Total Synthesis of (-)-Tetrahydrolipstatin by the Tandem Mukaiyama-aldol Lactonization

（-）-Tetrahydrolipstatin 1 was synthesized in three steps and 33.8% overall yield from aldehyde 6 by tandem Mukaiyama-aldol lactonization, which offered a concise, efficient and highly diastereoselective route to this antiobesity drug. We also presented a resolution method for preparation of the crucial intermediate, β- （t-butyldimethylsilyloxy）tetradecanal.

Preparation of a ε-caprolactonic diterpenoid derivate by unexpected oxidative cleavage/lactonization of 2-oxoaustroeupatol

From aerial parts of Austroeupatorium inulifolium was isolated the ent-nor-furano triol labdane austroeupatol 1.The compound 1 was treated with IBX showing an unexpected selectivity at the potentially oxidizable sites of the sub-strate yielding the 2-oxoaustroeupatol(2)and 2,19-dioxoaustroeupatol(3).The treatment of 2 with sodium periodate yields a heterocyclic derivative(ε-caprolactone derivate 4)formed by oxidative cleavage and unexpected intramo-lecular attack of the hydroxymethylene(C-19)oxygen to the ketonic carbon(C-2).A plausible mechanistic pathway for the obtention of compound 4 is proposed.

Lactonization of 5-Phenylfuran-4-arylcarbinol-3-carboxylic Acids under the Catalysis of Boron Trifluoridc Etherate

?-Phenyl－4－aroylfuran－3－carboxylic acids were reduced in aqueous alkaline solutions ofNaBH4 to afford hydroxy acids in excellent yields． Under the catalysis of boron trifluoride etherate，the hydroxy acids were converted to lactones smoothly．

Difluoroalkylation/Lactonization of Alkenes with BrCF_(2)CO_(2)K via Photoredox Catalysis:Access toα,α-Difluoro-γ-lactones

Due to its unique electronic properties,the difluoromethylene group(CF2)has served as a valuable unity in the design of biologically active molecules.Sinceγ-lactones display a broad range of biological properties,α,α-difluoro-γ-lactones may exhibit unexpected biological activities,and thus their synthesis has received increasing attention.Traditional synthetic methods suffer from tedious multi-step processes,and very few effective methods have been reported recently.Herein,we describe the difunctionalization of alkenes with BrCF_(2)CO_(2)K under photoredox catalysis with the use of a boron-Lewis acid for the access toα,α-difluoro-γ-lactones.In this transformation,the alkene substrates and the used reagents,including BrCF_(2)CO_(2)K and the boron-Lewis acid,PhB(OH)2 or BF3·THF,are cheap and widely available.High efficiency and atom economy may make this protocol attractive.

Lactonization of C（sp2）-H Bonds in Enamides with CO2

Herein, we report a novel synthesis of 1,3-oxazin-6-ones from enamides with CO2 through C--H carboxylation and one-pot cyclization. This transition-metal-free and redox-neutral process features broad substrate scope, good functional group tolerance and facile product derivatization. The nucleophilic attack to CO2 from the electron-rich alkene is demonstrated for this reaction.

Britanin–a beacon of hope against gastrointestinal tumors?

Britanin is a bioactive sesquiterpene lactone known for its potent anti-inflammatory and anti-oxidant properties.It also exhibits significant anti-tumor activity,suppressing tumor growth in vitro and in vivo.The current body of research on Britanin includes thirty papers predominantly related to neoplasms,the majority of which are gastrointestinal tumors that have not been summarized before.To drive academic debate,the present paper reviews the available research on Britanin in gastrointestinal tumors.It also outlines novel research directions using data not directly concerned with the digestive system,but which could be adopted in future gastrointestinal research.Britanin was found to counteract liver,colorectal,pancreatic,and gastric tumors,by regulating proliferation,apoptosis,autophagy,immune response,migration,and angiogenesis.As confirmed in pancreatic,gastric,and liver cancer,its most commonly noted molecular effects include nuclear factor kappa B and B-cell lymphoma 2 downregulation,as well as Bcl-2-associated X protein upregulation.Moreover,it has been found to induce the Akt kinase and Forkhead box O1 axis,activate the AMP-activated protein kinase pathway,elevate interleukin-2 and peroxisome proliferator-activated receptor-γlevels,reduce interleukin-10,as well as downregulate matrix metalloproteinase-9,Twist family bHLH transcription factor 1,and cyclooxygenase-2.It also inhibits Myc–HIF1αinteraction and programmed death ligand 1 transcription by interrupting the Ras/RAF/MEK/ERK pathway and mTOR/P70S6K/4EBP1 signaling.Future research should aim to unravel the link between Britanin and acetylcholinesterase,mast cells,osteolysis,and ischemia,as compelling data have been provided by studies outside the gastrointestinal context.Since the cytotoxicity of Britanin on noncancerous cells is significantly lower than that on tumor cells,while still being effective against the latter,further in-depth studies with the use of animal models are merited.The compound exhibits pleiotropic biological activity and offers considerable promise as an anti-cancer agent,which may address the current paucity of treatment options and high mortality rate among patients with gastrointestinal tumors.

Oxidative lactonization of C(sp^(3))–H bond in methyl aromatic alcohols enabled by proton-coupled electron transfer

Direct functionalization of inert C(sp^(3))–H bonds in pharmaceutically significant compounds is very important in modern synthetic organic chemistry.In this article,we disclose a practical and efficient method for the oxidative lactonization of benzylic C(sp^(3))–H bonds enabled by the synergistic interactions of organic dye-type rose bengal,n-Bu_(4)N∙Br,O_(2) and Na_(2)HPO_(4) under visible light irradiation.This reaction does not require transition metal catalysts or strong oxidants.A range of structurally diverse phthalides has been synthesized with excellent selectivity and high functional group compatibility.The late-stage application of this reaction to the preparation of structurally complex phthalides demonstrates its synthetic utility.

A Preliminary Study of Cell Membrane Mediated Immobilization of a Recombinant Acyl-homoserine Lactonase AidH

The aim of this work was to inhibit biofilm formation by taking advantages of bacterial surface display technology in combination with cell membrane chromatography.A recombinant protein INPAidH was constructed by fusing a quorum signal hydrolase AidH to the C-terminus of the ice nucleation protein(INP).Expression of INP-AidH was achieved on E.coli cell surface at an expression level of 30%of total membrane proteins.Activity of INP-AidH on cell membranes was confirmed in degrading the quorum signal C6-HSL as well as inhibiting bacterial biofilm.Immobilization of INP-AidH anchored cell membranes on silica gel particles was facilitated by taking advantages of cell membrane chromatography.The functionalized silica gel particles also exhibit activities in degrading C6-HSL and inhibiting bacterial biofilm.This article presents a new approach to prevent biofilm formation of silica-based materials.

Histone Deacetylation Modifier Induced One New Resorcylic Acid Lactone 7′(Z)-zeaenol from the Zoanthid-Derived Fungus Cochliobolus lunatus

Chemical epigenetic manipulation was applied to the zoanthid-derived fungus Cochliobolus lunatus(TA26-46)with a histone deacetylation modifier(100μmol L^(−1) nicotinamide),resulting in the isolation of a new 14-membered resorcylic acid lactone named 7′(Z)-zeaenol(1),together with six known analogues(2−7)from the treated broth.The planar structure of 1 was determined by comprehensive NMR spectroscopy and HRESIMS data.The absolute configuration of 1 was elucidated by ECD spectrum,^(13)C NMR shift calculations,and on the basis of biogenetic considerations.Compound 5 exhibited cytotoxic activity against the human tumor cell lines A549,HCT-116,HT-29,Hela,MCF-7,and K562 with the IC_(50) values ranging from 2.54 to 7.44μmolL^(−1).

Degradation of N-Acyl Homoserine Lactone Quorum Sensing Signals by Bacillus thuringiensis AHL Lactonase

Bacterial cells rely on signaling molecules to communicate with others from the same species and induce certain genes in a process known as quorum sensing (QS). A common molecule is N-acyl homoserine lactone (AHL) which is responsible for the expression of virulence and other factors that allow the organisms to compete in a given environment. On the other hand, other bacteria produce certain enzymes such as AHL-lactonase that break down AHL molecules and prevent gene expression of these factors. The aim of this work was to examine the level of degradation of AHL molecules by AHL-lactonase in 62 Bacillus thuringiensis (Bt) strains isolated from Middle Tennessee, Mississippi, and Alabama. N-hexanoyl-homoserine lactone (C6-HSL) and N-3-oxo-hexanoyl homoserine lactone (3-oxo-C6-HSL), which cause Chromobacterium violaceum (CV026) to produce a purple pigment were tested at different concentrations to view the Bt lactonase activity. In addition, PCR was used to test for the presence of the lactonase gene. The results showed that among the 62 Bt strains, there were 58 that possessed the AHL-lactonase (aiiA) gene and 48 strains were able to degrade C6-HSL. At high concentrations of AHL, only 13 strains were able to completely degrade C6-HSL. In addition, degradation of 3-oxo-C6-HSL was weak compared to C6-HSL. The results also revealed that AHL lactonase was thermostable, and it was concluded that the level of degradation varies in Bt strains. Only 13 of the strains studied have potent inhibitory activity against C6-HSL, which may be good to be used in field applications to control agricultural pest.

Stereoselective Functionalization at C-2 and C-3 of the Gibberellin via an Intramolecular Free Radical Cyclization Approach

Stereoselective functionalization at C-2 and C-3 of the gibberellin skeleton was achieved via an intramolecular free radical cyclization approach using a tethered C-19 halomethyl ester as the radical precursor.

生物降解织物与农业

论述现今在业上使用最多的塑膜对农业环境的影响;开发生物降解织物的现实意义;简介几种生物降解纤维(甲壳素纤维、Lyocell纤维,Lacton纤维等)及织物的制造方法;并叙述了生物降解织物在农业上的主要功能及应用。

Synthesis of Z and E-(2',5'-dimethoxyphenyl)-methylene-butyrolactones

A pair of Z and E isomers of cyclization of γ-ketoacid 7, which was prepared in six steps from 2,5-dimethoxyphenyl acetic acid 1, gave a pair of Z(20%) and E (4%) isomers of (2,5-dimethoxyphenyl)-methylene-butyrolactones

Synthetic Studies of Naphtho[2,3-b]furan Moiety Present in Diverse Bioactive Natural Products

The preparation of several functionalized furan derivatives and attempts to transform them into a derivative containing 6H-furo[3,4-b]furanone skeleton towards the construction of naphtho[2,3-b] furan are described. Attempted Pummerer reaction of a furan sulfoxide derivative produced four interesting furan derivatives. Base promoted annulation between methyl 2-(phenylsulfinylmethyl)-3-furoate and 2-cyclohexenone proceeded to give dihydro naphtho[2,3-b]furanone derivative in a regiospecific manner.

Sesquiterpene Lactones from Elephantopus scaber

A new germacranolide sesquiterpene lactone, isoscabertopin, was isolated from Elephantopus scaber together with the known scabertopin. Their structures were determined by spectroscopic methods.

A new cassane diterpenoid lactone from the seed of Caesalpinia minax

A new cassane diterpenoid lactone was isolated from the seed of Caesalpinia minax. On the basis of spectral evidences, its structure was established as 12α-methoxyl, 5α, 14β-dihydroxy-1α, 6α, 7β-triacetoxycass-13（15）-en-16, 12-olide.

Three Novel Eremophilanolides from Ligularia virgaurea spp.oligocephala

From the alcoholic extract of the whole plant of Ligularia virgaurea spp. oligocephala,three novel eremophilane sesquiterpene lactones, 6α, 10α-dihydroxy-1-oxoeremophila- 7(11),8(9)-dien-8, 12-olide, 6β, 10α-dihydroxy-1-oxoeremophila-7 (11), 8 (9)-dien-8, 12-olide and10α-diydroxy-1-oxoeremophila-7(11), 8 (9)-dien-8, 12 olide were isolated. Their structure s wereelucidated by various, spectroscopic methods including intensive 2D NMR techniques (COSY,HMQC, HMBC and ~1H-~1H NOESY) and HR-MS.

A New Sesquiterpene Lactone from Ainsliaea bonatii

A new sesquiterpene lactone, Ainsliaolide A, was isolated from Ainsliaea bonatii. Thestructure was determined on the basis of spectral data.