Xylan-type hemicelluloses supported terpyridine–palladium(II) complex as an efficient and recyclable catalyst for Suzuki–Miyaura reaction

Xylan-type hemicelluloses supported terpyridine–palladium(II) as a novel biomass-supported catalyst was synthesized and characterized in terms of morphology, composition, and thermal stability. The nano-Pd catalyst was further explored for Suzuki–Miyaura reaction between arylboronic acid and aryl halide under aerobic condition, with a yield up to 98 %. In particular, the catalyst exhibited both high catalytic activity and stability for Suzuki–Miyaura reaction. Furthermore, the catalyst could be easily recovered by simple filtration and reused at least six times without significant loss of its catalytic activity. This work provides a novel and effective supported catalyst, and broadens the applications of polysaccharides in green catalysis.     

Stereocontrolled transformation of nitrohexofuranoses into cyclopentylamines via 2-oxabicyclo[2.2.1]heptanes. Part 6: synthesis and incorporation into peptides of the first reported 2,3-dihydroxycyclopentanecarboxylic acid

Herein we report the intramolecular alkylation of nitronates of methyl-5-O-benzyl-3,6-deoxy-6-nitro-β-d-glucofuranoside and methyl-5-O-benzyl-3,6-deoxy-6-nitro-α-d-glucofuranoside into the corresponding 2-oxabicyclo[2.2.1]heptane derivatives. Similarly, methyl-3-O-benzyl-5-deoxy-5-nitromethyl-β-d-xylofuranoside and methyl-3-O-benzyl-5-deoxy-5-nitromethyl-α-d-xylofuranoside were cyclized to (1R,3R,4S,5R,7R)-7-benzyloxy-3-methoxy-5-nitro-2-oxabicyclo[2.2.1]heptane and (1R,3S,4S,5R,7R)-7-benzyloxy-3-methoxy-5-nitro-2-oxabicyclo[2.2.1]heptane, respectively. These 2-oxabicyclo[2.2.1]heptane derivatives were eventually transformed into enantiopure methyl (1S,2S,3R,4S,5R)-2-amino-2,3-dihydroxycyclopentanecarboxylate and this novel β-amino acid was incorporated into peptides.     

Asymmetric synthesis of cyclopropyl phosphonates using chiral terpenyl sulfonium and selenonium ylides

The asymmetric cyclopropanation of a vinylphosphonate using optically active sulfonium and selenonium ylides derived from (−)-menthol and (+)-limonene was developed. The ylides were generated in situ by the reaction of the corresponding sulfonium or selenonium salt in the presence of potassium carbonate or DBU as a base. The transfer of the CHPh and CHCO₂Et groups into the cyclopropane ring showed moderate diastereoselectivity and excellent enantioselectivity (up to 99:1) for the trans- and cis-products. The absolute configuration of phenyl cyclopropyl was assigned based on comparison to their tolyl analogues.     

Efficient One-Pot Synthesis of 3-Amino-7-azaindoles Under Microwave Irradiation

An efficient one-pot synthesis of 3-amino-7-azaindoles was developed, starting from ethyl (3-cyanopyridin-2-yl)carbamate and α -bromoketones by microwave-assisted Thorpe–Ziegler cyclization in the presence of a base. This method features excellent yields, short reaction time (10min), and high functional group compatibility.

[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.]     

Synthesis of oxindole-3-acetates through iron-catalyzed oxidative arylalkoxycarbonylation of activated alkenes

An iron-catalyzed alkoxycarbonylation/cyclization reaction of N-arylacrylamides with carbazates has been developed. This new alkene difunctionalization reaction provides an efficient and straightforward method to obtain various ester-containing oxindoles.     

Dopamine derivatives from the insect Polyrhachis dives as inhibitors of ROCK1/2 and stimulators of neural stem cell proliferation

Polyrhachis dives is consumed as an insect food in some regions of China. In this study, new dopamine derivatives, (+)-polyrhadopamine A (1a) and (−)-polyrhadopamine A (1b), (+)-polyrhadopamine B (2a) and (−)-polyrhadopamine B (2b), and polyrhadopamines C–E (3–5), were isolated from this species. The structures and stereochemistry of these substances were assigned by using spectroscopic and computational methods. Compounds 1a, 1b, 2a, and 2b are dimeric N-acetyldopamine derivatives, 3 is a dopamine analog containing an unusual sulfone group, and 4 and 5 possess a rare benzo[d]thiazole moiety. The functions of these substances as ROCK1/2 inhibitors, neural stem cell (NSCs) proliferation stimulators, immunosuppressive, and anti-inflammatory agents were determined.     

Novel cytotoxic nine-membered macrocyclic polysulfur cembranoid lactones from the soft coral Sinularia sp.

One novel nine-membered macrocyclic polysulfur cembranoid lactone, sinulariaoid A (1); three new multioxygenated cembranoids, sinulariaoid B (2), sinulariaoid C (3), sinulariaoid D (4); and four known cembranoids, capilloloid (5), dihydrosinularin (6), sinularin (7), and dihydrosinuflexolide (8) were isolated from the soft coral Sinularia sp. collected off of Sanya Bay in the South China Sea. Their stereochemical structures were determined on the basis of extensive spectroscopic methods, including single crystal X-ray diffraction analysis. Sinulariaoid A (1) is the first reported nine-membered macrocyclic polysulfur cembranoid from soft coral. The cytotoxic activities of compounds 1–8 were determined in four human cancer cell lines (HepG2, HepG2/ADM, MCF-7, and MCF-7/ADM). Of these, sinulariaoid A (1) exhibited the most potent anticancer activity in vitro, and its cytotoxicity in HepG2/ADM was more potent than in the other three cell lines. Furthermore, it was found that sinulariaoid A (1) induced apoptosis, and its selective toxicity toward HepG2/ADM cells was not related to P-glycoproteins.     

Chemoenzymatic synthesis of β-carboline derivatives using McbA,a new ATP-dependent amide synthetase

McbA was characterized in vitro as a novel amide synthetase in the marinacarbolines A–D biosynthetic pathway, catalyzing amide bond formation between 1-acetyl-3-carboxy-β-carboline (1a) and substituted-β-phenethylamines (1b, 2b, 3b) and tryptamine (4b) in an ATP-dependent manner. Enzyme kinetic analyses highlight β-phenethylamine as the most suitable amine donor. McbA showed broad substrate compatibility with substituted amines; 10 new β-carboline analogues were chemoenzymatically generated.     

A spectral similarity measure using Bayesian statistics

A spectral similarity measure was developed that can differentiate subtle differences between two spectra. The spectra are digitalized into a vector. The difference between the two spectra is defined by a difference vector, which is one spectrum minus the other. The spectral similarity measure is transformed into a hypothesis test of the similarities and differences between the two spectra. The scalar mean of the difference vector is used as the statistical variable for the hypothesis test. A threshold for the hypothesis that the spectra are different was proposed. The Bayesian prior odds ratio was estimated from multiple spectra of the same sample. The posterior odds ratio was used to quantity the spectral similarity measure of the two spectra. Diffuse reflectance near-infrared spectra of tobacco samples of two formulations were used to demonstrate this method. The results show that this new method can detect subtle differences between the spectra.     

Application of solid-phase microextraction for the determination of organophosphorus pesticides in textiles by gas chromatography with mass spectrometry

A method based on solid-phase microextraction (SPME) and gas chromatography with mass spectrometry (GC/MS) for the determination of 18 organophosphorus pesticides (OPPs) in textiles is described. Commercially available SPME fibers, 100 μm PDMS and 85 μm PA, were compared and 85 μm PA exhibited better performance to the OPPs. Various parameters affecting SPME, including extraction and desorption time, extraction temperature, salinity and pH, were studied. The optimized conditions were: 35 min extraction at 25 °C, 5% NaSO₄ content, pH 7.0, and 3.5 min desorption in GC injector port at 250 °C. The linear ranges of the SPME-GC/MS method were 0.1-500 μg L⁻¹ for most of the OPPs. The limits of detection (LODs) ranged from 0.01 μg L⁻¹ (for bromophos-ethyl) to 55 μg L⁻¹ (for azinphos-methyl) and the RSDs were between 0.66% and 9.22%. The optimized method was then used to analyze 18 OPPs in textile sample, and the determined recoveries were ranged from 76.7% to 126.8%. Moreover, the distribution coefficients of the OPPs between 85 μm PA fiber and simulative sweat solution (K_pa/s) were determined. The determined K_pa/s of the OPPs correlated well with their octanol-water partition coefficients (r = 0.764 and 0.678) and water solubility (r = −0.892 and −0.863).