Synthesis of stable oxazolidine nitroxyl radicals with methoxy groups at the α-carbon atoms to the radical site

The condensation of -hydroxyaminoalcohols with aldehydes and acetone gave 3-hydroxyoxazolidines and tautomeric N-(2-hydroxyethyl)--arylnitrones, whose oxidation by PbO₂ in methanol leads to stable oxazolidine nitroxyl radicals with methoxy groups at C² and C⁴.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 966–973, April, 1992.     

A calorimetric and carbon-13 NMR spectral analysis of the protonation in asymmetric α,ω-thiadiamines

Enthalpies of protonation and ¹³C-NMR chemical shifts are used to calculate the fractional protonation at each basic site in α,ω-thiadiamines. Results are discussed in terms of the inductive effects exercised by the central thioether group on both terminal aminofunctions.     

Encapsulation of alkylparabens with natural and modified α- and β-cyclodextrins

The inclusion complexation between methylparaben, ethylparaben, propylparaben, butylparaben with α-CD, β-CD, hydroxypropyl α-cyclodextrin and hydroxypropyl β-cyclodextrin were carried out by UV–Vis, steady state and time-resolved fluorescence, FT-IR, ¹H NMR techniques and semi-empirical method (PM3). The drug molecules are all given one emission maximum in water where as dual emission in all the CDs. CDs study revealed that the paraben molecules were formed 1:1 inclusion complex. The aliphatic side chain is present in the hydrophilic part whereas hydroxyl group is present in the hydrophobic part of the CD cavity. Nanosecond time-resolved studies indicated that paraben exhibited biexponential decay in water whereas triexponential decay in CDs solution. The complexation energy, thermodynamic parameters and HOMO–LUMO energy structure were calculated using quantum chemical calculation.     

Synthesis with organoboranes. 21. Synthesis of α- and gd-bamascone

Selective syntheses of α- and gd-damascone, using allylic organoboranes as the key intermediates, are described.     

The Application of the Trichloroacetimidate Method to the Synthesis of α-D-Gluco- and α-D-Galactopyranosides

Abstract

The trichloroacetimidate method has been applied to the construction of α-d-galacto- and α-d-glucopyranosides. The readily available β-trichloroacetimidates of 2,3,4,6-tetra-O-benzyl-d-galacto- and glucopyranose (1-β and 3-β, respectively) have been employed in glycosidations with several monosaccharides (either A, B, C or D) under varying experimental conditions. With the galactose derivative 1-β as a donor and each of the monosaccharides A-D as acceptors, the corresponding disaccharides 1A-1D, were obtained in high yield and with good α-stereoselectivity when employing diethyl ether as solvent and either trimethylsilyl- or tert-butyldimethylsilyl trifluoro-methane sulphonate as catalyst. Glycosidations with the glucose derivative 3-β, as donor, and with the monosaccharide acceptors A, B or D, gave the corresponding disaccharides 3A, 3B and 3D, in high yield but with somewhat lower α-diastereoselectivity than observed with the galactose derivative 1-β. The stereochemical outcome of the reactions is rationalised in terms of possible reaction mechanisms.     

Synthesis and study of the cyclization pathways and reactivities of α-diazoimidolates

The reaction of unsymmetrical N,N-disubstituted malonamides with benzenesulfonyl azide in the presence of sodium ethoxide gives individual sodium 1,2,3-triazol-5-olates or mixtures of their isomers, from the relative amounts of which the effect of substituents in the amido groups on the cyclization pathways and reactivities of -diazoimidolates was ascertained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1521–1527, November, 1991.     

Synthesis of α-alkoxyalkyltributyllead compounds via the reaction of tributylplumbyllithium with α-chloroethers,and the conjugate addition of tributylplumbyllithium to enones

α-Alkoxyalkyltributylleads 1 were prepared from the reaction of tributylplumbyllithium with α-chloroethers 2. This procedure is more convenient than the conventional method which involves transmetallation from the corresponding α-alkoxyalkyltrialkyltin. Tributylplumbyllithium was also used for the synthesis of β-oxo-organolead 4.     

Synthesis and structure of cobalt α-dioximate complexes with isonicotinamide

New cobalt trans-dioximate complexes with isoniconinamide have been synthesized: [Co^II(DmgH)₂(Inia)₂] (I), [Co^III(DmgH)₂(Inia)₂][PF₆] · 1.5H₂O (II), [Co^III(NioxH)₂ (Inia)₂][PF₆] · H₂O · CH₃OH (III), and [CoIIICl(DmgH)₂(Inia)] · H₂O (IV), where DmgH⁻ and NioxH⁻ are the dimeth-ylglyoxime and 1,2-cyclohexanedionedioxime monoanions, respectively; Inia is the isonicotinamide molecule. The structures of compounds I–IV have been determined by X-ray crystallography. In I–IV, Co(II) or Co(III) has an octahedral environment with the pseudomacrocyclic (DioxH⁻)₂ moiety (DioxH⁻ is the dioximate monoanion) in the equatorial plane. The latter is stabilized by O-H…O hydrogen bonds. The isonicotinamide molecules in all four complexes are monodentately bound to the metal ion through the heterocyclic nitrogen atom.     

Synthesis of (−)-okundoperoxide and determination of the absolute configuration of natural (+)-okundoperoxide

The first enantioselective synthesis of (3S,4aR,8aR)-1 (the enantiomer of natural okundoperoxide) has been accomplished. The synthesis features: 1) stereoselective installation of the peroxy functionality (16 → 17); 2) ring opening of peroxyacetal and subsequent intramolecular reaction between the hydroperoxide and the vinyl epoxide to form the peroxy six-membered ring (5 → 1). The absolute configuration of okundoperoxide was determined to be 3R,4aS,8aS by comparing specific rotations of the synthetic sample and the natural product.     

The Preparation of α-Phosphonovinylzirconocenes and their Application in the Stereospecific Synthesis of α-Halo-l-alkenylphosphonates

Hydrozirconation of 1-alkylnylphosphonates gives the organozirconium(Ⅳ) complexes 2 in syn-addition way.Complexs 2 was trapped with NCS,NBS or I2 to afford stereodifined α-halo-1-alkenylphosphonates in moderate to high yields.     

Divergent Asymmetric Reactions of ortho-Quinone Methides with α-Thiocyanato Indanones for the Synthesis of Spiro- and Fused-Indanones

Reported in this work is a water triggered chemo-divergent enantioselective spiro-annulation and cascade reaction of ortho-quinone methides (o-QMs) with α-thiocyanato indanones catalyzed by a chiral organic base. In the case of spiro-annulation, the use of trace amount of water as additive is critical to achieve high enantioselectivity (up to 96 % ee). We found that a cascade reaction was enabled by just tuning the ratio of water in solvent. Accordingly, two new highly efficient asymmetric reactions for the divergent synthesis of spiro- and fused-indanone scaffolds with excellent enantioselectivities (up to 99 % ee) were developed. Mechanistic investigations suggest that interfacial hydrogen bonding may play an important role in achieving the switchable reaction pathways.     

Synthesis and evaluation of novel α-aminoamides with substituted benzene scaffold for the treatment of neuropathic pain

Small molecule sodium ion channel blockers with a pharmacophore of α-aminoamide have exhibited anti-allodynia effects on neuropathic pain. A library of new α-aminoamide derivatives containing a scaffold of substituted benzene were designed and synthesized. These compounds were evaluated in mice formalin model and they exhibited significant analgesic activities. However, the anti-allodynia mechanism of these compounds remains unclear; some of the target compounds can only moderately inhibit the sodium ion channel, Nav1.7, in a whole-cell patch clamp assay. These results suggest that introduction of the moiety of substituted benzene to α-aminoamide derivatives can improve their bioactivity and further study is warranted.     

Synthesis of arylglycine and mandelic acid derivatives through carboxylations of α-amido and α-acetoxy stannanes with carbon dioxide

Incorporation reactions of carbon dioxide (CO(2)) with N-Boc-α-amido and α-acetoxy stannanes were developed using CsF as a mild tin activator. Monoprotected α-amido stannanes could be used, and the corresponding arylglycine derivatives were obtained in moderate-to-high yields under 1 MPa (10 atm) of CO(2) pressure. α-Acetoxy stannanes also underwent carboxylation to afford mandelic acid derivatives in excellent yields under ambient CO(2) pressure. Both transformations enabled the synthesis of α-tertiary and α-quaternary carboxylic acid derivatives. In addition, the chirality of (S)-N-tert-butylsulfonyl-α-amido stannanes was transferred with up to 90% inversion of configuration at 100 °C.     

Synthesis of α-galactosyl ceramide analogues with an α-triazole at the anomeric carbon

The synthesis of 1,2,3-triazole containing analogues of α-GalCer and galacturonic acid containing Sphingomonous cell wall antigens is described. Anomerisation was used to provide the required α-glycosyl azide precursor. Copper azide–alkyne cycloaddition (CuAAC) generated the α-triazole linkage.     

Synthesis and Stereochemistry of some New Unsymmetrical Phosphates with α-Poly-fluoroalkylbenzyl Fragments

Abstract

The methods of synthesis unsymmetrical polyfluoroalkyl phosphates (II) by catalytic phosphorylation of phenols or polyfluoroalkanols by chlorophosphates (I) were elaborated     

Synthesis and Characterization of Liquid Crystal with Lower Temperature of Phase Change of meso-tetra-(4-n-lauroyloxyphenyl)porphyrin

Metalloporphyrincomplexeshavebeenextensivelystudiedinmanyfunctionalchemistrytieldssuchasphoto-eletronicconversionnon-linearoptics,biomimeticstudiesandcatalyticefttcts.TOourknowledge,thefirstliquidcrystallineporphyrinwassynthesizedbyGoodbyelall.In1987,Greggetapreportedthesynthesisandtheliquidcrystallinepropertiesofaseriesofporphyrinoctanolesters.In1987,Greggelal3synthesizedoctakis(0-hydroxyethyl)porphyrin.In1991,tetrakis(4-n-lauroylphenyl)porphyrinwaspreparedbyShimizuetal#.In1994,5.15-disubs…     

Synthesis and Reaction of 4-Methyl-3,4-epithiotetrahydropyran with α-Amino Acids

4-Methyl-3,4-epithiotetrahydropyran was synthesized by the recyclization of 4-methyl-3,4-epoxytetrahydropyran by the action of thiourea. The product reacts with -amino acids in an alkaline medium with regioselective opening of the thiirane ring at the least substituted carbon atom.     

Synthesis of α, ω-dihydroxymethylphenylsiloxanes and their reactions with silicon tetrachloride and tetrabutoxytitanium

Russian Chemical Bulletin -     

Synthesis of α-trifluoromethyl-α-hydroxycarboxylate dervatives and their phosphorus-containing analogs with the use of fluorinated diazo compounds

Approach was developed underlain by the use of fluorinated diazocompounds to the synthesis of derivatives of α-trifluoromethyl-α-hydroxycarboxylic acids and their phosphorus-containing analogs, α-trifluoromethyl-α-hydroxyphosphonic acids. Methyl 2-diazo-3,3,3-trifluoropropionate and diethyl 1-diazo-2,2,2-trifluoroethylphosphonate under the action of catalytic quantities of dirhodium tetraacetate Rh₂(OAc)₄ easily inserted into the O-H bond leading to the formation of the corresponding products in high yields.     

A carbon-13 study of relaxation in the mesophases of 5O·7 and the 5CB homologous series

Abstract

Carbon-13 spin-lattice relaxation times of the protonated ring carbons have been measured at 22·6 MHz in the nematic and all four smectic phases of 5O·7 (4-n-pentyloxybenzylidene-4′-n-heptylaniline). Dong has obtained the deuterium spectral densities J ₁ and J ₂ at 15·4MHz for the deuterated aniline ring of 5O·7-d ₄, and has presented and applied a theory in which the spectral densities are expressed in terms of the diffusion constants D∥ and D?. His results are used to calculate ¹³C relaxation times from the spectral densities J ₀, J ₁ and J ₂. The calculated ¹³C spin-lattice relaxation times are then compared with our experimental values to test the theory. The ¹³C spin-lattice relaxation times of all the resolved resonances in the various phases of the first four members of the 5CB homologous series have been published previously. Dong has also published an analysis of 5CB deuterium data, and we use his results for the diffusion constants D∥ and D? to calculate ¹³C relaxation times of the protonated aromatic carbons of 5CB, 6CB, 7CB and 8CB. The ¹³C relaxation times of the unprotonated aromatic carbons of the 5CB series are calculated in the manner of Wittebort et al., but using the spectral density expressions developed by Dong. The calculated ¹³C spin-lattice relaxation times of the 5CB homologous series are then compared with our experimental values to test the theory for the protonated and unprotonated ring carbons.