Pentafluorophenyl sulfonate ester as a protecting group for the preparation of biaryl- and heterobiaryl sulfonate esters

The use of the pentafluorophenyl (PFP) group as a sulfonic acid protecting group has allowed the synthesis of new biaryl- and heterobiaryl-PFP-sulfonate esters by use of the Suzuki-Miyaura reaction. The successful employment of a novel inorganic base, anhydrous sodium tetraborate, was crucial to give the products in excellent yields. The PFP-sulfonate ester has been previously shown to be an excellent alternative to sulfonyl chlorides in the synthesis of sulfonamides. [structure: see text]     

Induction and inhibition of novel sulfotransferase in a human intestinal bacterium, Eubacterium sp. A-44

Induction and inhibition of a novel sulfotransferase produced by Eubacterium sp. A-44 isolated from human feces have been studied. Production of the enzyme was induced by phenylsulfate esters, sulfate donor substrates, but not by phenols, sulfate acceptor substrates, or inorganic sulfate. p-Nitrophenylsulfate (PNS), a good donor substrate, stimulated enzyme production more than 10-fold. Sulfotransferase production was strongly inhibited by phenylphosphate esters. Enzyme activity was competitively inhibited by phenylphosphate esters, but not by inorganic phosphate. High yields of sulfotransferase from sonicated cells were obtained when the bacteria were grown in a media containing 0.6% (w/v) or less of glycine.     

Brønsted acid catalyzed formal insertion of isocyanides into a C-O bond of acetals

The Br?nsted acid catalyzed formal insertion of an isocyanide into a C-O bond of an acetal is described. A diverse array of acyclic and cyclic acetals can be applied to the catalytic insertion to form alpha-alkoxy imidates. Functional groups, such as nitro, cyano, halogen, ester, and alkoxy groups, are tolerant to the reaction conditions employed. The course of the reaction is highly dependent on the structure of the isocyanide. The use of an electron-deficient aryl isocyanide, such as 2c and 2d, is required to selectively obtain the monoinsertion product. When aryl isocyanides containing alkyl substituents, such as 2a and 2b, are employed, two molecules of the isocyanide are incorporated, and the double-insertion product is obtained. The reaction of tert-octyl isocyanide also induces a double incorporation, but the subsequent acid-mediated fragmentation leads to the 2-alkoxy imidoyl cyanide. The monoinsertion products, alpha-alkoxy imidates, can readily be hydrolyzed to alpha-alkoxy esters, realizing the formal carbonylation of an acetal.     

Synthesis and Anticoagulant Activity of Bioisosteric Sulfonic‐Acid Analogues of the Antithrombin‐Binding Pentasaccharide Domain of Heparin

Two pentasaccharide sulfonic acids that were related to the antithrombin‐binding domain of heparin were prepared, in which two or three primary sulfate esters were replaced by sodium‐sulfonatomethyl moieties. The sulfonic‐acid groups were formed on a monosaccharide level and the obtained carbohydrate sulfonic‐acid esters were found to be excellent donors and acceptors in the glycosylation reactions. Throughout the synthesis, the hydroxy groups to be methylated were masked in the form of acetates and the hydroxy groups to be sulfated were masked with benzyl groups. The disulfonic‐acid analogue was prepared in a [2+3] block synthesis by using a trisaccharide disulfonic acid as an acceptor and a glucuronide disaccharide as a donor. For the synthesis of the pentasaccharide trisulfonic acid, a more‐efficient approach, which involved elongation of the trisaccharide acceptor with a non‐oxidized precursor of the glucuronic acid followed by post‐glycosidation oxidation at the tetrasaccharide level and a subsequent [1+4] coupling reaction, was elaborated. In vitro evaluation of the anticoagulant activity of these new sulfonic‐acid derivatives revealed that the disulfonate analogue inhibited the blood‐coagulation‐proteinase factor Xa with outstanding efficacy; however, the introduction of the third sulfonic‐acid moiety resulted in a notable decrease in the anti‐Xa activity. The difference in the biological activity of the disulfonic‐ and trisulfonic‐acid counterparts could be explained by the different conformation of their L ‐iduronic‐acid residues.     

Reaction of carboxamide with Cu2Oisonitrile complex; formation of a new chelated copper(I) complex

Reaction of carboxamides with Cu₂O in the presence of t-butyl isocyanide gave new chelated copper(I) complexes, which probably are formed by the insertion of t-butyl isocyanide into the coppernitrogen bond of copper(I) amide isonitrile complexes, which were initially produced from the carboxamides and Cu₂Ot-butyl isocyanide complex. The same chelated copper(I) complexes were prepared more readily by the reaction of the corresponding N-trimethylsilyl-carboxamides with Cu₂Ot-butyl isocyanide complex. Reactions of the copper(I) complexes thus obtained with alkylating agents, such as alkyl halides, alkyl tosylates and triethyloxonium tetrafluoroborate, also were described.     

An Efficient Method for Sulfonylation of Amines,Alcohols and Phenols with N-Fluorobenzenesulfonimide Under Mild Conditions

A new and convenient procedure was developed for the preparation of sulfonamides and sulfonic esters using N-fluorobenzenesulfonimide(NFSI) as a novel phenylsulfonyl group transfer reagent. In this protocol, a broad range of functional groups were tolerated to give the corresponding sulfonamides or sulfonic esters in moderate to excellent yields. The synthetic strategy for sulfonamides formation proceeded efficiently even under base-, metal-and additive-free conditions with the advantages of operational simplicity, mild reaction conditions as well as short reaction time.     

Synthesis of Diversely Functionalized Oxindoles Enabled by Migratory Insertion of Isocyanide to a Transient σ‐Alkylpalladium(II) Complex

Palladium‐catalyzed intramolecular carbopalladation of N‐aryl acrylamides followed by migratory insertion of an isocyanide‐coordinated C(sp³)?Pd intermediate afforded an alkylimidoyl?Pd^II complex, which can be intercepted by a nucleophile, including heteroarenes. In addition to amides, the alkylimidoyl?Pd^II complex was successfully converted into esters, ketones, and bis‐heterocyclic compounds. An unprecedented palladium‐catalyzed enantioselective domino process involving isocyanide was also documented.     

Diastereoselective synthesis of 5-iminooxazolines and their subsequent transformation to α,α-disubstituted dipeptide esters: a formal [4+1] cycloaddition reaction of cyclohexyl isocyanide and Z-alkyl-α-benzoyl amino-acrylates

A novel atom economical diastereoselective synthesis of 5-iminooxazolines and their subsequent transformation to α,α-disubstituted dipeptide esters is described. Heating a mixture of cyclohexyl isocyanide and Z-α-benzoyl amino-acrylic acid alkyl esters under solvent-free conditions, afforded 5-iminooxazolines, which, upon specifications provided α,α-disubstituted dipeptide esters in good yield.     

Copper‐mediated simple and direct aerobic oxidative esterification of arylacetonitriles with alcohols/phenols

A simple and direct aerobic oxidative esterification reaction of arylacetonitriles with alcohols/phenols is achieved in the presence of a copper salt and molecular oxygen, which produces a broad range of aryl carboxylic acid esters in good to high yields. Copper salt plays multiple roles in the transformation, which allows the oxygenation of C? H bond, cleavage of inert C? C bond, and formation of C? O bond in one pot without the assistance of any of the acids, bases, ligands, and so on. The reaction provides a simple, direct, and efficient protocol towards functionalized esters, especially aryl benzoates, from readily available starting materials.     

Pyrazinium Di(hydrogen sulfate) as a Novel,Highly Efficient and Homogeneous Catalyst for the Condensation of Enolizable Ketones with Aldehydes,Acetonitrile and Acetyl Chloride

A highly efficient protocol for the synthesis of β‐acetamido ketone or ester derivatives in the presence of pyrazinium di(hydrogen sulfate) {Py(OSO₃H)₂} as a novel, green and homogeneous solid acid catalyst at room temperature is described. One‐pot multi‐component condensation of enolizable ketones or alkyl acetoacetates with aldehydes, acetonitrile and acetyl chloride affords the title compounds in high to excellent yields and in relatively short reaction times. In this work, the efficiency of our recently reported solid acid catalyst, saccharin sulfonic acid (Sa‐SO₃H), in the synthesis of β‐acetamido ketones/esters is also studied. Moreover, in this research, some new β‐acetamido ketones and esters (i.e. one complex structure) are prepared.     

Two-step synthesis of ferrocenyl esters of vanillic acid

Successive reactions of vanillin with aromatic aldehydes at the phenol group and ferroceneboronic acid at the carbonyl group catalyzed with various N-heterocyclic carbenes afforded the corresponding ferrocenyl esters. In these reactions copper(II) sulfate, cinnamic aldehyde, and air oxygen act as oxidants. The resulting ferrocenyl esters of vanillic acid were tested for cytotoxicity.     

Biosynthetic pathways to dichloroimines; precursor incorporation studies on terpene metabolites in the tropical marine sponge Stylotella aurantium

The biosynthetic origin of the dichloroimine functional group in the marine sponge terpene metabolites stylotellanes A (3) and B (4) was probed by the use of [(14)C]-labelled precursor experiments. Incubation of the sponge Stylotella aurantium with [(14)C]-labelled cyanide or thiocyanate resulted in radioactive terpenes in which the radiolabel was shown by hydrolytic chemical degradation to be associated specifically with the dichloroimine carbons. Additionally, label from both precursors was incorporated into farnesyl isothiocyanate (2). A time course experiment with [(14)C]-cyanide revealed that the specific activity for farnesyl isothiocyanate decreases over time, but increases for stylotellane B (4), consistent with the rapid formation of farnesyl isothiocyanate (2) from inorganic precursors followed by a slower conversion to stylotellane B (4). The advanced precursors farnesyl isothiocyanate (2) and farnesyl isocyanide (5) were supplied to S. aurantium, and shown to be incorporated efficiently into stylotellane A (3) and B (4). Feeding of [(14)C]-farnesyl isothiocyanate (2) resulted in a higher incorporation of label than with [(14)C]-farnesyl isocyanide (5). Farnesyl isocyanide was incorporated into farnesyl isothiocyanate in agreement with labelling studies in other marine sponges. Both farnesyl isocyanide and isothiocyanate were further incorporated into axinyssamide A (11) as well as the cyclized dichloroimines (12)-(14), (16) that represent more advanced biosynthetic products of this pathway. These results identify the likely biosynthetic pathway leading to the major metabolites of S. aurantium.     

Indirect atomic absorption spectrometric determination of sulfate in human blood serum.

An indirect method for the determination of sulfate by atomic absorption spectrometry (AAS) is described. Sulfate forms a stable ion-association complex, [Cu(neocuproine)2]2+(SO4(2-)), in neutral medium, which can be extracted into isobutyl methyl ketone in the presence of a polar medium (methanol) with an efficiency higher than 98.0% and the extract can be analysed directly for copper (and hence indirectly for sulfate) by AAS. Measurement of the copper atomic absorption signal from the organic phase allows the indirect determination of 0.14-1.12 micrograms ml-1 of sulfate, giving a 450-fold increase in sensitivity over the conventional method of precipitation with barium. The limit of detection (3 sigma) is 3.2 ng ml-1 which is better than that of ion chromatography (0.15 micrograms ml-1). Indirect AAS allows the accurate assay of inorganic sulfate anion in biological fluids and tissues. The sulfate concentration determined by the proposed method in human blood serum (n = 6 in each instance) was 35.4-43.3 micrograms ml-1 in normal persons, 50.3-62.5 micrograms ml-1 in jaundice patients and 83.3-155.6 micrograms ml-1 in diabetic patients. A good correlation between measured sulfate and the sulfate added to blood serum was obtained.     

A simple and efficient method for sulfonylation of amines, alcohols and phenols with cupric oxide under mild conditions

Cupric Oxide efficiently catalyzed the synthesis of sulfonamides and sulfonic esters. This method has been applied to a variety of substrates including nucleophilic and sterically-hindered amines, alcohols and phenols with excellent yields of sulfonamides and sulfonic esters. The remarkable selectivity under mild and neutral conditions of this commercially available inexpensive catalyst is an attractive feature of this method.     

Use of Some Silver Salts of Aromatic Sulfonic Acids in Thin-Layer Chromatography

Abstract

Some silver salts of aromatic sulfonic acids were used for thin-layer impregnation. The chromatographic properties of these salts were examined by separation of fatty acid methyl esters with different degrees of saturation as well as of their cis- and trans-isomers. Benzene sulfonic acid silver salt was more thoroughly investigated. An attempt was made to prove the effect of the anion of the different silver salts on the R_f values of a model mixture of fatty acid methyl esters.     

Synthesis of isocyanide derivatives of α-aminoalkylphosphonate diphenyl esters

This letter describes the first example of the synthesis of isocyanide derivatives of α-aminoalkylphosphonate diphenyl esters. This method produces the title compounds in high purity and in very good yields. It also permits the generation of an α-aminophosphonate-based library of biologically active phosphonopeptides. Preliminary experiments demonstrate their application as substrates for the Ugi-type multicomponent condensation.     

Sulfur dioxide Plasma Treatment of the Clay (Laponite) Particles

Low temperature plasma treatment of the inorganic clay (Laponite) using sulfur dioxide (SO₂) as a process gas was carried out in order to graft the functional groups containing sulfur and oxygen (sulfonic acid groups) onto the inert clay surface. Conditions for SO₂ plasma modification were optimized by the measurement of the sulfur content as a function of the plasma power, gas flow rate and treatment time. It was found that the sulfur content increased with the increasing of the plasma power as well as the treatment time. Optical emission spectroscopy was presented in order to control the plasma phase and to characterize the different excitation processes of atomic species in SO₂ plasma under different discharge conditions. X-ray diffraction spectrometry, X-ray photoelectron spectroscopy, FTIR and thermal analysis measurements of grafted Laponite powder completed the characterization.     

异腈氮杂配铜配合物的合成及光解水制氢性能

设计、合成了供电子性能的异腈二齿配体,可与铜(Ⅰ)和1,10-菲咯啉衍生物发生反应,形成一类异腈氮杂配铜光敏剂4a~4h,并在光解水制氢体系研究了其光催化活性。实验结果表明,2,2′-二异腈基二苯硫醚与2,9位具有取代基的菲咯啉形成的杂配铜配合物具有一定的光敏活性,光解水制氢TON达168。结合这类配合物的光物理性能和光电性能研究,对这类配合物作为光敏剂的构效关系及其内在机理进行了初步地解释与探讨。     

Three-Component,One-Pot Synthesis of New Functionalized Pyrrolines

The addition of acetylenic esters to diethyl acetamidomalonate in the presence of tert-butyl isocyanide leads to highly functionalized 1-pyrrolines and 2-pyrroline.     

异腈氮杂配铜配合物的合成及光解水制氢性能

设计、合成了供电子性能的异腈二齿配体,可与铜（Ⅰ）和1,10-菲咯啉衍生物发生反应,形成一类异腈氮杂配铜光敏剂4a~4h,并在光解水制氢体系研究了其光催化活性。实验结果表明,2,2''-二异腈基二苯硫醚与2,9位具有取代基的菲咯啉形成的杂配铜配合物具有一定的光敏活性,光解水制氢TON达168。结合这类配合物的光物理性能和光电性能研究,对这类配合物作为光敏剂的构效关系及其内在机理进行了初步地解释与探讨。