Study on the α-Thiocarbonylthioformamide Ⅰ-Comparison with α-carbonylthioformamide

α-Carbonylthioformamide 1 and α-thiocarbonylthioformamide 1 were synthesized by Adiwidjaja in 1980¹. However, there is no report of these compounds related their properties and reaction activities². Compound 1 has two possible sites for nucleophilic attack. In our previous works., it was used to synthesize a lot of heterocyclic compounds (Scheme l)^3-6.     

Study of pre-equilibrium effects on α-induced reactions on copper

A stack of natural copper was bombarded with -particles. Cumulative cross-sections for⁶⁵Ga,⁶⁶Ga and⁶⁵Zn production, and the excitation functions for⁶⁸Ga and⁶⁷Ga production, were measured using high resolution gamma-ray spectroscopy. The data are compared with the theoretical result provided by equilibrium and pre-equilibrium reaction model, for this purpose we used the code ALICE of Blann. The overall agreement with theory is good. Besides, we present the experimental data obtained by other authors.     

Functionally substituted dienes based on α-pinene

Dienes containing an -pinene fragment were synthesized from myrtenal and functionally substituted phosphonates. Their structures were studied using¹NMR, IR, Raman, UV, and CD spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1779–1782, October, 1994.     

Study on the Reaction of α-Ketohemithioacetal

Aromatic α-sulfinyl carboxylic acids can be rearranged to hemithioacetals or other derivatives of glyoxylic acid under the action of acid reagents was first reported by Pummerer¹. Later, Russell and coworkers applied this rearrangement to β-ketosulfoxides, synthesized α-ketohemithioacetal², which can be transformed to α-keto alcohol, α-keto aldehyde and α-hydroxy alcohol, α-hydroxy acid³. Furthermore, Hall and Poet reported that α-ketohemithio-acetal can be rearranged to the corresponding α-hydroxythioester in the presence of magnesium nitrate and sodium acetate or tertiary amine⁴. However, few reports of reaction of α-ketohemithioacetal can be seen in literature.     

Study on the Reaction of α-Thiobenzoylthioformylmorpholine

a-ThiocaIbonylthiOformnddesareOfalmostunexploredclassOfcomPOundsll],althoughtheyhavebeenpreParedsincel98Ol2-3].ThisattractSustoexploretheirchendStryandutilityinSynthesisOfheteropcles.Accordingtoourpreviousmethodl`1,a-benzOylthiOfOrmyl-morpholine1wasprePaIedfirst,fOllowedbysumirizationOfcarbonylwithLawessenreagnttoaffordtheexpeCtedcr-thjobenzoylthiOformylmorpholine2,whchhastWothiotnylgrous.onthebasisOfstructUreof2,itcanbereactedwithcomPOundsbearingdrinctionalgrouP,suchasdidrineandsen…     

Synthesis of α-S-glycosphingolipids based on uronic acids

The synthesis of S-glycosphingolipids based on uronic acids is described. These compounds are analogous to the highly immunostimulatory antigens isolated from the cell walls of bacteria of the Sphingomonas family. Key to the synthetic route is a stereoselective anomerization to give α-glycosyl thiol precursors. A route to a sphinganine precursor from pseudoephedrine glycinamide is also described.     

Asymmetric additions of α-sulfoxide carbanion on imines

The formation of the anion of methyl p-tolyl sulfoxide was studied in various experimental conditions. This allowed to get a very good control of diastereoselectivity during addition of the above carbanion on many imines. Various stereoisomerically pure aminosulfoxides have been prepared by this approach.     

Stereoselective Synthesis of α-Aminonitril on Glucose Templates

Both proteinogenic and non proteinogenic α-amino acids are of particular interest as constituents of peptide factors, peptidomimetics and antibiotics for the construction of modern selective drugs. [1] Furthemore, α-amino acid derivatives are interesting building units for chiral-pool syntheses of enantiomerically pure natural products. [2] Numerous efforts in modern organic synthesis are centered on the synthesis of enantiomerically pure α-amino acids. [3] During the past three decades efficient methods of asymmetric synthesis of α-amino acids have been developed; most of them are based on electrophilic transformations of organometallic intermediates. [4] Using the concept that the chirality of the carbohydrates can be exploited for diastereoselective reactions, Kunz and his cooperator had developed a Strecker synthesis with glycosyl amines as chiral auxiliaries. [5]     

Conformational studies on peptides containing α,α-disubstituted α-amino acids: chiral cyclic α,α-disubstituted α-amino acid as an α-helical inducer

Four types of α,α-disubstituted amino acids {i.e., α-aminoisobutyric acid (Aib), 1-aminocyclopentanecarboxylic acid (Ac(5)c), (3S,4S)-1-amino-(3,4-dimethoxy)cyclopentanecarboxylic acid [(S,S)-Ac(5)c(dOM)] and its enantiomer (R,R)-Ac(5)c(dOM)} were introduced into l-leucine-based hexapeptides and nonapeptides. The dominant conformations of eight peptides: Cbz-(L-Leu-L-Leu-dAA)(2)-OMe [dAA = 1: Aib; 2: Ac(5)c; 3: (S,S)-Ac(5)c(dOM); 4: (R,R)-Ac(5)c(dOM)] and Boc-(L-Leu-L-Leu-dAA)(3)-OMe [dAA = 5: Aib; 6: Ac(5)c; 7: (S,S)-Ac(5)c(dOM); 8: (R,R)-Ac(5)c(dOM)], were investigated by IR, CD spectra and X-ray crystallographic analysis. The CD spectra revealed that Aib hexapeptide 1 and Ac(5)c hexapeptide 2 formed right-handed (P) 3(10)-helices, while Ac(5)c(dOM) hexapeptides 3 and 4 formed a mixture of (P) 3(10)- and α-helices. The Aib nonapeptide 5 formed a (P) 3(10)-helix, the Ac(5)c nonapeptide 6 formed a mixture of (P) 3(10)- and α-helices, and the Ac(5)c(dOM) nonapeptides 7 and 8 formed (P) α-helices. X-Ray crystallographic analysis revealed that the Aib hexapeptide 1 formed a (P) 3(10)-helix, while (S,S)-Ac(5)c(dOM) hexapeptide 3 formed a (P) α-helix. In addition, the Ac(5)c nonapeptide 6 and (R,R)-Ac(5)c(dOM) nonapeptide 8 formed (P) α-helices. The Aib and achiral Ac(5)c residues have the propensity to form 3(10)-helices in short peptides, whereas the chiral Ac(5)c(dOM) residues have a penchant for forming α-helices.     

Multitracer study on adsorption of metal ions on α-Fe2O3

pH dependence of the adsorption of Na, Sc, Ga, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, and Pd on -Fe₂O₃ from a 0.1 mol dm^–3 NaCl solution was studied by using a multitracer technique. Desorption of the metal ions from the -Fe₂O₃ with the adsorbed metal ions at pH 11 was also studied by lowering the pH of the suspensions. The desorption curve of each element was in good agreement with the adsorption curve except for Ru and Rh under conditions studied. Adsorption kinetics showed that the adsorption of most metal ions increases with shaking time before an adsorption equilibrium is attained. An increase in the adsorption was also observed with an elevation in temperature for the elements, suggesting that the adsorption is involved in chemisorption.     

Structural intermediates during α-synuclein fibrillogenesis on phospholipid vesicles

α-Synuclein (AS) fibrils are the main protein component of Lewy bodies, the pathological hallmark of Parkinson's disease and other related disorders. AS forms helices that bind phospholipid membranes with high affinity, but no atomic level data for AS aggregation in the presence of lipids is yet available. Here, we present direct evidence of a conversion from α-helical conformation to β-sheet fibrils in the presence of anionic phospholipid vesicles and direct conversion to β-sheet fibrils in their absence. We have trapped intermediate states throughout the fibril formation pathways to examine the structural changes using solid-state NMR spectroscopy and electron microscopy. The comparison between mature AS fibrils formed in aqueous buffer and those derived in the presence of anionic phospholipids demonstrates no major changes in the overall fibril fold. However, a site-specific comparison of these fibrillar states demonstrates major perturbations in the N-terminal domain with a partial disruption of the long β-strand located in the 40s and small perturbations in residues located in the "non-β amyloid component" (NAC) domain. Combining all these results, we propose a model for AS fibrillogenesis in the presence of phospholipid vesicles.     

Study on the Intercalation of TMAPP into α-ZrP

In this paper, an intercalation compound of layered α-ZrP with TMAPP was firstlysy nthesized by using the α-ZrP-BA pre-intercalation compound as intermediate. And wesystemically investigated the intercalation behavior of TMAPP into α-ZrP by XRD, visible spectrum and fluorescence spectrum.     

Amphiphilic α-helix mimetics based on a benzoylurea scaffold

The design and synthesis of amphiphilic benzoylurea α-helix mimetics is described. These conformationally constrained molecules allow for the correct angular and spatial projection of hydrophobic and hydrophilic groups and thus the reproduction of side-chains on both faces of an α-helix.     

Study on the α-ray radiolysis product of hydroxysemicarbazide

Journal of Radioanalytical and Nuclear Chemistry - Hydroxysemicarbazide (HSC) as a novel salt-free organic reductant has the ability to accomplish the reduction of Pu(IV) fast in the nuclear fuel...     

A flow-through enzymatic bioreactor based on immobilized α-chymotrypsin

With the aim to develop a flow-through enzymatic bioreactor based on a macroporous monolithic sorbent, immobilization of chymotrypsin was performed by the reaction of amino groups of the enzyme with epoxy groups of the sorbent. The enzymatic hydrolysis of low- and high-molecular-weight substrates, N-benzoyl-L-tyrosine ethyl ester and human serum albumin, was studied.     

Inhibition of cyclodextrins on the activity of α-amylase

α-amylase activity influences both flour fermentation process and the quality of the fermented products due to its ability of breaking starch into smaller units. The inhibition of cyclodextrins on α-amylase activity was investigated in this paper. Experiment results showed that hydrophobic cavity size was an intrinsic factor during the inhibition processing. Among three types of cyclodextrin (α-, β- and γ-), β-type exhibited the most significant inhibitory activity toward α-amylase. The optimal inhibitory parameters were indicated to be pH 5.9, concentration of β-cyclodextrins 1 mmol/L, reaction temperature 45 °C and reaction time 60 min. Results suggested that the endogenous fluorescence of α-amylase was inhibited by cyclodextrins. Circular dichroism spectrum indicated that the secondary structure of α-amylase, including α-helices, β-sheets and random coils, was changed by cyclodextrins. All the results in this paper aim to provide a further understanding for α-amylase in the industry application.     

Isotherm of α-tocopherol adsorption on acid-activated clinoptilolite tuff

Adsorption of α-tocopherol from ethanol solution on clinoptilolite tuff activated with 4.0 M HCl is studied. α-Tocopherol adsorption isotherm is analyzed using the Langmuir, Freundlich, and Redlich-Peterson adsorption theories. The adsorption of α-tocopherol from dilute solutions on this sorbent is ascertained to be described by the Langmuir model.     

Studies on Fragrance Raw Materials of α-Terpineol Analogues

Thirty four α-substituted or α, α-disubstituted-( 1-methylcyclohexen-4-yl )methanols and α-substituted or α,α-disubstituted-(4-methylcyclohexyl) methanols weresynthesized. Thirty two of them are new compounds. 1H NMR and IR spectra of allthe compounds were determined, MS spectra of some of them were obtained as well.The characteristic odors were evaluated.Keywords Fragrance raw materials,α-Terpineol analogues, Synthesis, Structuredetermination