A Convenient Synthesis of β-Ketosulfoxides

β-Ketosulfoxideshaveattractedmanyorganicchemistsbecauseoftheirwideuseinsynthesisofketones,a-ketols,glyoxals,a-ketoacids,glycols,a-hydroxyacidsandsoculGenerally,6-ketosulfoxidescanbepreparedbythereactionofesterwithsulfoxidel',acylchloridewithsulfoxi...     

The design and synthesis of a novel organophosphorus compound containing the structure of both β-amino acid and β-aminophosphonate

<正>A novel organophosphorus compound containing the structure of bothβ-amino acid andβ-aminophosphonate is designed and synthesized.Arbuzov reaction with P(OEt)_3,the N-Boc protected iodide 3 cannot provide the desired product but 2-oxazolidinone 4 because of the neighboring-group participation of the Boc moiety.To avoid the intramolecular participation of the carbamates,the Ts protecting group is employed and the Ts-protected iodide 5 affords the target product successfully.     

Structure determination of glycopeptide of β-momorcharin

The structure of the N-linked oligosaccharide chain of β-momorcharin, a ribosome-inactivating protein from the seeds of Momordica charantia Linn (Cucurbitaceae), was determined. A glycopeptide liberated by pronase digestion of the glycoprotein was subjected to amino acid and neutral carbohydrate analysis to establish the composition of amino acid and sugar residues. The sequences and glycosylation hnkages of the sugar and amino acid residues in the glycopeptide were determined as Manαl-6(XyIβ1-2)-Manβ1-4GlcNAcβ1-4(Fucαl-3)-GlcNAc-Asn-Leu by 2D-NMR spectroscopy and FAB-MS data.     

Novel Method for the Enantioselective Synthesis of β-Lactams

A novel method for the enantioselective synthesis of β-lactams is described in this study.2,3-Dihydrobenzooxazin-4-one derived from salicylamide and L-menthone was used as the chiral auxiliary, which reacted with α-bromo-acyl bromides in the presence of pyridine to give carboximides 2. The stereo-controlled Reformatsky-type reactions of carboximides with imines yielded the corresponding trans β-lactams with high enantioselectivities(e.e. 75%-86%) and high chemical yields(63%-85%), meanwhile, the chiral auxiliary dihydrobenzooxazin-4-one was released and recovered.     

Diastereoselective α-Alkylation of β-Amino Esters: Preparation of Novel α-Substituted β-Amino Esters from α-Amino Acids

b-Amino acids and their derivatives have attracted considerable attention in recent years due to their occurrence in biologically active natural products, such as dolastatins 11, cyclohexylnorstatine 22 and taxol 33. bAmino acids also find application in the synthesis of blactams4, piperidines5, indolizidines6. Moreover, the peptides consisting of bamino acids, the so called bpeptides, have been extensively studied recently7. Consequently, considerable efforts have been directed to the synt…     

Synthesis of β-Cyclodextrin Bonded Metal Porphyrins

InrecentyearsstUdyondevelopingnovelmimicenZymemodelsthathavebothoNOO-decomPositionandO,'(or.OH)dismutaseabilityisaveryactiveresearchfield1'2.Thesemodelsshowverytwrtanteffectinprovidingprotectionfromtissuedamageassociatedwithvariousmpesofinfiammatorydiseases.MetallopoIPhyrinsassuPeroxidedismutase(SOD)mimicshaveshowedtheabilitytocatalysttheseharmfulradicals.Groveandco-workersrePorted[Mn(III)TMPyP]and[Fe(III)TMPyP]whichhaveshowedveryefficientbehaviorasperoxynitritereductaseandcandep…     

Photoinitiated Reaction of β-Bromonaphthalene with Pinacolone Ion in DMSO

The radical nucleophilic substitution reaction (SRN1) has been studied widely. The reaction has constituted an important synthetic possibility to achieve substitution of different substrates with different nucleophiles1-3. The main steps of the reaction process are presented in Scheme 1.Scheme 1. Pinacolone enolate ions are widely used as nucleophiles within SRN1reaction 4-6 because it can introduce six carbon atoms into substitution products. In the paper, the photoinitiated reaction of …     

Selective Modification of β-Cyclodextrin on the Secondary Side 4:Preparation of Arylated β-Cyclodextrins with a Flexible Chain

Cyclodextrins(CDs,includinga-,o-,a-CD,etc.)havegainedprominenceinrecentyearsbecauseoftheirtorus-shapedcavity,whichishydrophilicoutsideandhydrophobicinside,caPableofprovidingidealprototypestoconstructefficientartificialenzymes,molecuIarrecognitionsensorsandotherfunctionalmodels.l-3Forbuildingmoreefficientartificialenzymesandmolecularrecognitionsensors,wehavepreparedaseriesof6-CDderivativesbearingchromophores'-'andfoundthat3"-'anarylmoietycouldactasaspectrometryprobeaswellasafunctionalgroup.F…     

A Computational Study on Water-assisted Ammonolysis of N-Methyl β-Sultam

The ring opening of β-sultam via an H2O-assisted ammonolysis process was studied by using Density Functional Theory(DFT) method at the B3LYP/6-31G* level as a further step in the theoretical investigation of the ammonolysis reaction of β-sultams. The calculated pathways are analogous to those previously described for the non-assisted ammonolysis reaction. Solvent effects were assessed by using the polarized continuum model(PCM) method. The results show that mode 1 and pathway a in channel Ⅱ are the most favorable ones in both the cases. The energy barrier of the cleavage of C-S bonds producing P1 is the highest among all the energy barriers. The presence of a solvent in the continuum model disfavors the reaction, whereas the participation of water in the ammonolysis reaction plays a positive role and reduces the active energy greatly. The relative energies of all the transition states in the assisted ammonolysis are 20-80 kJ/mol lower than those for the non-assisted reaction.     

Silicon mediated synthesis and selected transformations of β-chloroketones

A combination of tetrachlorosilane（TCS） and phenol in dichloromethane was found to be an efficient reagent for hydro-chlorination ofα,β-unsaturated ketones to afford the correspondingβ-chloroketones in good yield at ambient temperature. Reactions of the titled compounds with TCS-NaN₃ as well as with nitriles utilizing TCS-ZnCl₂ to give 1,5-disubstituted tetrazole derivatives orβ-amido ketones respectively are also described.     

Synthesis and Stereostructure of New β-Lactam Derivatives of1,5-Benzothiazepines

Becauseoftheimportanceofbenzothiazepinederivatives,whichexhibitversatilebiologicalactivities.thechemistryofbenzothiazepinehasarousedinterestforalongtime'-'.Inourpreviouspapers.wehavereportedthesynthesisandelucidationofthestereostructureoftwokindsofl,5-benzothiazepine-6-lactams'-'.InordertoelucidatetheinfluenceofthesizeofthesubstituentatC-2ontheconfigurationof0-lactammoietyandfurtherstudythestereochemistryofthecycloadditionreaction.wepreparedaseriesofnewfi-lactamderivativesofI.5-benzothiazepine…     

Kinetics of Catalytic Hydrolysis of Potato Starch by Immobilized β-Amylase

The enzyme activity of immobilized β-amylase carried on active carbon and the reaction kinetics for hydrolysis of potatostarch catalyzed by the enzyme have been investigated. A kinetics model based on the overall reaction has been suggested and a reaction coefficient as a new parameter introduced. All of the kinetics parameters involved in the model, including the reaction coefficient, reaction order rate constant as well as the maximum reaction rate etc. at different temperatures have been obtained by using the modified Quasi-Newton optimization technique.     

Synthesis of new chiral 1,2,3,4-tetrahydroisoquinoline β-amino alcohols from L-DOPA

Four new chiral 1,2,3,4-tetrahydroisoquinoline-derived β-amino alcohols were synthesized from L-DOPA in good yields.The structures of the target compounds were confirmed by 1H NMR,13C NMR and MS.     

PMA-SiO2 catalyzed synthesis of β-keto enol ethers

An efficient conversion of β-diketones into correspondingβ-keto enol ethers with catalytic amount of PMA-SiO_2 has been achieved.     

In vitro digestibility of soybean β-conglycinin hydrolysates

The in vitro digestibility of alcalase enzymatic hydrolysates ofβ-conglycinin was studied.The results showed that the zeta potentials ofβ-conglycinin hydrolysates decreased and their electronegativity increased when digested with pepsin and trypsin.Furthermore,the content of peptides with molecular weight from 10 kDa to 20 kDa remained stable,while those with higher molecular weight(>20 kDa) decreased,and those with lower molecular weight(<10 kDa) increased.The proportion of highly hydrophobic peptides decreased in the process of the in vitro digestion,but no significant change in the surface hydropliobicity indices of digestion products was observed(P<0.05).These results indicate that theβ-congiycinin hydrolysates were degraded through in vitro digestion,but the degree of degradation was relatively low.Peptides with molecular weight from 10 kDa to 20 kDa in theβ-conglycinin hydrolysates resisted the digestion by pepsin and trypsin and they remained stable during the in vitro digestion processes.     

Synthesis of Substituted 3H-Indole-modified β-Cyclodextrin

Substituted 3H-indole modified β-cyclodextrin (β-CD) was prepared by the reaction of 6-deoxy-6-[(2-aminoethyl)amino]-β-CD (CDen) with 2-[(p-amino)phenyl]-3, 3-dimethyl-5-car-boxyl-3H-indole (substituted 3H-indole) in the presence of dicyclohexylcarbodiimide (DCC) and 1-hydroxybenzotriazole (HOBt). The product has been characterized by means of elementalanalysis, MS and ^1H NMR.     

Synthesis of a new Class of Chiral β—Mercaptoalcohols from Amino Acids

The syntheses of three new optically active β-mercaptoalcohols,(R)-1,1-diphenyl-2-mercapto-3-methyl-1-butanol,(R)-1,1-diphenyl-2-mercapto-4-methyl-1-pentanol,and (R)-1,1-diphenyl-2-mercapto-1-benzenepropanol from the corresponding amino acids are described.The enantiomeric excesses of these β-mercaptoalcohols were determined by ^1H NMR as their (S)-mandeloyl derivatives.     

Extraction and Crystal Structure of β-Sitosterol

The title compound β-sitosterol(C29H50O), an active phytosterol in many medicinal and edible plants, was characterized by X-ray diffraction analysis and extensive nuclear magnetic resonance(NMR) data. It crystallizes in monoclinic system, space group P21 with C29H50O·1/2H2O, a = 9.4226(7), b = 7.4824(9), c = 36.889(3) , V = 2597.0(4) 3, Z = 4, Dx = 1.084 g/cm3, Mr = 423.70, F(000) = 948, and μ = 0.064 mm-1. The final R = 0.0886 and wR = 0.2234 for 10157 observed reflections(I 2σ(I)). The molecular crystal structure of β-sitosterol shows relative stereochemistry of 24R-ethylcholest-5-en-3β-ol. The molecule is composed of one steroid nucleus(3 six-membered rings and 1 five-membered ring) and one sidechain of 10 carbons. There are two C29H50O molecules and one H2O molecule in a symmetrical unit, and the title compound is stacked into a special laminated structure through hydrogen bonds and van der Waal forces. The special laminated structure was first reported.     

Growth of ZSM-5 crystals within hollow β-zeolite

A zeolite composite composed of ZSM-5 andβ-zeolites has been synthesized by a procedure of the nucleation and crystallization of ZSM-5 zeolite in the hollowβ-zeolite.The property ofβ-zeolite crystals with aluminum-poor interior and aluminum-rich outer rim results in silicon extraction favorably in the aluminum-poor bulk rather than the aluminum-rich external surface.Subsequently,alkaline treatment ofβ-zeolite crystals during the second-step synthesis leads to a preferential dissolution of the aluminum-poor center and the formation of hollowβ-zeolite crystals.ZSM-5 zeolite crystals are therefore embedded and grown within the hollowβ-zeolite.The catalytic activities of Co-Hβ,Co-HZSM-5 and Co-HZSM-5/BEA are investigated during the reaction of methane catalytic reduction NO in the presence of O₂.     

Adsorption separation of carbon dioxide, methane, and nitrogen on Hβ and Na-exchanged β-zeolite

Adsorption isotherms of carbon dioxide (CO2), methane (CH4), and nitrogen (N2) on Hβ and sodium exchanged β-zeolite (Naβ) were volumetrically measured at 273 and 303 K. The results show that all isotherms were of Brunauer type Ⅰ and well correlated with Langmuir-Freundlich model. After sodium ions exchange, the adsorption amounts of three adsorbates increased, while the increase magnitude of CO2 adsorption capacity was much higher than that of CH4 and N2. The selectivities of CO2 over CH4 and CO2 over N2 enhanced after sodium exchange. Also, the initial heat of adsorption data implied a stronger interaction of CO2 molecules with Na+ ions in Naβ. These results can be attributed to the larger electrostatic interaction of CO2 with extraframework cations in zeolites. However, Naβ showed a decrease in the selectivity of CH4 over N2, which can be ascribed to the moderate affinity of N2 with Naβ. The variation of isosteric heats of adsorption as a function of loading indicates that the adsorption of CO2 in Naβ presents an energetically heterogeneous profile. On the contrary, the adsorption of CH4 was found to be essentially homogeneous, which suggests the dispersion interaction between CH4 and lattice oxygen atoms, and such interaction does not depend on the exchangeable cations of zeolite.