Kinetic Resolution of Allylic Alcohol with Chiral BINOL-Based Alkoxides: A Combination of Experimental and Theoretical Studies

Liu, Yidong,Liu, Song,Li, Dongmei,Zhang, Nan,Peng, Lei,Ao, Jun,Song, Choong Eui,Lan, Yu,Yan, Hailong American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.2

<P>The development and characterization of enantioselective catalytic kinetic resolution of allylic alcohols through asymmetric isomerization with chiral BINOL derivatives-based alkoxides as bifunctional Brønsted base catalysts were described in the study. A number of chiral BINOL derivatives-based alkoxides were synthesized, and their structure-enantioselectivity correlation study in asymmetric isomerization identified a promising chiral Brønsted base catalyst, which afforded various chiral secondary allylic alcohols (ee up to 99%, <I>S</I> factor up to >200). In the mechanistic study, alkoxide species were identified as active species and the phenol group of BINOL largely affected the high reactivity and enantioselectivity via hydrogen bonding between the chiral Brønsted base catalyst and substrates. The strategy is the first successful synthesis strategy of various chiral secondary allylic alcohols through enantioselective transition-metal-free base-catalyzed isomerization. The applicability of the strategy had been demonstrated by the synthesis of the bioactive natural product (+)-veraguensin.</P> [FIG OMISSION]</BR>

Contribution of Aboveground Litter Decomposition to Soil Respiration in a Subtropical Coniferous Plantation in Southern China

Yidong Wang,Huimin Wang,Zeqing Ma,Wuefa Wen,Qingkang Li,Yunfen Liu,Wiaomin Sun,Guirui Yu 한국기상학회 2009 Asia-Pacific Journal of Atmospheric Sciences Vol.45 No.2

Soil CO₂ efflux (RS) was monitored in a 23-year-old subtropical coniferous plantation in southern China from January 2004 to December 2006. Field measurements of RS with litterfall (CK) and without litterfall (NL) were conducted to evaluate the contribution of aboveground litter decomposition to RS. The results indicated that annual RS from CK ranged from 11.5 mg (C) m<SUP>-2</SUP>h<SUP>-1</SUP> in 2004 to 186.2 ㎎ (C) m<SUP>-2</SUP>h<SUP>-1</SUP> in 2006. The RS of NL was significantly lower than the RS of CK. RS was mainly determined by soil temperature (TS), but it was also affected by soil moisture. Together, both factors explained > 70%of the observed variations in RS. The temperature sensitivity (Q<SUB>10</SUB>) of RS from NLwas lower than that from CK by considering the soil moisture effect. On average, the annual RS of the coniferous plantation was estimated to be 669 g (C)m<SUP>-2</SUP>yr<SUP>-1</SUP> over the study period. The litterfall greatly enhanced the RS, and the respiration from aboveground litter accounted for about 33% of the total RS, in which the fresh litterfall decomposition accounted for a large proportion. The carbon pool of aboveground litter in this young conifer forest is expected to increase continuously.

QuickForm Simulation System of Sheet Metal Forming with Trial-and-error Contact Algorithm

Bao Yidong,Liu Lei,Lu Yu,Chen Wenliang 한국소성가공학회 2011 기타자료 Vol.2011 No.8

The QuickForm numerical simulation system has been self-developed specially for sheet metal forming with complex geometries. In order to resolve the convergence problem of static implicit method due to the change of contact state, the uncoupling solution method of the non-linear differential equations is used in QucikForm system. The bending effect and drawing effect during forming procedure are separated into two independent processes in QuickForm system. During bending effect solution, the contact state between the blank nodes and rigid tools should be determined by accurate contact algorithm. A trial-and-error contact algorithm is used in the bending effect calculation process of QuickForm system. The contact procedure is carried out before the solving of bending effect FEM equations, and the contact conditions are treated as the boundary conditions of FEM equations. Numerical simulation results of complex part demonstrate the higher efficiency and accuracy of this contact algorithm and the proposed special purpose program.

Fluoride Anions in Self-Assembled Chiral Cage for the Enantioselective Protonation of Silyl Enol Ethers

Paladhi, Sushovan,Liu, Yidong,Kumar, B. Senthil,Jung, Min-Jung,Park, Sang Yeon,Yan, Hailong,Song, Choong Eui THE AMERICAN CHEMICAL SOCIETY 2017 ORGANIC LETTERS Vol.19 No.12

<P>The potential of Song's chiral oligoethylene glycol's (oligoEGs) as catalysts was explored in the enantioselective protonation of trimethylsilyl enol ethers in combination with alkali metal fluoride (KF and CsF) and in the presence of a proton source Highly enantioselective protonatigns of various silyl enol ethers of alpha-substituted tetralohes were achieved, producing chiral alpha-substituted-Jetralones in full conversion and with up to 99% ee. The established protocol was successfully exiended to the synthesis of biologically relevant chiral alpha-substituted chromanone and thiothromarione derivatives.</P>

Quantitative Evaluation of Coal Structures with the Aid of Geophysical Logging Data

Teng Juan,Liu Dameng,Yao Yanbin,Cai Yidong 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.4

Coal structure not only is a significant physical parameter of the coal reservoirs, but also has an effect on the coalbed methane (CBM) productivity during coal mining. In this paper, the clustering method is used to evaluate the coal structures quantitatively. For better application on the identification process of the coal structures, the clustering method is modified twice by ascertaining initial clustering centers and calibrating Euclidean distances, respectively. The quantitative method was applied to evaluate coal structures in 16 CBM wells in the Zhengzhuang field, Southern Qinshui Basin, North China. Results show that coal structures by the twice modified clustering method has good accordance with that by the coring samples. Therefore, coal structure identification using clustering method with the aid of geophysical logging data is feasible in the study area. The thickness proportions of coal structures have positive/ negative relationships with the corresponding average logging data. The multiple linear regression method was employed to predict the thickness proportions of coal structures. The predicted results show that prediction models of thickness proportions of coal structures are feasible to predict the distribution of coal structures fast in spite of the limited errors.

Asymmetric Synthesis of Trisubstituted Tetrahydrothiophenes via in Situ Generated Chiral Fluoride-Catalyzed Cascade Sulfa-Michael/Aldol Reaction of 1,4-Dithiane-2,5-diol and α,β-Unsaturated Ketones

Duan, Mengying,Liu, Yidong,Ao, Jun,Xue, Lu,Luo, Shilong,Tan, Yu,Qin, Wenling,Song, Choong Eui,Yan, Hailong American Chemical Society 2017 ORGANIC LETTERS Vol.19 No.9

<P>A chiral, fluoride-catalyzed asymmetric cascade sulfaMichael/aldol condensation reaction of 1,4-dithiane-2,5-diol and a series of alpha,beta-unsaturated ketones is described to access chiral trisubstituted tetrahydrothiophene derivatives. The target products, including the spiro tetrahydrothiophene derivatives bearing a five-, six-, and seven-membered ring, were highly functionalized and showed high ee value. This established protocol realized a highly enantioselective reaction with a catalytic amount of KF and Song's chiral oligoEG via in situ generated chiral fluoride to construct useful heterocyclic skeletons with great complexity.</P>

Corrosion Cracking Process of Reinforced Concrete under the Coupled Effects of Chloride and Fatigue Loading

Jiansheng Shen,Junzhe Liu,Yidong Xu,Kanghao Jia,Fangyu Wu,Wei Chen,Dayong Zhu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.9

To study the corrosion cracking process of reinforced concrete under the combined effects of chloride and fatigue loading, the constan-current and dry-wet cycle accelerated corrosion method was used to corrosion the specimens under different stress levels for different time. The quality loss of reinforcement, the composition of corrosion products and the cracking of concrete are analyzed from the macro, micro and micro scales, and to obtain the spatial distribution as well as microscopic characteristics of corrosion products of the reinforcement bar under coupling conditions. Additionally, a model of steel rust cracking under the coupled action of chloride and fatigue loading is established. The results show that: under the same corrosion time, the concrete cracking and steel corrosion degree become more serious with the increase of stress level. The greater the stress level, the earlier corrosion occurs and the more corrosion products are, Moreover, due to the fatigue load, the concrete on the upper side of the steel bar has rust expansion cracks earlier than the lower side.

Enantioselective Synthesis of <i>anti</i>–<i>syn</i>-Trihalides and <i>anti</i>–<i>syn</i>–<i>anti</i>-Tetrahalides via Asymmetric β-Elimination

Tan, Yu,Luo, Shilong,Li, Dongmei,Zhang, Nan,Jia, Shiqi,Liu, Yidong,Qin, Wenling,Song, Choong Eui,Yan, Hailong American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.18

<P>Structural motifs containing contiguous halide bearing stereocenters are common in natural products as well as bioactive molecules. A few successful examples have been reported in the area of asymmetric vicinal dihalogenation of alkenes for accessing dihalogenated products; in this report, an alternative generation method of contiguous halide-bearing stereocenters alpha,beta,gamma,delta relative to carbonyl group in excellent enantioselectivity is proposed by utilizing a Song's oligoEG catalyst-catalyzed asymmetric beta-elimination. According to this methodology, a wide range of anti-syn-trihalides and anti-syn-anti-tetrahalides with high levels of enantioselectivity were synthesized. The synthetic utility of the contiguous halide-bearing stereocenters was demonstrated by several transformations. The results of high-resolution mass spectrometry indicated that the favorable interaction between catalyst and one of the enantiomers of racemic contiguously multihalogenated ketone contributed to the original enantioselectivity of dehydrohalogenation. A deuterium kinetic isotope effect experiment revealed that this beta-elimination reaction proceeds by the E2 mechanism. This strategy opens a new pathway for the asymmetric synthesis of contiguous halide bearing stereocenters of great complexity.</P>

Mitogen-activated protein kinase 3 and 6 regulate <i>Botrytis cinerea</i>-induced ethylene production in Arabidopsis

Han, Ling,Li, Guo-Jing,Yang, Kwang-Yeol,Mao, Guohong,Wang, Ruigang,Liu, Yidong,Zhang, Shuqun Blackwell Publishing Ltd 2010 The Plant journal Vol.64 No.1

<P>Summary</P><P>Plants challenged by pathogens, especially necrotrophic fungi such as <I>Botrytis cinerea</I>, produce high levels of ethylene. At present, the signaling pathways underlying the induction of ethylene after pathogen infection are largely unknown. MPK6, an Arabidopsis stress-responsive mitogen-activated protein kinase (MAPK) was previously shown to regulate the stability of ACS2 and ACS6, two type I ACS isozymes (1-amino-cyclopropane-1-carboxylic acid synthase). Phosphorylation of ACS2 and ACS6 by MPK6 prevents rapid degradation of ACS2/ACS6 by the 26S proteasome pathway, resulting in an increase in cellular ACS activity and ethylene biosynthesis. Here, we show that MPK3, which shares high homology and common upstream MAPK kinases with MPK6, is also capable of phosphorylating ACS2 and ACS6. In the <I>mpk3</I> mutant background, ethylene production in gain-of-function <I>GVG-NtMEK2</I><SUP><I>DD</I></SUP> transgenic plants was compromised, suggesting that MPK6 and MPK3 function together to stabilize ACS2 and ACS6. Using a liquid-cultured seedling system, we found that <I>B. cinerea</I>-induced ethylene biosynthesis was greatly compromised in <I>mpk3/mpk6</I> double mutant seedlings. In contrast, ethylene production decreased only slightly in the <I>mpk6</I> single mutant and not at all in the <I>mpk3</I> single mutant, demonstrating overlapping roles for these two highly homologous MAPKs in pathogen-induced ethylene induction. Consistent with the role of MPK3/MPK6 in the process, mutation of <I>ACS2</I> and <I>ACS6</I>, two genes encoding downstream substrates of MPK3/MPK6, also reduced <I>B. cinerea</I>-induced ethylene production. The residual levels of ethylene induction in the <I>acs2/acs6</I> double mutant suggest the involvement of additional ACS isoforms, possibly regulated by MAPK-independent pathway(s).</P>