NATURAL PRODUCTS SYNTHESIS BY RETRO-DIELS-ALDER REACTION Ⅱ~1 ASYMMETRIC SYNTHESIS OF (+) AND (-) 5-OXO-ENDO-TRICYCLO [5.2.1.0.^(2, 6)] DECA-3, 8-DIENE 1 BY ENZYME-CATALYZED REACTION

Asymmetric syntheses of both enantiomerically pure (+) and (-) 5-oxo-endo-tricyclo [5.2.1.0.^(2,6)] deca-3, 8-diene 1 was described. The key step is the use of enzyme-catalyzed hydrolysis of meso-diacetate 5.

NATURAL PRODUCTS SYNTHESIS BY RETRO-DIELS-ALDER REACTION Ⅷ~1 A CONCISE STEREOSPECIFIC FORMAL SYNTHESIS OF TETRAHYDROCHLOROVULONE

A potent antineoplastic tetrahydrochlorovulone 3 was synthesized with retro-Diels Alder reaction as a key step.

The First Total Synthesis of Five Elegan Type Natural Products

The first total synthesis of five linear diterpenes: eleganolone (1), eleganolone acetate (2), elegandiol (3), eleganonal (4) and epoxyeleganolone (5), was achieved from (E,E)-farnesol (6) via 4 to 6 steps. The key step was the alkylation reaction of silyl cyanide with allylic iodide.

Determination of Air/Fuel and Steam/Fuel Ratio for Coal Gasification Process to Produce Synthesis Gas

In this study, a coal gasification model is developed based on nine simultaneous reactions. For given gasification temperature and pressure, the air/fuel and water vapor/fuel ratio are optimized for maximum H2/CO ratio by parametric study. Furthermore, the cold gas efficiency and higher heating value of the synthesis gas produced are computed for each case. Optimum locations of investigated parameters are also searched for maximizing cold gas efficiency and higher heating value of the synthesis gas.

Systematic Synthesis of Impacts of Climate Change on China's Crop Production System

Global climate change is real and already taking place. The most recent Fifth Assessment Report of the Intergov- ernmental Panel on Climate Change （IPCC AR5） stated that global land and ocean surface temperature increased by 0.85℃ over the period of 1880 to 2012 （IPCC Climate Change 2013）. China is among the most affected countries by global climate change.

Discovery and application of 6π-azaelectrocyclization to natural product synthesis and synthetic biology

While elucidating the inhibitory mechanism of a hydrolytic enzyme by aldehyde-containing natural product,we discovered a reaction involving a rapid 6π-azaelectrocyclization of azatrienes generated from aldehyde with lysine residues.The electrocyclic reaction of the 1-azatriene system,a cyclization precursor,exhibited a significant substituent effect.Asymmetric chiral piperidine synthesis and a one-pot library synthesis of pyridines on solid-supports were applied to synthesize pyridine/indole alkaloid-type natural product.Additionally,we developed lysine-based labeling and engineering of biomolecules and living cells based on the rapid 6π-azaelectrocyclization.Both labels and oligosaccharide structures were introduced efficiently and selectively into surface lysines under the mild conditions;notable effects of N-glycans on proteins and living cells were visualized for the first time by PET and noninvasive fluorescence imaging.

Enantioselective iridium-catalyzed allylic substitution with a Reformatsky reagent: direct construction of β-stereogenic homoallylic esters

The Reformatsky reagent derived from ethyl bromoacetate circumvents the challenge associated with the direct regio-and enantioselective iridium-catalyzed allylic alkylation with an unstabilized aliphatic ester enolate. Notably, this work represents the first example of using a Reformatsky reagent in a metal-allyl reaction, which permits the direct construction of enantioenriched β-stereogenic homoallylic esters without preactivation of the pronucleophile or post-reaction modification of the product(e.g., thermal decarboxylation of a 1,3-dicarbonyl). Moreover, the process allows the coupling of a broad range of sterically and electronically diverse electrophiles bearing aryl, heteroaryl and alkenyl derivatives, including the significantly more challenging alkyl-substituted allylic carbonates. The versatility of the ester product is exemplified by a series of functional group manipulations and the development of a concise and efficient enantioselective total synthesis of the natural product,(+)-descurainolide A. Finally, mechanistic studies indicate that the zinc enolate behaves as a soft nucleophile that undergoes outer-sphere alkylation.

Dinitrogen extrusion from diazene in organic synthesis

Radical-mediated reactions have many advantages in the construction of complex molecular scaffolds by forging chemical bonds of high challenge.Diazenes,including 1,1-diazenes and 1,2-diazenes,can generate biradical species via nitrogen extrusion under thermal or photochemical conditions.The superior reactivity of the generated biradical enables various types of synthetic transformations with excellent chemoselectivity and has been applied to the complex natural products synthesis.In this mini-review,the modes of reaction are summarized and discussed,namely ring contraction via nitrogen deletion,homo or heterodimerization,trimethylenemethane(TMM)-diyl cycloaddition.Applications of these classes of reactions in complex natural product synthesis are illustrated.Last but not least,the current state,future directions,and opportunities for dinitrogen extrusion reaction from diazenes are highlighted and discussed.

SEARCH FOR TRANSLESION SYNTHESIS MODULATORS FROM NATURAL PRODUCTS:ANALYTICAL DEVELOPMENT, VALIDATION AND APPLICATIONS

DNA translesion synthesis(TLS)is a DNA damage tolerance mechanism that relies on a series of specialized DNA polymerases able to bypass a lesion on a DNA template strand during replication or post-repair synthesis.TLS DNA polymerases pursue replication by inserting a base opposite this lesion,correctly or incorrectly

Efficient and collective total synthesis of natural products via radical cascade reactions

Subject Code:B02With the support of the National Natural Science Foundation of China,the research team led by Prof.Qin Yong(秦勇)at Sichuan University accomplished a collective synthesis of 33 monoterpenoid indole alkaloids that belong to four families,by developing new photoredox-initiated radical cascade reactions.

Asymmetric catalytic hydrogenation of imines and enamines in natural product synthesis

Asymmetric catalytic hydrogenations of imines and enamines with chiral transition-metal complexes bearing chiral ligands are among the most green and powerful approaches for the elaboration of chiral amine structures in organic synthesis.This review focuses on recent applications of asymmetric hydrogenations of imine and enamine substrates in the total syntheses of natural products.These applications include diverse processes involving asymmetric transfer hydrogenation(ATH)and asymmetric hydrogenation(AH)to form key chiral amine motifs in natural products with good efficiency and high-level enantiocontrol.

A synthesis method based on speech production and articulatory model

A method to synthesize formant targeted sounds based on speech production model and Reflection-Type Line Analog (RTLA) articulatory synthesis model is presented. The synthesis model is implemented with scattering process derived from a RTLA of vocal tract system according to the acoustic mechanism of speech production. The vocal-tract area function which controls the synthesis model is derived from the first three formant trajectories by using the inverse solution of speech production. The proposed method not only gives good naturalness and dynamic smoothness, but also is capable to control or modify speech timbres easily and flexibly. Further and mores it needs less number of control parameters and very low update rate of the parameters.

Total syntheses of bupleurynol and its analog

An efficient route to the natural products bupleurynol and its analog（RB-2）,isolated from Bupleuri Radix,was established based on versatile intermediate（15）.In this synthetic route,Sonogashira and CadiotChodkiewicz coupling as well as Julia-Kocienski olefination are utilized as key steps.The highly efficient synthetic route provides opportunities to explore the biological behavior of bupleurynol and RB-2.

A strategic study towards constructing the nine-membered azonane ring system of palhinine A via an azidoketol fragmentation reaction

A proposed strategy for constructing the nine-membered azonane ring system embedded in the isotwistane framework of palhinine A has been preliminarily studied on the basis of an azidoketol fragmentation reaction together with a SmI2-mediated pinacol coupling. Albeit negative results for building the azonane ring scaffold via a tertiary azidoketol fragmentation, the present exploration strategically provided an endeavor to probe the synthetically challenging issue in the synthetic study of palhinine A.