by employing succinimidyloxycarbonylmethyl tris (2,4,6-trimethoxyphenyl) phosphonium bromide and mass spectrometry. [source]


New Monodentate P,C-Stereogenic Bicyclic Phosphanes: 1-Phenyl-1,3a,4,5,6,6a-hexahydrocyclopenta[b]phosphole and 1-Phenyloctahydrocyclopenta[b]phosphole

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2004
Zbigniew Pakulski
Abstract Racemic1-phenyl-1,3a,4,5,6,6a-hexahydrocyclopenta[b]phosphole (4) was separated into enantiomerically pure 1-phenyl-1,3a,4,5,6,6a-hexahydrocyclopenta[b]phosphole 1-oxides [(RP)- 6 and (SP)- 6] by an oxidative resolution procedure involving treatment of 4 with menthyl bromoacetate, crystallization of the resulting diastereoisomeric phosphonium bromides 8, and stereoselective hydrolysis of the diastereomerically pure salts to the corresponding enantiomerically pure phosphane oxides. Stereoretentive reduction of P=O in (RP)- 6 gave enantiomerically pure (SP)- 4. Hydrogenation of (SP)- 6 and subsequent reduction of P=O afforded saturated 1-phenyloctahydrocyclopenta[b]phosphole [(RP)- 5]. Monophosphanes (SP)- 4 and (RP)- 5 were tested as chiral ligands and catalysts in model asymmetric hydrogenation and C,C bond-forming reactions. Enantioselectivities of up to 95% were observed. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


Effect of intercalating agents on clay dispersion and thermal properties in polyethylene/montmorillonite nanocomposites

POLYMER ENGINEERING & SCIENCE, Issue 8 2008
Karen Stoeffler
Alkyl pyridinium, 1-vinyl alkyl imidazolium, 1,3-dialkyl imidazolium, and tetraalkyl phosphonium bromides were successfully used as intercalants for the preparation of highly thermally stable organophilic montmorillonites. Nanocomposites of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted with maleic anhydride (LLDPE/LLDPE- g -MAH) were prepared from those organoclays. The micro- and nano-dispersions were analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM): intercalation and/or partial exfoliation were found to occur only for formulations based on organoclays having an initial basal distance higher than 20 , suggesting the existence of a critical interfoliar distance for the delamination of silicate layers in a noninteracting polymer matrix. The properties of the nanocomposites were analyzed through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and oscillatory rheometry. The dynamic crystallization of LLDPE was not significantly affected by the presence of clay. TGA in oxidative atmosphere proved to be very sensitive to the dispersion state of the organoclay: the thermal stability was drastically enhanced for intercalated and partially exfoliated formulations. However, the inherent thermal stability of the organoclay did not appear to influence significantly the overall thermal stability of the composite in the range of temperatures investigated (160,230C). POLYM. ENG. SCI., 2008. 2008 Society of Plastics Engineers. [source]


Stereoselective synthesis of (Z)-5-(Trideca-4-enyl)resorcinol and gibbilimbols A,D

CHINESE JOURNAL OF CHEMISTRY, Issue 11 2004
Ling Zhou
Abstract (Z)-5,(Trideca-4-enyl)resorcinol (1) and gibbilimbols A,D (2,5) were synthesized in 47%-60% yields over 6 steps from commercially available starting materials. The Wittig reaction of various alkyl phosphonium bromides with appropriate aldehydes in the presence of potassium ten-butoxide (t -BuOK) in anhydrous THF solution at room temperature served as the key step, and the result showed that only (Z)-configuration olefins were formed by this procedure. The synthesis of the (Z)-5-(trideca-4-enyl)resorcinol (1) was reported for the first time. [source]