Elaiomycins B and C: alkylhydrazide antibiotics from Streptomyces sp. BK 190

Two novel alkyhydrazides, elaiomycins B and C, together with the azoxy antibiotic elaiomycin were isolated from Streptomyces sp. BK 190. The structures were established by 1D- and 2D-NMR spectroscopy including (15)N NMR studies and high-resolution orbitrap-ESI-mass spectrometry.     

MECANISME D'ELIMINATION AVEC FORMATION DE VINYLPHOSPHONIUMS DANS L'HYDROLYSE BASIQUE DES SELS DE PHOSPHONIUMS

Abstract

In basic hydrolysis of the phosphonium salts (4), (C₆H₅)₃P–CH₂CH₂Y X^?, vinylphosphonium salts (5), (C₆H₅)₃P–CH?CH₂ X^?, are formed by an elimination mechanism. This mechanism takes place for the leaving groups Y = OC₆H₅. OAc, OH and Br, but not for the groups Y = OEt, SC₆H₅, SEt. The elimination reaction appears to be favoured of two reasons: primarily the leaving group ability of the Y group but also the possibility of intramolecular interaction between the Y group and the phosphorus atom. The hydroxide ion, the acetate ion and the phenolate ion seen to react by this elimination mechanism, but not the thiolate ions.

Dans l'hydrolyse basique des sels de phosphoniums (4), (C₆H₅)₃P–CH₂CH₂Y X^?, le mecanisme d'élimination correspondant à la formation du vinylphosphonium (5) est mis en évidence par la réaction (4). Ce mécanisme intervient pour les groupes partants Y = OC₆H₅, OAc, OH et Br, mais il n'intervient pas pour les groupes Y = OEt, SC₆H₅, SEt. L'aptitude des groupes Y à étre éliminés des sels (4) parait résulter de la superposition de deux facteurs: d'une part, la facilité de départ intrinseque du groupe Y, et, d'autre part, la possibilité d'interactions intramoleculaires entre le groupe Y et l'atome de phosphore. Le mécanisme d'élimination peut étre initié par les ions hydroxyde, acétate ou phénolate, mais il ne l'est pas par les ions thiolates.     

An efficient,one‐pot and CuCl‐catalyzed route to the synthesis of symmetric organic disulfides via domino reactions of thioacetamide and aryl (alkyl) halides

In this article, a simple, general and novel method for the synthesis of diaryl (dialkyl) disulfides from aryl (alkyl) halides is described. This is a convenient approach that involves the use of commercially available and inexpensive thioacetamide as a sulfur transfer reagent in the domino process for the synthesis of symmetric organic disulfides. Copyright © 2013 John Wiley & Sons, Ltd.     

Influence of High-pressure Treatment on Gelation of Skim Milk Powder+Low Methoxyl Pectin Dispersions

High-pressure treatment (HPT) of skim milk powder (SMP) dispersions in the absence of added sugar has been found to cause substantial changes in the storage and loss moduli. In particular, HPT ( S 500 MPa) led to stable gel formation at lower protein contents in the presence of added sucrose, fructose and glucose. At each milk protein concentration, the position of the phase boundary in the sol-gel phase diagram defines the critical sugar concentration required for pressure-induced gelation. Surprisingly, once the total sugar content exceeds 40-45 wt%, the gelation becomes inhibited again. HPT of low methoxyl pectin (LMP) solutions (>0.1 wt%) showed significant increase in the viscoelastic properties. These changes, both in the absence and presence of sucrose, were higher than for the untreated samples. Pressurisation of the SMP dispersions containing constant quantities of LMP and total soluble solids (TSS) led to considerable increases in their rheological properties compared with untreated ones.     

Lower Bounds for the Principal Eigenvalue of the p-Laplacian on the Unit Ball

Abstract

In this paper, by the sub-super solution method we provide explicit lower bounds for the principal eigenvalue of the p-Laplacian on the unit ball. We compare our results with those of earlier studies and also demonstrate that they are in good agreement with numerical results.     

Homomorphic solution of fully fuzzy linear systems

In this paper, a fully fuzzy linear system (FFLS) is considered. By defuzzifying, the (n × n) FFLS can be replaced by three (n × n) crisp linear systems, and consequently its homomorphic solution in canonical trapezoidal form based on three (n × n) crisp linear solutions associated with three parameters, value, ambiguity, and fuzziness, is calculated.     

Characterization of aerosols generated from nine nanomaterial powders: reliability with regard to in vivo inhalation toxicology studies

Journal of Nanoparticle Research - A simple one-pot hydrothermal approach has been provided for the synthesis of a magnetically recyclable Co3O4/Co(OH)2/RGO ternary visible-light photocatalyst. The...     

Synthesis of New Fused Hetecrocyclic Compounds of Benzpyrid‐4‐One Derivatives and Their Some Biological Activity

A series of fused pyrazolino‐, Isoxazolino‐, Pyrimidino‐, Pyrimidinothino‐, thiazolidinones and β‐lactam incorporating benzpyrid‐4‐one derivatives have been synthesized by different methods of chemical reaction. The prepared compounds were established by universals and modern methods of physical and chemical confirmation.     

Synthesis of 1,3-diarylacetones from N-(arylacetyl)benzotriazoles via arylketene intermediates

Several 1-acylbenzotriazoles were synthesized and treated with sodium hydride to afford symmetrical ketones via the dimerization of intermediate ketenes followed by hydrolysis and the loss of carbon dioxide. © 1996 John Wiley & Sons, Inc.     

Synthesis of Some New 3-Oxo-2-[(Z)-1-phenylmethylidene]-5H-[1,3]thiazolo[3,2-a]-and N-Acetylated Pyrimidines

3-Oxo-2-[(Z)-1-phenylmethylidene]-5H-[1,3]thiazolo[3,2-a] pyrimidine derivatives 2a–f were synthesized by the reaction of an appropriate 3,4-dihydro-2(H)-pyrimidone 1 , chloroacetic acid, sodium acetate and benzaldehyde. Reaction of 1 with acetic anhydride under heating afforded only 3-N-acetylated 3,4-dihydro-2(H)-pyrimidines 3a–f . The yields of the products after recrystallization from ethanol were of the order of 60–92 %. IR, ¹ H NMR spectroscopy, and elemental analysis were used for the identification of these compounds.