Total synthesis of amphidinolide E

A convergent and highly stereocontrolled synthesis of amphidinolide E (1) has been accomplished. The synthesis features a highly diastereoselective (>20:1) BF3.Et2O promoted [3+2] annulation reaction between aldehyde 3 and allylsilane 4 to afford substituted tetrahydrofuran 2.     

Synthesis of 2(3H)-furanones via electrophilic cyclization

A variety of highly substituted 2(3H)-furanones are readily prepared from 3-alkynoate esters and the corresponding acids via electrophilic cyclization. Successful electrophiles in this process include I2, ICl, and PhSeCl. This highly efficient process proceeds under mild conditions, tolerates various functional groups, and generally provides substituted 2(3H)-furanones in good to excellent yields.     

Synthesis and Diels-Alder reactions of 2-alkyl-5-methylene-1,3-dioxolan-4-ones and 2-alkyl-3-acyl-5-methylene-1,3-oxazolidin-4-ones: Highly exo and diastereoface selective chiral ketene equivalents

Chiral dienophiles 1–3 undergo highly exo and diastereoface selective Diels-Alder reactions. The Diels-Alder reactions of 3 are also highly exo selective under Lewis acid catalyzed conditions.     

Direct stereocontrolled synthesis of 3-amino-3-deoxy-beta-mannopyranosides: importance of the nitrogen protecting group on stereoselectivity

The highly stereocontrolled synthesis of the 3-amino-3-deoxy-beta-mannopyranosides is achieved by means of thioglycoside donors protected with a 4,6-O-benzylidene or alkylidene acetal and a benzylidene imine group. Among the various nitrogen protecting groups investigated only the Schiff's base was found to give high beta-selectivity. N-Phthalimido and N-acetamido protected donors were found to be highly alpha-selective, whereas 3-azido-3-deoxy glycosyl donors gave intermediate selectivity. The reasons for the protecting group dependency are discussed in terms of the change in the O2-C2-C3-N3 torsional interaction on conversion of the covalent glycosyl triflates to the transient oxacarbenium ions.     

One pot,three component 1,3 dipolar cycloaddition: Regio and diastereoselective synthesis of spiropyrrolidinyl indenoquinoxaline derivatives

A competent and highly discriminating one-pot synthesis of highly diversified novel functionalized indenoquinoxalone grafted spiropyrrolidine linked chromene-3-carbonitrile conjugates accumulating three pharmocophoric cores, heterocyclic indenoquinoxalone, pyrrolidines and chromene-3-carbonitrile in a single molecular framework by means of 1,3-dipolar cycloaddition reaction between indenoquinoxalone, proline/benzyl amine and chromene-3-carbonitrile in ethanol under classical and microwave conditions is described. The three component 1,3-dipolar cycloaddition reaction proceeds via in situ generation of azomethine ylides by the decarboxylative condensation of indenoquinoxalone with proline/benzyl amine and their selectivity towards the endo cyclic double bonds of dipolarophile (chromene-3-carbonitrile) leading to the formation of highly functionalised regio- and diastereoselective molecular hybrids. This methodology exemplifies the green chemistry protocol such as mild reaction conditions, high yields, one-pot procedure and operational simplicity.     

基于香豆素与胍的荧光探针的合成及对Co2+、Fe3+的识别研究(英文)

本论文设计合成了基于1,3-二氨基胍盐酸盐、氨基胍盐酸盐的新型香豆素类荧光探针L1、L2。通过紫外-可见、荧光光谱的变化研究探针L1、L2对金属离子的识别效应。利用Job’s plot曲线确定探针L1与Co²⁺形成了1∶2的配合物,探针L2和Fe³⁺形成了3∶1的配合物,且表现为明显的荧光增强。探针L1对Co²⁺的检出限可达到10^-6mol/L,探针L2对Fe³⁺的检出限可达到10^-7mol/L。两种高灵敏度荧光探针有望应用于生物和环境监测领域。     

Enantioseparation of chiral N-imidazole derivatives by electrokinetic chromatography using highly sulfated cyclodextrins: mechanism of enantioselective recognition

Baseline separation of ten new substituted [1-(imidazo-1-yl)-1-phenylmethyl)] benzothiazolinone and benzoxazolinone derivatives, with one chiral center, was achieved by CD-EKC using highly sulfated CDs (alpha, beta, gamma highly S-CDs) as chiral selectors. The influence of the type and concentration of the chiral selectors on the enantioseparations was investigated. The highly S-CDs exhibit a very high enantioselectivity power since they allow excellent enantiomeric resolutions compared to those obtained with the neutral CDs. The enantiomers were resolved with analysis times inferior to 2.5 min and resolution factors R(s) of 3.73, 3.90, 1.40, and 4.35 for compounds 1, 2, 3, and 5, respectively, using 25 mM phosphate buffer at pH 2.5 containing either highly S-alpha-CD, highly S-beta-CD, and highly S-gamma-CD (3 or 4% w/v) at 298 K, with an applied field of 0.30 kV/cm. The determination of the enantiomer migration order for the various analytes and the study of the analyte structure-enantioseparation relationships display the high contribution of the interactions between the analytes phenyl ring and the CDs to the enantiorecognition process. The thermodynamic study of the analyte-CD affinities permits us to improve our knowledge about the enantioseparation mechanism.     

Synthetic studies on taxol: highly stereoselective construction of the taxol C-ring via SN2' reduction of an allylic phosphonium salt

[reaction: see text] The highly stereoselective construction of the C3 stereogenic center of the taxol C-ring is described. The trans isomer at the C3-C8 position of the taxol C-ring, which is required for the total synthesis, as well as its diastereomeric cis isomer were successfully synthesized with highly diastereoselective S(N)2' reduction of the allylic phosphonium salts.     

Total synthesis of +-superstolide A

A convergent and highly stereocontrolled synthesis of +-superstolide A (1) has been accomplished. Key steps of this synthesis include the intramolecular Suzuki reaction of 26 and the highly diastereoselective transannular Diels-Alder cyclization of macrocyclic octaene 3.     

One-step nanocasting synthesis of highly ordered single crystalline indium oxide nanowire arrays from mesostructured frameworks

A one-step nanocasting route has been demonstrated to prepare highly ordered single-crystal indium oxide nanowire (IONW) arrays with mesostructured frameworks. Unlike the reported multistep nanocasting process (synthesis of mesoporous materials, and then incorporation of precursors and formation of inorganic frameworks), a highly ordered mesostructured surfactant-silica monolith with low external surface serves as both the template and the reducing agent and makes the formation of single-crystal IONWs in its channels easily in one step by using normal In(NO(3))(3) as an inorganic precursor. After silica is removed, highly ordered uniform single-crystal IONW arrays with hexagonal (p6mm) or cubic (Ia3d) mesostructures are derived. These new materials are studied by XRD, SEM, TEM, N(2) adsoption, and UV spectrum. Furthermore, this one-step nanocasting synthesis route is a generalized method and can be used to synthesized a highly ordered mesoporous silica monolith with metal oxide nanocrystals in its channels. To the best of our knowledge, this is the first report of a single crystalline mesostructured In(2)O(3) framework.     

Three-component tandem reaction involving acid chlorides, terminal alkynes, and ethyl 2-amino-1H-indole-3-carboxylates: synthesis of highly diversified pyrimido[1,2-a]indoles via sequential Sonogashira and [3+3] cyclocondensation reactions

A simple, highly efficient three-component reaction involving acid chlorides, terminal alkynes, and ethyl 2-amino-1H-indole-3-carboxylates, for the synthesis of highly diversified pyrimido[1,2-a]indoles has been described. The salient feature of the reaction involves sequential Sonogashira and [3+3] cyclocondensation reactions.     

Stereoselective Substrate‐Controlled Asymmetric Syntheses of both 2,5‐cis‐ and 2,5‐trans‐Tetrahydrofuranoid Oxylipids: Stereodivergent Intramolecular Amide Enolate Alkylation

The concise, highly stereoselective, substrate‐controlled asymmetric total syntheses of both 2,5‐cis‐ and 2,5‐trans‐tetrahydrofuranoid nematocidal oxylipids from the Australian brown algae Notheia anomala have been accomplished in a stereodivergent fashion. The highly stereoselective intramolecular amide enolate alkylation strategy provides access to both stereoisomers of the 3‐hydroxy‐2,5‐disubstituted tetrahydrofuran core of these marine natural products through chelate and nonchelate control, which is driven by the C3‐hydroxy protecting group. This approach offers an optional and highly stereoelective access to any of the eight possible stereoisomers of the 2,5‐disubstituted‐3‐oxygenated tetrahydrofuran skeleton, an important structural feature which is present in many biologically active natural products.     

Organocatalytic asymmetric synthesis of substituted 3-hydroxy-2-oxindoles via Morita-Baylis-Hillman reaction

We report a highly enantioselective Morita-Baylis-Hillman (MBH) reaction of isatins and acrolein to provide enantiomerically enriched 3-substituted 3-hydroxyoxindoles, which could serve as valuable synthetic building blocks. This is also the first time that a ketone has been used as the electrophile and acrolein as the nucleophile in a highly enantioselective catalytic asymmetric MBH reaction. Hatakeyama's catalyst, β-isocupreidine (1), turned out to be a powerful catalyst for this transformation.     

Nitrile and amide biotransformations for the synthesis of enantiomerically pure 3-arylaziridine-2-carboxamide derivatives and their stereospecific ring-opening reactions

Catalyzed by Rhodococcus erythropolis AJ270 (whole cell catalyst) under very mild conditions, a number of racemic trans-3-arylaziridine-2-carbonitriles and amides were efficiently transformed into enantiopure 2R,3S-3-arylaziridine-2-carboxamides. While the nitrile hydratase exhibits low selectivity against nitrile substrates, the amidase is highly enantioselective toward 2S,3R-3-arylaziridine-2-carboxamides. Upon the treatment with catalytic hydrogenation, amine, or water in the presence of one equivalent of TFA, the resulting aziridine-2-carboxamides underwent highly efficient and stereospecific ring-opening reactions to produce enantiopure alpha-amino-, alpha,beta-diamino-, and alpha-amino-beta-hydroxy-propanamide derivatives in high yields.     

Remarkable salt effect on In-mediated allylation of N-tert-butanesulfinyl imines in aqueous media: highly practical asymmetric synthesis of chiral homoallylic amines and isoindolinones

A highly practical and efficient asymmetric synthesis of chiral homoallylic amines by In-mediated allylation of chiral N-tert-butanesulfinyl imines in aqueous media at room temperature was developed. With 2-formylbenzoate imine substrates, the method allows the highly enantioselective achievement of a variety of pharmacologically important 3-allyl isoindolinone compounds.     

A totally stereocontrolled route to N-methyl-γ-amino-β-hydroxy acids: Asymmetric synthesis of the amino acid component of hapalosin

A new approach to the synthesis of N-methyl-γ-amino-β-hydroxy acids, compounds that are essential components of several depsipeptides exhibiting highly interesting therapeutic profiles, is presented. Relevant steps in the synthetic sequence involve the totally stereoselective preparation of a protected aminoalkyl epoxide from a highly enantiopure 2,3-epoxy alcohol, efficient N-methylation and three-step conversion to the desired N-methyl amino acid. The method is exemplified by the enantioselective synthesis of (3R,4S)-4-(N-methylamino)-3-hydroxy-5-phenylpentanoic acid in two differently protected forms.     

钾负载量对CuO/K_2CO_3/MgAl_2O_4催化剂高温NO_x储存还原性能的影响

制备了适用于高温氮氧化物储存还原(NSR)反应的Cu O/K_2CO_3/MgAl_2O_4非贵金属催化剂,考察了钾负载量对催化剂NSR性能的影响,发现钾主要以高分散K_2CO_3和体相K_2CO_3的形式存在.在稀燃条件下,NOx在体相K_2CO_3上形成了高温稳定的硝酸盐物种,而高分散K_2CO_3上形成的硝酸盐的高温稳定性则较差.当钾负载量较低时,催化剂的NOx储存能力有限,K_2CO_3主要以高分散形式存在,稀燃阶段形成的硝酸盐的热稳定性较低,高温NSR活性较低;而钾负载量过高时,K_2CO_3则会覆盖Cu O活性位,从而降低催化剂的NSR活性.在450℃的高温条件下,钾负载量为10%时,所制备催化剂的NOx储存还原能力最佳,NOx还原效率达到99.9%,是一种具有潜在应用前景的高温NSR催化剂.     

Highly Efficient CH Hydroxylation of Carbonyl Compounds with Oxygen under Mild Conditions

A transition‐metal‐free Cs₂CO₃‐catalyzed α‐hydroxylation of carbonyl compounds with O₂ as the oxygen source is described. This reaction provides an efficient approach to tertiary α‐hydroxycarbonyl compounds, which are highly valued chemicals and widely used in the chemical and pharmaceutical industry. The simple conditions and the use of molecular oxygen as both the oxidant and the oxygen source make this protocol very environmentally friendly and practical. This transformation is highly efficient and highly selective for tertiary C(sp³)? H bond cleavage.     

Synthesis of highly functionalized 2(1H)-pyrazinone 3-carboxamide scaffolds

Synthesis of highly functionalized 2(1H)-pyrazinone 3-carboxamide derivatives is reported. A one-pot, two-step process including the base-mediated reaction of N,N-disubstituted aminoacetonitrile derivatives 18 with 3,5-dihalo-2(1H)-pyrazinones 1 afforded substituted aminoacetonitrile pyrazinone derivative 19, which on subsequent oxidation followed by transamidation of the resulting intermediate with primary or secondary amines gave the corresponding highly functionalized 2(1H)-pyrazinone 3-carboxamide derivatives 21.     

Highly Efficient C?H Hydroxylation of Carbonyl Compounds with Oxygen under Mild Conditions

A transition‐metal‐free Cs₂CO₃‐catalyzed α‐hydroxylation of carbonyl compounds with O₂ as the oxygen source is described. This reaction provides an efficient approach to tertiary α‐hydroxycarbonyl compounds, which are highly valued chemicals and widely used in the chemical and pharmaceutical industry. The simple conditions and the use of molecular oxygen as both the oxidant and the oxygen source make this protocol very environmentally friendly and practical. This transformation is highly efficient and highly selective for tertiary C(sp³) H bond cleavage.