Modular Synthesis of a Tridecasaccharide Motif of Bacteroides vulgatus Lipopolysaccharides against Inflammatory Bowel Diseases through an Orthogonal One-Pot Glycosylation Strategy

Lipopolysaccharides from Bacteroides vulgatus represent interesting targets for the treatment of inflammatory bowel diseases. However, efficient access to long, branched and complex lipopolysaccharides remains challenging. Herein, we report the modular synthesis of a tridecasaccharide from Bacteroides vulgates through an orthogonal one-pot glycosylation strategy based on glycosyl ortho-(1-phenylvinyl)benzoates, which avoids the issues of thioglycoside-based one-pot synthesis. Our approach also features: 1) 5,7-O-di-tert-butylsilylene-directed glycosylation for stereoselective construction of the α-Kdo linkage; 2) hydrogen-bond-mediated aglycone delivery for the stereoselective formation of β-mannosidic bonds; 3) remote anchimeric assistance for stereoselective assembly of the α-fucosyl linkage; 4) several orthogonal one-pot synthetic steps and strategic use of orthogonal protecting groups to streamline oligosaccharide assembly; 5) convergent [1+6+6] one-pot synthesis of the target.     

An Improved Procedure for Aryne Generation from o-Triazenylarylboronic Acids through One-Pot Boronate Formation/Silica Gel Treatment

We have developed an improved method for generating aryne from o-triazenylarylboronic acids. Unlike the previous method that required excess o-triazenylarylboronic acids as aryne precursors, we used corresponding boronates as limiting reagents, which resulted in high yields. By combining the formation of boronates and aryne generation through silica gel treatment in one-pot, we were able to effectively use a wide range of o-triazenylarylboronic acids in reactions with various arynophiles. This one-pot method was particularly suitable for transforming complex aryne precursors with different functional groups.     

Synthesis of Lignans Based on a Borate-mediated One-pot Sequential Suzuki-Miyaura Coupling of Cyclic Boranes

Lignans are a group of polyphenolic phytochemicals that possess a large spectrum of chemical structures and biological activities. Here the syntheses of lignans – anwulignan, burseran, dehydroxycubebin, ruburisandrin B, and sesamin – are achieved based on a borate-mediated one-pot sequential Suzuki-Miyaura coupling of cis- and trans-fused bicyclic boranes, which were prepared by diastereoselective cyclic hydroboration of exo-cyclic diene with cyclopentyl- and thexylboranes, respectively. A one-pot sequential Suzuki-Miyaura coupling of each cyclic borate with various aryl bromides initiated by activation of the cyclic borane with the carbon nucleophile provided 2,3-dibenzylbutane derivatives with different aromatic substituents. Finally, the syntheses of naturally occurring lignans were accomplished in several steps from the products of Suzuki-Miyaura coupling.     

Modular Synthesis of Nona-Decasaccharide Motif from Psidium guajava Polysaccharides: Orthogonal One-Pot Glycosylation Strategy

The synthesis of long, branched, and complex carbohydrate sequences remains a challenging task in chemical synthesis. Reported here is an efficient and modular one-pot synthesis of a nona-decasaccharide and shorter sequences from Psidium guajava polysaccharides, which have the potent α-glucosidase inhibitory activity. The synthetic strategy features: 1) several one-pot glycosylation reactions on the basis of N-phenyltrifluoroacetimidate (PTFAI) and Yu glycosylation to streamline the chemical synthesis of oligosaccharides, 2) the successful and efficient assembly sequences (first O3′, second O5′, final O2′) toward the challenging 2,3,5-branched Araf motif, 3) the stereoselective 1,2-cis-glucosylation by reagent control, and 4) the convergent [6+6+7] one-pot coupling reaction for the final assembly of the target nona-decasaccharide. This orthogonal one-pot glycosylation strategy can streamline the chemical synthesis of long, branched, and complicated carbohydrate chains.     

Divergent Total Syntheses of (+)-Vulgarisins A–E

The asymmetric total syntheses of (+)-vulgarisins A–E, which share a rare and highly oxygenated [5-6-4-5] tetracyclic core structure that were isolated from P. vulgaris Linn., have been described for the first time in a divergent manner. Key transformations include: 1) a catalytic asymmetric intramolecular cyclopropanation to forge the A ring bearing desired stereochemistry at C14; 2) a one-pot borylation/conjugate addition process for creation of the C1−C11 bond; 3) a Wolff ring contraction to assemble the bicyclo[3.2.0]heptane subunit (CD rings); and 4) a stereocontrolled pinacol cyclization for construction of the central B ring of the natural products.     

Synthesis and Monoamine Oxidase Inhibitory Activity of 3-Substituted 5H-Indeno[1,2-c]pyridazines

The one-pot synthesis of nine 5H-indeno[1,2-c]pyridazines is described. These compounds are shown to be potent, reversible inhibitors of monoamine oxidase B (MAO-B) with little or no effect on monoamine oxidase A (MAO-A). Qualitative structure-activity relations indicate that the MAO-B inhibitory activity is strongly influenced by electronic and bulk properties of substitutents.     

Aminierende reduktive Kupplung aromatischer Aldehyde mit niervalenten Titan-Reagenzien zu 1,2-Diarylethylendiaminen

Preparation of 1,2-Diarylethylenediamines by Aminative Reductive Coupling of Aromatic Aldehydes with Low-Valent Titanium Reagents In a novel McMurry- Type one-pot reaction, aromatic aldehydes and secondary amines are poupled of give the N, N, N′, N′-tetraalkyl-1,2-diarylethylendiamines 1–22 (Table 3). To this end, a lithium dialkylamide is added to an aromatic aldehyde to give the adduct B which is then treated with 1 equiv. of TiC1₄ to yield a coloured suspension of a reagent synthetically equivalent to a iminium salt ( C/D in Scheme 4). After treatment with a low-valent Ti reagent which is prepared by reduction of TiC1₄ with either K or, preferably, Mg, the coupling products are isolated in 23 to 81% yield as a 1:1 mixture of the diastereoisomers (meso- and rac-form). These are separated either by chromatography or by crystallization and characterized.     

Alloyed (ZnS)x(CuInS2)1−x Semiconductor Nanorods: Synthesis,Bandgap Tuning and Photocatalytic Properties

Rod-like nanocrystals of the semiconductor alloy (ZnS)_x(CuInS₂)_1−x (ZCIS) have been colloidally prepared by using a one-pot non-injection-based synthetic strategy. The ZCIS nanorods crystallize in the hexagonal wurtzite structure and display preferential growth in the direction of the c axis. The bandgap of these quarternary alloyed nanorods can be conveniently tuned by varying the ratio of ZnS to CuInS₂. A non-linear relationship between the bandgap and the alloy composition is observed. The ZCIS nanorods are found to exhibit promising photocatalytic behaviour in visible-light-driven degradation of Rhodamine B.     

A Simple Procedure for Preparing Annulated p-Benzoquinones. Improved Synthesis of 1,4-Dihydro-1,4-methanonaphthalene-5,8-dione

A simple and efficient two-step, one-pot synthesis of substituted 1,4-dihydro-1,4-methanonaphthalene-5,8-diones is reported. This synthesis, which utilizes readily available starting materials and inexpensive reagents, can be used to prepare 1a-1c in 70–90% overall yield. This procedure was extended successfully to prepare a more highly complex annulated p-benzoquinone i.e., 8.     

Pyridine-2(1H)-thiones: Versatile precursors for one-pot synthesis of new nicotinonitrile-thiazole hybrids

In the current study, we report a facile procedure for the preparation of a new series of nicotinonitrile-thiazoles, in excellent isolated yields. For this purpose, pyridine-2(1H)-thiones were investigated as key building blocks for the synthesis of new nicotinonitrile-linked 2-hydroxybenzaldehyde derivatives. To prepare the target thiazole hybrids, a facile one-pot procedure was developed involving amine-mediated reaction of the prior aldehydes, thiosemicarbazide, and the appropriate of hydrazonyl chlorides. The reaction conditions of this one-pot protocol were optimized by repeating the reaction using different solvents and amines. The optimized conditions were conducting the reaction in dioxane containing triethylamine at 100°C for 5 h. The prior protocol gave, in each case, new series of nicotinonitrile-linked thiazole and thiazol-4(5H)-one hybrids, bearing aryldiazenyl or arylhydrazineylidene units. Repeating the prior one-pot protocol using the appropriate halogen containing reagents instead of hydrazonyl chlorides afforded the target thiazoles in excellent isolated yields. By considering their elemental analyses and spectral findings, the structures of the new hybrids were clarified.     

2-Phenylindole derivatives as anticancer agents: synthesis and screening against murine melanoma,human lung and breast cancer cell lines

Indole derivatives have attractive anticancer properties and may be a future hope for better anticancer drug(s) of low toxicity and high potency. In this paper, syntheses of 2-phenylindole derivatives have been described via Fischer indole synthesis through a one-pot solvent-free method. The synthesized compounds were screened for anticancer potential in vitro against murine melanoma (B16F10), human lung cancer (A549), and human breast cancer (MDA-MB-231) cell lines. The results highlighted that 2-phenylindole derivatives are also promising anticancer agents in case of melanoma and lung cancer along with the breast cancer. Molecular docking analyses with possible targets for melanoma (NEDD4-1) and lung cancer (EGFR) were also performed to understand specific interactions of 2-phenylindole derivatives with the amino acid residues of the receptors.     

Concatenating Suzuki Arylation and Buchwald–Hartwig Amination by A Sequentially Pd-Catalyzed One-Pot Process—Consecutive Three-Component Synthesis of C,N-Diarylated Heterocycles

The concatenation of Suzuki coupling and Buchwald-Hartwig amination in a consecutive multicomponent reaction opens a concise, modular and efficient one-pot approach to diversely functionalized heterocycles, as exemplified for 3,10-diaryl 10H-phenothiazines, 3,9-diaryl 9H-carbazoles, and 1,5-diaryl 1H-indoles, in high yields starting from simple staring materials. Moreover, this one-pot reaction is a sequentially palladium-catalyzed process that does not require additional catalyst loading after the first coupling step.     

HyperMacs. Long Chain Branched Analogues of Hyperbranched Polymers Prepared by the Polycondensation of AB2 Macromonomers

We describe here a new strategy for the synthesis of polymers with highly branched architectures. The strategy involves the synthesis by anionic polymerization of well-defined AB₂ polystyrene macromonomers with molecular weights from 3,600 to 94,000 gmol⁻¹, which are then converted via a one-pot polycondensation reaction into high molecular weight, long-chain (hyper)branched architectures. Since the Hyperbranched structures are built up from condensation Macromonomers we have coined the term ‘HyperMac’ to describe these branched polymers. In this paper we report the synthesis of the HyperMacs, the optimal conditions for the polycondensation reaction and some preliminary characterization studies.     

HA/Ag纳米复合材料的制备与性能

采用一锅热熔胶法制备出多孔花状羟基磷灰石/银(HA/Ag)纳米复合材料。通过检测罗丹明B揭示了HA/Ag作为SERS活性底物的独特拉曼增强效应,其检测极限为10~(-8) mol·L~(-1)。在检测中,改变拉曼激光强度,取点位置等手段能有效提高检测的灵敏度。此外,所制备的多孔纳米复合材料HA/Ag作为对硝基苯酚(4-NP)还原为对氨基苯酚(4-AP)反应的催化剂,可以大大缩短反应时间40 min。     

One-pot synthesis of 5-fluoroalkyl-5-hydroxy-4-hydroxy-imino-1-isonicotinoyl-4,5-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrazoles and their tuberculostatic activity

5-Fluoroalkyl-5-hydroxy-4-hydroxyimino-1-isonicotinoyl-4,5-dihydro-1H-pyrazoles were synthesized via a one-pot procedure from polyfluoroalkyl-containing 1,3-diketones, sodium nitrite in acetic acid, and isoniazid. Acetylacetone gave rise to 3-hydroxyiminopentane-2,4-dione monoisonicotinoylhydrazone which underwent intramolecular cyclization to 5-hydroxy-4-hydroxyimino-1-isonicotinoyl-3,5-dimethyl-4,5-dihydro-1H-pyrazole on heating in ethanol. The synthesized compounds exhibited moderate tuberculostatic activity.     

One-Pot Synthesis of 1-Alkynylphosphonates

1-Alkynylphosphonates 3 are prepared in a one-pot procedure from diethyl phosphorochloridates 2 and alkynyllithiums 1, which are readily generated by the reaction of 1-alkynes with n-BuLi.     

2-Amino-4-aryl-6-(ω-carboxyalkyl)-5H-pyrrolo[3,4-d]pyrimidin-7-(6H)ones. Preparation via a one-pot synthesis of 1-(ω-carboxyalkyl)-4-carbethoxy-2,3-dioxopyrrolidines

1-(ω-Carboxyalkyl)-4-carboethoxy-2,3-dioxopyrrolidines were prepared by a one-pot synthesis from β-alanine or γ-aminobutyric acid, ethyl acrylate and diethyl oxalate. In a second one-pot process these products were hydrolyzed, decarboxylated and condensed with aromatic aldehydes under the influence of hydrochloric acid to yield 1-(ω-carboxyalkyl)-4-arylidene-2,3-dioxo-pyrolidines, which yielded 2-amino-4-aryl-6-(ω-carboxyalkyl)-5H-pyrrolo[3,4-d]pyrimidin-7-(6H)-ones upon treatment with guanidine. It was shown that 3,4-dihydro derivatives of certain 2-amino-4-aryl-5H-pyrrolo[3,4-d]pyrimidin-7-(6H)ones, formed initially in the guanidine reaction, readily undergo conversion to 5H-pyrrolo[3,4-d]pyrimidin-7-(6H)ones.     

Concise Total Synthesis of (−)-Erinapyrone B from D-(+)-Malic Acid

A convenient and facile enantioselective synthesis of (?)-erinapyrone B from commercially available D-(+)-malic acid has been achieved in seven steps. One of the key steps in this synthesis was the one-pot reaction of palladium(II)-mediated Wacker-type oxidative cyclization in the presence of a catalytic amount of p-toluenesulphonic acid (p-TsOH) which has been found to be effective for the preparation of enantiopure 2,3-dihydro-4H-pyran-4-one from the corresponding enantiopure β-hydroxyenone via enantio-enriched diketohydroxy intermediate.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Carbohydrate O-benzylation through trialkylsilane-mediated reductive etherification

Abstract

Trialkylsilane-mediated reductive etherification has been actively used in carbohydrate O-benzylation since it emerged decades ago. In this review, we first trace the origin, development, and possible reaction mechanism of trialkylsilane-mediated reductive etherification, then focus on its typical applications in carbohydrate synthesis including regioselective protection, one-pot combinatorial protection, and one-pot protection-glycosylation. At the end, we discuss its limitations and potentials in global benzylation.     

‘One-Pot’ Synthesis of Raumacline from Ajmaline

For the alkaloid raumacline ( 2 ), which is a biotransformation product of ajmaline ( 1 ) in Rauwolfia serpentina cell cultures, an efficient ‘one-pot’ synthesis was developed using a NaBH₄/riboflavin/light-mediated transformation of 1 into 2 with a total yield of 86%.