Efficient palladium-catalyzed N-arylation of a sulfoximine with aryl chlorides

The efficient N-arylation of a sulfoximine with aryl chlorides was developed by using Pd(2)(dba)(3) as a catalyst and various ligands. The reactions using RuPhos as a ligand afforded the coupled products in fair to excellent yields.     

Metabolites from the xylariaceous fungus PSU-A80

One hypoxylonol, xylarenol (1), one hexadienoic acid, xylarenoic acid (2), and one tetralone, xylarenone (3), were isolated from the xylariaceous fungus PSU-A80 together with ten known compounds. The structures were established by analysis of spectroscopic data. 8-Methoxy-1-naphthol, one of the known metabolites, displayed good radical scavenging potency with an IC(50) value of 30 microg/ml.     

Synthesis and Biological Activities of Azalamellarins

The synthesis of azalamellarins, a new series of lactam analogues of biologically active lamellarins, was achieved using Cu^I‐mediated and microwave‐assisted C? N_amide bond formation. Seventeen azalamellarins, including N‐allylazalamellarins and N‐propylazalamellarins χ‐D, L ‐N, and J‐dehydro J, were synthesized and evaluated for their cytotoxicity against the cancer cell lines HuCCA‐1, A‐549, HepG2, and MOLT‐3. The results showed that certain azalamellarins exhibited good activities in the micromolar IC₅₀ value range (IC₅₀=the drug concentration that causes 50 % of cell‐growth inhibition after 72 h of continuous exposure to the test molecule), comparable to their parent lamellarin analogue.     

Xanthones from a lignicolous freshwater fungus (BCC 28210)

Abstract

Four xanthones (1?4) and a known compound, mansonone D (5), were isolated from the lignicolous freshwater fungus BCC 28210 (family, Chaetosphaeriaceae). The structures of these compounds were elucidated by extensive spectroscopic analysis. Among the isolated metabolites, compound 2 and the known mansonone D (5) displayed antimalarial activity against Plasmodium falciparum K1 with IC₅₀ values of 7.75 and 0.55?μg/mL, respectively. Compound 4 displayed antibacterial activity against Bacillus cereus with an MIC value of 6.25?μg/mL.     

Highly diastereoselective synthesis of beta-carboxy-gamma-lactams and their ethyl esters via Sc(OTf)(3)-catalyzed imino Mukaiyama-aldol type reaction of 2,5-bis(trimethylsilyloxy)furan with imines

Functionalized gamma-lactams are found to be crucial intermediates in the synthesis of biologically important natural products. We herein described a highly diastereoselective synthesis of beta-carboxy-gamma-lactams and their ethyl ester derivatives, in high yields with high diastereomeric ratio, via the Mukaiyama-aldol type reaction of 2,5-bis(trimethysilyloxy)furan with imines, employing Sc(OTf)(3) as a catalyst.     

Cytotoxic tropolones from the fungus Nemania sp. BCC 30850

Twelve new compounds, including nine tropolones, nemanolones A?I (1–9), three 7-isochromenones, nemanecins A?C (10–12), and a new naturally isolated 4-isochromanone (13), along with two known compounds, 7,8-dihydroxy-3-methyl isochroman-4-one (XJP), and chaetoquadrin F, were isolated from culture broth of the fungus Nemania sp. BCC 30850. Structures of these compounds were elucidated by NMR and MS spectroscopic analyses. Nemanolones exhibited cytotoxic activities and two of them, compounds 1 and 2, also showed antibacterial activity against Bacillus cereus and antifungal activity against Candida albicans.     

Acrylamide/2-acrylamido-2-methylpropane sulfonic acid and associated sodium salt superabsorbent copolymer nanocomposites with mica as fire retardants

Acrylamide (AM) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS-H⁺) or its sodium salt (AMPS-Na⁺) were copolymerised by free-radical crosslinking polymerization to obtain poly(AM-co-AMPS-H⁺) and poly(AM-co-AMPS-Na⁺) superabsorbent polymers (SAPs). A maximum water absorbency in deionised water of 1200 g g⁻¹ was achieved for poly(AM-co-AMPS-Na⁺) at a 85% mol of AMPS-Na⁺. The inclusion of mica at 5-30% (w w⁻¹) into the preparation of poly(AM-co-AMPS-Na⁺) SAP leads to an intercalated structure, as detected by XRD and TEM analyses. Poly(AM-co-AMPS-Na⁺)/30% (w w⁻¹) mica SAP nanocomposite showed a tap water absorbency of 593 g g⁻¹ with a better thermal stability, compared to the pure SAP. Cone calorimetric analyses revealed that the wood specimens coated with the prepared poly(AM-co-AMPS-Na⁺) SAP or its 30% (w w⁻¹) mica nanocomposite provided excellent protection in delaying the ignition time after exposure to an open flame when compared to that observed with the uncoated specimen. The maximum reduction in the peak heat release rate and the greatest extension of time at peak heat release rate were observed with the nanocomposite-coated surface, but the total heat release rate was increased. The delayed burning mechanism is brought by the intercalating structure of mica in the SAP nanocomposites, which provided a better shielding effect against external heat sources, and the capability of the SAP nanocomposite in holding a large amount of water.     

Isoselective Lactide Ring Opening Polymerisation using [2]Rotaxane Catalysts

Polylactide (PLA) is a fully biodegradable and recyclable plastic, produced from a bio‐derived monomer: it is a circular economy plastic. Its properties depend upon its stereochemistry and isotactic PLA shows superior thermal‐mechanical performances. Here, a new means to control tacticity by exploiting rotaxane conformational dynamism is described. Dynamic achiral [2]rotaxanes can show high isoselectivity (P_i=0.8, 298 K) without requiring any chiral additives and enchain by a chain end control mechanism. The organocatalytic dynamic stereoselectivity is likely applicable to other small‐molecule and polymerization catalyses.     

Further observations on water oxidation catalyzed by mononuclear Ru(II) complexes

A family of 28 mononuclear Ru(II) complexes have been prepared and characterized by (1)H NMR, electronic absorption, and cyclic voltammetry. These complexes are studied as catalysts for water oxidation. All the catalysts possess one tridentate ligand, closely related to 2,2';6,2'-terpyridine (tpy) and may be divided into two basic types. In the type-1 catalyst, the three remaining coordination sites are occupied by a bidentate closely related to 2,2'-bipyridine (bpy) and a monodentate halogen (Br, Cl, or I) or water molecule. In the type-2 catalyst, the three remaining coordination sites are occupied by two axial 4-picoline molecules and an equatorial halogen or water. In general the type-2 catalysts are more reactive than the type-1. The type-2 iodo-catalyst shows first-order behavior and, unlike the bromo- and chloro-catalysts, does not require water-halogen exchange to show good activity. The importance of steric strain and hindrance around the metal center is examined. The introduction of three t-butyl groups at the 4, 4', and 4' positions of tpy sometimes improves catalyst activity, but the effect does not appear to be additive.