Four new indole alkaloids from Plantago asiatica

Four new indole alkaloids,plasiaticines A-D(1-4),together with two known ones,were isolated from the seeds of Plantago asiatica.The structures of the new compounds were elucidated on the basis of comprehensive analysis of spectroscopic data.All compounds were tested for their cytotoxic activity,and all compounds except 4 were tested for their acetylcholinesterase(AChE)inhibitory activities.

Four new lignans from the leaves and stems of Schisandra propinqua var.sinensis

Four new tetrahydrofuran lignans,schpropinrins A-D(1-4),together with five known ones,were isolated from the leaves and stems of Schisandra propinqua var.sinensis.Their structures,including absolute configurations,were characterized by means of spectroscopic analysis and ECD calculation.Compounds 1-4 featured a ketal or hemiketal substructure at C-7 and all of the isolates were tested for their anti-HIV integrase activity.

Two new neolignans from Manglietia insignis

Two new neolignans,manneoinsigins A(1)and B(2),together with four known lignans,were isolated from the leaves and stems of Manglietia insignis.The new compounds were established on the basis of extensive spectroscopic analyses.All compounds except 2 were tested for their cytotoxic activity.Compound 3 showed weak cytotoxic activity against the HL-60 human tumor cell line with the IC50 value of 23.5μM.

C_(Ar)-Br bond cleavage via cooperative EnT/NHC catalysis: mild access to indolines

The cooperative visible-light mediated and NHC-catalyzed dearomative arylation-acylation of N-(2-bromobenzoyl)indoles with aldehydes was developed, affording the corresponding highly functionalized polycyclic indolines in moderate to good yields with exclusive diastereoselectivities. Mechanism investigations support the activation of CAr-Br bond via visible-light mediated energy transfer(EnT) and the following single-electron-transfer(SET) with Breslow intermediate under NHC catalysis to give key aryl radical and ketyl radical. This protocol demonstrates the cleavage of CAr-Br bond under mild cooperative EnT/NHC catalysis.

Biomimetic asymmetric catalysis

Enzymes are the core for biological transformations in nature.Their structures and functions have drawn enormous attention from biologists as well as chemists since last century.The large demand of bioactive molecules and the pursuit of efficiency and greenness of synthesis have spurred the rapid development of biomimetic chemistry in the past several decades.Biomimetic asymmetric catalysis,mimicking the structures and functions of enzymes,has been recognized as one of the most promising synthetic strategies for the synthesis of valuable chiral compounds.This review summarizes the evolution of asymmetric catalysis inspired by aldolases,vitamin B_(1)/B_(6)-dependent enzymes,NAD(P)H,flavin,hydrogenases,heme oxygenases,nonheme oxygenases,and dinuclear/multinuclear metalloenzymes in aspects of biomimetic design,catalyst development and related catalytic transformations.Those well-established synthetic approaches originating from biological reactions have demonstrated the unique prowess of biomimetic asymmetric catalysis in bridging the gap between bio-catalysis and chemical synthesis.

Intramolecular α-Oxygenation of Amines via N-Heterocyclic Carbene-Catalyzed Domino Reaction of Aryl Aldehyde: Experiment and DFT Calculation

We have developed an N-heterocyclic carbene(NHC)-catalyzed domino reaction with aryl alde-hyde through a simple acyl azolium intermediate using phenyliodine(III)diacetate(PIDA)as an oxi-dant.Controlled experiments and density functional theory calculations supported a domino two-stage mechanism from aldehyde/amine to anα-oxygen-ation product,including NHC-catalyzed oxidation of the aldehyde to carboxylic acid via acyl azolium intermediate,and further,an addition of carboxyl-ate to iminium intermediate.Our study reveals a new model for the oxidation of Breslow intermedi-ate via electrophilic attack of the hydroxyl group by PIDA.