Synthesis of O-unprotected glycosyl selenoureas. A new access to bicyclic sugar isoureas

β-d-Gluco and mannopyranosyl selenoureas have been prepared by coupling of the corresponding glycosylamines with phenyl isoselenocyanate in aqueous pyridine. Alkyl and aryl isoselenocyanates, and 1,4-phenylene diisoselenocyanate have been obtained from the corresponding formamides with an excess of triphosgene, black selenium and triethylamine. Treatment of the O-unprotected β-d-glucopyranosyl selenourea with aqueous oxygen peroxide afforded a 1,2-trans-fused bicyclic isourea.     

Isoselenocyanates derived from Boc/Z-amino acids: synthesis, isolation, characterization, and application to the efficient synthesis of unsymmetrical selenoureas and selenoureidopeptidomimetics

Isoselenocyanates derived from Boc/Z-amino acids are prepared by the reaction of the corresponding isonitriles with selenium powder in presence of triethylamine at reflux. The utility of these new classes of isoselenocyanates in the preparation of selenoureidodipeptidomimetics possessing both amino as well as carboxy termini has been accomplished. The ¹H NMR analysis confirmed that the protocol involving the conversion of isonitriles to isoselenocyanates and their use as coupling agents in assembling selenoureido derivatives is free from racemization.     

Synthesis of 2-amino-1,3,4-oxadiazoles from isoselenocyanates via cyclodeselenization

An efficient one-pot method to access 2-amino-1,3,4-oxadiazoles from isoselenocyanates and hydrazides or dihydrazides was developed via cyclodeselenization. Without any harsh reagents, various 2-amino-1,3,4-oxadiazoles were obtained in considerably high yields (82%-97%) and purities (>99%) directly with simple crystallization in ethanol. And the formed precipitated Se powder during the reaction could be recycled for preparation of isoselenocyanates efficiently. A plausible mechanism is proposed for the formation of the target products.     

Selenium-containing heterocycles from isoselenocyanates: synthesis of 2-methylidene-1,3-selenazolidine derivatives

A convenient and unequivocal synthesis of the title compounds from isoselenocyanates, malononitrile or 2-cyanoacetate, and 1,2-dibromoethane or α-halogenated carboxylic acid derivatives is reported. The proposed reaction mechanism involves in situ cyclization of different halogenated compounds with an intermediate keten-N,Se-acetal, generated by the base promoted nucleophilic addition of the acidic cyanomethylenes to aliphatic and aromatic isoselenocyanates. Chemical and spectroscopic evidence for the structures of the new compounds is presented.     

Selective synthesis of novel 2-imino-1,3-selenazolidin-4-ones and 2-amino-1,3,4-selenadiazin-5-ones from isoselenocyanates

An efficient and regioselective synthesis of 2-imino-1,3-selenazolidin-4-ones and 2-amino-1,3,4-selenadiazin-5-ones was achieved via one-pot reaction of isoselenocyanates, hydrazines, and ethyl chloroacetate or chloroacetyl chloride, respectively. Plausible mechanisms for these transformations were given.     

Sodium fluoride as an effcient catalyst for the synthesis of 2,4- disubstituted-1,3-thiazoles and selenazoles at ambient temperature简

Sodium fluoride was found to be a simple, mild and efficient catalyst for the synthesis of 2,4-disubstituted 1,3-thiazoles and selenazoles utilizing phenacyl bromides/3-(2-bromoacetyl)-2H-chromen-2-one and thiourea/phenylthiourea/selenourea in aqueous methanol at ambient temperature. Analytically pure products are formed within 1–3 min in excellent yields.     

Novel heterocyclic selenazadiphospholaminediselenides, zwitterionic carbamidoyl(phenyl)-phosphinodiselenoic acids and selenoureas derived from cyanamides

2,4-Bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (Woollins’ reagent, WR) reacts with cyanamides (1a-h) in refluxing toluene to afford a series of novel selenazadiphospholaminediselenides (RR′NCN(PhP(Se)SeP(Se)Ph, R=C₆H₅(CH₂)_1-3, 4-n-C₁₀H₂₁C₆H₄ and 4-BrC₆H₄CH₂; R′=H, CH₃, C₂H₅ and C(O)OC₂H₅2a-g). Post-treatment of the reaction mixture with water led to the formation of carbamidoyl(phenyl)phosphinodiselenoic acids (RR′NC(NH₂)P(SeH)₂Ph, R=C₆H₅(CH₂)_2-3, 4-n-C₁₀H₂₁C₆H₄ and 4-BrC₆H₄CH₂; R′=H and CH₃, 3b, 3c, 3e and 3f) and selenoureas (RR′NC(Se)NH₂, R=C₆H₅(CH)_1-2; R′=CH₃ and OC(O)C₂H₅, 4f and 4h) in moderate to excellent yields. All new compounds are characterised spectroscopically and five X-ray crystal structures are reported.     

Synthesis of 5-amino-2-selenoxo-1,3-imidazole-4-carboselenoamides by the reaction of isoselenocyanates with aminoacetonitriles

Reaction of isoselenocyanates with aminoacetonitriles afforded 4-amino-2-selenoxo-1,3-imidazole-2-selenones, whereas reaction with aminopropionitriles led to selenoureas. We confirmed that it is easy to distinguish between selenoamides and selenoureas by comparison of their chemical shift differences in the ⁷⁷Se NMR spectra.     

Synthesis of non-glycosidically linked selenoether pseudodisaccharides

Non-glycosidically linked disaccharide mimetics with a selenoether functionality linking the two monosaccharide residues have been synthesised. Protected Glc(Se3-3)Glc, Glc(Se3-6)Glc and Glc(Se3-6)Man structures were obtained. Selenium was introduced by displacement of carbohydrate sulfonates with a selenobenzoate anion. Conversion into diselenides by methanolysis of the benzoate and aerial oxidation was followed by reduction of the diselenides to selenolates, and in situ displacement of a second carbohydrate sulfonate in an S_N2 reaction to give selenoethers. Glc(Se3-3)Glc and Glc(Se3-6)Glc were also obtained in deprotected form.     

Selenium‐Containing Heterocycles from Isoselenocyanates: 4‐Methylselenazole Derivatives from the Reaction with Malononitrile and Propargyl Chloride

Aryl isoselenocyanates 1 react with malononitrile ( 6a ) and propargyl chloride ( 8 ) in DMF in the presence of Et₃N to give the corresponding 2‐(3‐aryl‐2,3‐dihydro‐4‐methyl‐1,3‐selenazol‐2‐ylidene)malononitriles 12 as major products. The analogous reaction takes place with benzoylacetonitrile ( 6f ) instead of 6a . In some cases, the corresponding noncyclic 2‐[(arylamino)(prop‐2‐ynylselanyl)methylidene]malononitriles 9 were obtained as minor products. The structures of 9e and 11a have been established by X‐ray crystallography.     

Synthesis and biological applications of selenoureas

In this review article we have discussed synthesis, free radical scavenging, enzyme inhibition, anticancer activity, DNA binding of selenoureas and detection of selenium species. We have given the structure and activity relationships of different selenoureas with each other and with their sulfur homologues (thioureas). Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and Spectroscopic Characterization of Arylated Selenoureas

Abstract

Selenoureas were prepared from isoselenocyanates and structurally characterized by spectroscopic methods and by X-ray crystal structure analyses.     

Synthesis of N-benzoyl-N''-aryl selenoureas under PTC

Recently many syntheses of selenium-containing compounds have been reported and studied, in which compounds selenoureas are used as the precursors for the syntheses of selenium-nitrogen heterocyclic compounds and their activities have received increasing attentions.Herein, we report the facile preparation of N-benzoyl-N'-aryl selenourea derivatives using potassium selenocyanate.In this typical procedure, Benzoyl chloride 1 was treated with potassium selenocyanate in CH2C12 under the condition of solid-liquid phase transfer catalysis using polyethylene glycal-400 as the catalyst to give the corresponding benzoyl isoselenocyanate 2. This compound did not need to be isolated and reacted with aromatic amine affording the N-benzoyl-N'-aryl selenourea derivatives 3.The reaction is described as:All the experiments were carried out under the condition of solid-liquid phase transfer catalysis using polyethylene glycal-400 as the catalyst and room temperature. And the structure was determined by IR, 1H NMR and 13C NMR. Selected data for N-benzoyl-N'-(4-fluoro)-selenourea:IR(KBr) 3426, 3274, 1672,1234,1155(C=Se); 1HMR(500MHz, DMSO) δ 12.85 (1H,S),11.86(1H,S), 7.27(2H,d,J=2.15), 7.98(2H,s,J=l.15), 7.30(2H,d,J=2.05), 7.56(2H.t,J=6.50),7.67(1H,t,J=6.20); 13C NMR(500MHz, DMSO)δ 181,168(C=Se),135,133, 132,115, 128.3, 128.8,161, 129.     

The Synthesis of Rare Sugars

The use of new oxidation reagents, such as the Pfitzner-Moffatt reagent, dimethyl sulfoxide-acid anhydrides, and ruthenium tetroxide, has significantly improved the yields obtained on oxidation of a secondary hydroxyl group to a carbonyl group in suitably protected sugars. The application of these new oxidants in the carbohydrate field is briefly surveyed. The product ketones are convenient intermediates for syntheses of amino, branched-chain, deoxy, and other rare sugars. Some representative syntheses are illustrated.     

Synthesis of sugar-derived spiroaminals via lactamization and metathesis reactions

A series of sugar-derived spiroaminals has been synthesized by utilizing cross metathesis, ring closing metathesis and lactamization reactions as key steps from 1-C-alkylated glycosyl azides and important correlations in the spectral data between spiroaminals and their respective anomers are reported.     

Reactions of nitroxides,part 7: Synthesis of novel nitroxide selenoureas

The reactions of 4‐isoselenocyanato‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl with selected amines and lower alcohols give the corresponding novel selenoureas and selenocarbamates, all bearing the nitroxyl moiety. Some of the synthesized selenoureas and selenocarbamates show moderate‐to‐good activity against pathogenic fungi. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:549–556, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20454     

Novel dibenzosuberene substituted aroyl selenoureas: Synthesis,crystal structure,DFT, molecular docking and biological studies

Abstract

A series of aroyl selenourea dibenzosuberene (1–3) derivatives were synthesized and characterized by different analytical methods and single crystal X-ray crystallography. Quantum chemical computations were made using DFT to determine the structural and molecular properties of the compounds. The in vitro antibacterial action of the compounds was evaluated against chosen gram-negative (Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli), and gram-positive (Bacillus subtilis, Staphylococcus aureus, and Staphylococcus epidermidis) bacteria for their antifungal activity against Curvularia lunata, Penicillium notatum, and Aspergillus niger. Using molecular docking studies, the binding modes were understood along with the mechanism in opposing the target protein MurB.     

Synthesis of 1,3‐Selenazol‐2(3H)‐imines

The reaction of N,N′‐diarylselenoureas 16 with phenacyl bromide in EtOH under reflux, followed by treatment with NH₃, gave N,3‐diaryl‐4‐phenyl‐1,3‐selenazol‐2(3H)‐imines 13 in high yields (Scheme 2). A reaction mechanism via formation of the corresponding Se‐(benzoylmethyl)isoselenoureas 18 and subsequent cyclocondensation is proposed (Scheme 3). The N,N′‐diarylselenoureas 16 were conveniently prepared by the reaction of aryl isoselenocyanates 15 with 4‐substituted anilines. The structures of 13a and 13c were established by X‐ray crystallography.     

Synthesis of sugar-derived phostones by activation of γ-hydroxyphosphonic acids

Treatment of carbohydrate-derived γ-hydroxyphosphonic acids under usual acetylation conditions affords the corresponding phostones in good yield. The method could be used for the preparation of free phostones as well as α- and β-phosphonomethylarabinose.     

Synthesis of Hyperbranched Aminopolysaccharides

Sugar dihydroozaxole monomers with two free hydroxyl groups undergo acid-catalyzed polymerization to hyperbranched aminopolysaccharides [Eq. (a)]. Their molecular weights were determined by the light-scattering method to be between 2.3×10⁵ and 7.6×10⁵. The degree of branching determined by ¹H NMR spectroscopy after reaction with [iPr₂Si(Cl)]₂O is close to the ideal value. Ts=MeC₆H₄SO₂, CSA=10-camphorsulfonic acid.