Acetal and ketal deprotection using montmorillonite K10: The first synthesis of syn-4,8-dioxatricyclo[5.1.0.03,5]-2,6-octanedione

Supramolecular nanomedicine for selective cancer therapy via sequential responsiveness to reactive oxygen species and glutathione

Cancer cells are generally immersed in an oxidative stress environment with a high intracellular reduction level. Thus, nanocarriers with sequential responsiveness to oxidative and reductive species, matching the traits of high oxidation in the tumor tissue microenvironment and high reduction potential inside cancer cells, are highly desired for specific cancer therapy. Herein, we report a supramolecular nanomedicine comprised of a reduction-responsive nanoparticle (NP) core whose surface was modified by an oxidation-responsive polyethylene glycol (PEG) derivative via strong host-guest interactions. In this delicate design, the PEGylation of NPs not only reduced their immunogenicity and extended systemic circulation, but also enabled oxidation-responsive de-PEGylation in the tumor tissues and subsequent intracellular payload release in response to glutathione (GSH) inside tumor cells. As a proof of concept, this supramolecular nanomedicine exhibited specific chemotherapeutic effects against cancer in vitro and in vivo with a decent safety profile.

Benzyltriphenylphosphonium Peroxodisulfate: A Mild and Inexpensive Reagent for Selective Oxidative Deprotection of Trimethylsilyl and Tetrahydropyranyl Ethers, Ethylene Acetals and Ketals under Non-Aqueous and Aprotic Conditions

Benzyltriphenylphosphonium peroxodisulfate has been found to be an effective reagent for the oxidative deprotection of trimethylsilyl (TMS) and tetrahydropyranyl (THP) ethers, ethylene acetals and ketals to their corresponding carbonyl compounds in excellent yields. Selective oxidative deprotection of TMS ethers in the presence of THP ethers and ethylene acetals (ketals) makes this method a useful and practical procedure in organic synthesis.

Bifunctional Mesoporous Carbon Nitride: Highly Efficient Enzyme-like Catalyst for One-pot Deacetalization-Knoevenagel Reaction

Recently, mesoporous carbon nitride (MCN) has aroused extensive interest for its potential applications in organocatalysis, photo- and electrochemistry and CO2 capture. However, further surface functionalization of MCN for advanced nanomaterials and catalysis still remains very challenging. Here we show that acidic carboxyl groups can be smoothly introduced onto the surface of well-ordered MCN without annihilation between the introduced acid groups and MCN's inherent basic groups through a facile UV light oxidation method. The functionalization generates a novel bifunctional nanocatalyst which offers an enzyme-like catalytic performance in the one-pot deacetalization-Knoevenagel reaction of benzaldehyde dimethylacetal and malononitrile with 100% conversion and more than 99% selectivity due to the cooperative catalysis between the acid and base groups separated on the surface of the catalyst. The results provide a general method to create multifunctional nanomaterials and open new opportunities for the development of high efficient catalyst for green organic synthesis.

Synthesis and antitumor activity of lapathoside D and its analogs

Phenylpropanoid sucrose esters are important class of plant-derived natural products and have greater potential to be leads for new drugs because of their structural diversity and broad-array of pharmacological and biological activities. Regio- and chemo-selective acylation of 2,1':4,6-O-di-isopropylidene sucrose 4 with cinnamoyl chloride 5 and p-acetoxycinnamoyl chloride 6 afforded mono-, di-, tri- and tetra- variant PSEs in moderate yields. The first total synthesis of di-substituted PSE, lapathoside D 1' has been achieved successfully in short and simple synthetic steps from sucrose 3 as an inexpensive starting material. Lapathoside D 1 and a set of selected synthesized PSEs were tested for in vitro cytotoxicity against human cervical epithelioid carcinoma (HeLa) cell lines. Most of the compounds exhibited significant antitumor activity with their IC(50) values ranging from 0.05 to 7.63 μM. The primary screening results indicated that PSEs might be valuable source for new potent anticancer drug candidates.

Zeolites and other silicon-based promoters in carbohydrate chemistry

Silicon-based materials, namely zeolites, clays, and silica gel have been widely used in organic synthesis, allowing mild reaction conditions and environmentally friendly methodologies. These heterogeneous catalysts are easy to handle, possess nontoxic and noncorrosive character and offer the possibility of recovery and reuse, thus contributing to clean and sustainable organic transformations. Moreover, they present shape-selective properties and provide stereo- and regiocontrol in chemical reactions. Herein, we survey the most significant applications of silicon-based materials as catalysts in carbohydrate chemistry, to mediate important transformations such as glycosylation, sugar protection and deprotection, and hydrolysis and dehydration. Emphasis is placed on their promising synthetic potential in comparison with conventional catalysts.

Convenient and efficient syntheses of 4-hydroxy-2(E)-nonenal and 4-oxo-2(E)-nonenal

Lipid peroxidation products 4-hydroxy-2(E)-nonenal (HNE) and 4-oxo-2(E)-nonenal (ONE) were conveniently synthesized using Wittig and Horner-Wardsworth-Emmons (HWE) reaction. Wittig or HWE reaction between an easily prepared phosphorane or phosphonate with glyoxal dimethyl acetal gave a protected 4-oxo-2(E)-nonenal. Hydrolysis gave 4-oxo-2(E)-nonenal, whereas reduction followed by hydrolysis gave 4-hydroxy-2(E)-nonenal.

Total Synthesis and Stereochemical Assignment of the Spiroisoxazoline Natural Product (+)-Calafianin1

Synthesis of the spiroisoxazoline natural product (+)-calafianin is reported using asymmetric nucleophilic epoxidation and nitrile oxide cycloaddition as key steps. Synthesis and spectral analysis of all calafianin stereoisomers led to unambiguous assignment of relative and absolute stereochemistry.

Synthesis of Epoxyquinol A and Related Molecules: Probing Chemical Reactivity of Epoxyquinol Dimers and 2H-Pyran Precursors

Total syntheses of the epoxyquinoid dimers, epoxyquinols A, B, and epoxytwinol A (RKB-3564 D), have been accomplished employing [4 + 2] and [4 + 4] dimerization of 2H-pyran epoxyquinol monomers. Modifications of 2H-pyran precursors have been explored, including alteration of epoxy alcohol and diene stereochemistry. A stable 2H-pyran prepared by alteration of the epoxyquinol 2H-pyran nucleus was evaluated as a diene in Diels-Alder cycloaddition with reactive dienophiles. Extensive studies for improving the [4 + 4] dimerization of selectively protected 2H-pyran monomers to afford the novel epoxyquinoid dimer epoxytwinol A were carried out, and valuable insight regarding competitive [4 + 2] and [4 + 4] dimerization processes has been obtained. In addition, chemical reactivities and structural modifications of epoxyquinol dimers have been evaluated, including [2 + 2] photocycloaddition and [3,3] sigmatropic rearrangement, indicating the possibility for production of novel structural diversity from dimeric epoxyquinoid natural product frameworks.

Synthesis of the Eastern Portion of Ajudazol A Based on Stille Coupling and Double Acetylene Carbocupration

[structure: see text] A strategy for the synthesis of ajudazol A, an unusual, pharmacologically active metabolite from myxobacteria, based on the Stille cross-coupling of a 2-stannyl-oxazole with a vinyl iodide unit is described; the vinyl halide unit containing a (Z,Z)-diene was prepared in one pot by the double acetylene carbocupration of a functionalized alkyl cuprate followed by trapping with 2,3-dibromopropene.

Montmorillonite K10 clay: an efficient catalyst for the one-pot stereoselective synthesis of beta-acetamido ketones

An efficient one-pot three-component coupling process for the synthesis of beta-acetamido ketones catalyzed by montmorillonite K10 clay is described. The reaction is highly stereoselective and the catalyst can be recycled.

Highly efficient deprotection of aromatic acetals under neutral conditions using beta-cyclodextrin in water

Aromatic acetals have been deprotected to the corresponding aldehydes under biomimetic conditions for the first time using beta-cyclodextrin in water under neutral conditions, thereby overcoming many of the drawbacks associated with earlier methodologies. This method, apart from being simple with regard to recycling of the catalyst, also has the potential for industrial applications.

Deprotection of Acetals and Ketals by Silica Sulfuric Acid and Wet SiO2

Neat chlorosulfonic acid reacts with silica gel to give silica sulfuric acid in which sulfuric acid is immobilized on the surface of silica gel via covalent bonds. A combination of silica sulfuric acid and wet SiO₂ was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under thermal conditions.

Asymmetric total synthesis of (+)-fostriecin

[structure: see text] The title compound, a potent protein phosphatase inhibitor and anticancer agent, was prepared by an efficient, multiconvergent asymmetric synthesis. Key transformations include a ring forming olefin metathesis leading to the alpha,beta-unsaturated lactone and creation of the triene moiety via Suzuki cross-coupling.

Synthesis of a Glycolipidic Amphiphilic Nitrone as a New Spin Trap

The synthesis of a new amphiphilic nitrone, A, derived from a digalactosyl tris(hydroxymethyl)aminomethane bearing a perfluorocarbon chain is described. A exhibited a surfactant behavior (cmc = 1.6 x 10(-)(5) mol/L), and the specific recognition of the galactosyl moiety grafted on A by the KbCWL1 membrane lectin was established. Preliminary experiments showed that A was able to trap free radicals in aqueous media, the shape of the observed ESR spectra being strongly dependent upon the nature of the trapped free radical.