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Catalytic properties of 4,5-bridged proline methano- and ethanologues in the Hajos-Parrish intramolecular aldol reaction

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Organic Chemistry Frontiers 2022年第3期9卷 649-659页

作者： Sofiane Hocine Gilles Berger k.n.houk Stephen Hanessian aDepartment of Chemistry Universitéde MontréalStation Centre-VilleC.P.6128MontrealQCH3C 3J7Canada Microbiology Bioorganic&Macromolecular ChemistryFaculty of PharmacyUniversitéLibre de BruxellesBd du Triomphe1050 BrusselsBelgium Department of Chemistry and Biochemistry University of CaliforniaLos AngelesCA 90095-1569USA

The catalysis of the Hajos-Parrish reaction by cis-and trans-4,5-ethano-proline was explored experimentally and computationally with DFT(ωB97X-D and Mn15)and DLPnO-CCSD(T).Both of the new catalysts are as active as proline or cis-and trans-4,5-methano-proline,with the trans-ethano-proline being as enantioselective as proline.A thorough theoretical analysis of the electronic factors influencing catalysis is reported.

关键词： CCSD(T) proline catalysis

The role of Cul in the siloxane-mediated Pd-catalyzed cross-coupling reactions of aryl iodides with aryl lithium reagents

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Chinese Chemical Letters 2021年第1期32卷 441-444页

作者： Yu Chen Xiao Zhang Fang Liu Gucheng He Ju Zhang k.n.houk Amos BSmith III Yong Liang State key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic MaterialsSchool of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China Department of Chemistry University of PennsylvaniaPA 19104United States Department of Chemistry and Biochemistry University of CaliforniaCA 90095United States

Experiments indicate that a catalytic amount of Cul plays an important role in the siloxane-mediated Pd-catalyzed cross-coupling reactions with the direct use of organolithium *** of organolithium to the siloxane transfer agent generates an organosilicon *** calculations indicate that Cul initially accelerates the Si-Pd(Ⅱ) transmetalation of the organosilicon intermediate by the formation of CuI_(2)^(-).Subsequently,CuI_(2)^(-)works as a shuttle between the Si-Cu(Ⅰ) and Cu(Ⅰ)-Pd(Ⅱ)transmetalation processes.

关键词： Cross-coupling CuI DFT calculation Reaction mechanism Transmetalation

An DFT Study on the Mechanism of Wender's [Rh(CO)2Cl]2-catalyzed(5+2)Reactions

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An DFT Study on the Mechanism of Wender's [Rh(CO)2Cl]2-catal...

中国化学会第十三届金属有机化学学术讨论会

作者： Paul A.Wender k.n.houk Department of Chemistry Stanford University Department of Chemistry and Biochemistry University of CaliforniaLos Angeles

DFT calculations have been applied to investigate the reaction mechanism of rhodium dimer, [Rh(CO)2Cl]2, catalyzed (5+2) reactions between vinylcyclopropanes and alkynes. The catalytic species is Rh(CO)Cl and the catalytic cycle is through the sequential reactions of cyclopropyl cleavage of vinylcyclopropane, alkyne insertion (rate determining step), and a migratory reductive elimination (Yu, Z.-X.;Wender, P. A.;houk, k. n. J. Am. Chem. Soc. 2004,126, 9154).

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Diazo Esters as Dienophiles in Intramolecular（4+2） Cycloadditions: Computational Explorations of Mechanism

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Diazo Esters as Dienophiles in Intramolecular（4+2） Cycload...

第十三届全国量子化学会议

作者： Abing Duan Peiyuan Yu Fang Liu Feng Long Gu k.n.houk key Laboratory of Theoretical Chemistry of Environment Ministry of Education School of Chemistry and EnvironmentSouth China Normal University Department of Chemistry and Biochemistry University of California

The first experimental examples of Diels–Alder（DA）reactions of diazo compounds as heterodienophiles with dienes have been studied with density functional theory（DFT） using the M06-2X functional. For comparison, the reactivities of diazo esters as dienophiles or 1,3-dipoles with 1,3-dienes in intermolecular model systems have been analyzed by the distortion/interaction（D/I） model. The 1,3-dipolar cycloaddition is strongly favored for the intermolecular system. The intramolecular example is unique because the tether strongly favors the（4+2） cycloaddition.

关键词： DA 1,3-Dipolar DFT Diazo esters Diene D/I

Mechanism and Origins of Enantioselectivities in Spirobiindane-based Hypervalent Iodine（Ⅲ） Induced Asymmetric Dearomatizing Spirolactonizations

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Mechanism and Origins of Enantioselectivities in Spirobiinda...

中国化学会·第十三届全国物理有机化学学术会议

作者： Hanliang Zheng Yueqian Sang k.n.houk Xiao-Song Xue Jin-Pei Cheng State key Laboratory of Elemento-Organic Chemistry College of Chemistry Nankai University Department of Chemistry and Biochemistry University of California Los Angeles

＜正＞Dearomatization of phenols is a powerful strategy for the synthesis of complex molecules,providing an avenue for simultaneously introducing stereochemical information and generating products that are primed for ...

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Mechanism and Origins of Chemo-and Stereoselectivities of Aryl Iodide-Catalyzed Asymmetric Difluorinations of β-Substituted Styrenes

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Mechanism and Origins of Chemo-and Stereoselectivities of Ar...

中国化学会第十五届全国氟化学会议

作者： Biying Zhou Moriana k.Haj Eric n.Jacobsen k.n.houk Xiao-Song Xue State key Laboratory of Elemento-Organic Chemistry College of ChemistryNankai University Department of Chemistry&Chemical Biology Harvard UniversityCambridge Department of Chemistry and Biochemistry University of CaliforniaLos Angeles

The mechanism of the aryl iodide-catalyzed asymmetric migratory geminal difluorination of β-substituted styrenes

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Structural basis for stereoselective dehydration and hydrogen-bonding catalysis by the SAM-dependent pericyclase LepI

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Structural basis for stereoselective dehydration and hydroge...

第十一届全国化学生物学学术会议

作者： Yujuan Cai Yang Hai Masao Ohashi Cooper S.Jamieson Marc Garcia-Borras k.n.houk Jiahai Zhou Yi Tang State key Laboratory of Bio-organic and natural Products Chemistry Center for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryCAS Department of Chemistry and Biochemistry Department of Chemical and Biomolecular EngineeringUniversity of California Los Angeles

LepI is an S-adenosylmethionine（SAM）-dependent pericyclase that catalyses the formation of 2-pyridone natural product leporin C. Biochemical characterization has shown that LepI can catalyse stereoselective dehydration to yield a reactive（E）-quinone methide that can undergo bifurcating intramolecular Diels–Alder（IMDA） and hetero-Diels–Alder（HDA） cyclizations from an ambimodal transition state, as well as a [3,3]-retro-Claisen rearrangement to recycle the IMDA product into leporin C. Here, we solve the X-ray crystal structures of SAM-bound LepI and in complex with a substrate analogue（the product leporin C） and a retro-Claisen reaction transition-state analogue to understand the structural basis for the multitude of reactions. Structural and mutational analysis reveals how nature evolves a classic methyltransferase active site into one that can serve as a dehydratase and a multifunctional pericyclase. Catalysis of both sets of reactions employs H133 and R295, two activesite residues that are not found in canonical methyltransferases. An alternative role of SAM, which is not found to be in direct contact with the substrate, is also proposed.

关键词： pericyclase crystal structure SAM

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天然产物中硫代羧酸基团的生物合成机制研究

天然产物中硫代羧酸基团的生物合成机制研究

第十一届全国化学生物学学术会议

作者：董廖斌 Jeffrey D.Rudolf 黄勇 k.n.houk 段燕文 Ben Shen Department of Chemistry The Scripps Research Institute 中国药科大学湘雅国际转化医学联合研究院中南大学 Department of Chemistry and Biochemistry University of California

平板霉素和平板素是从土壤链霉菌中发现的两种强效萜类抗生素,具有独特的抑制细菌脂肪酸合酶活性。含有硫代羧酸基团的天然产物仅有三例报道,报告人从平板霉素高产菌中意外地获得含有硫代羧酸基团的硫代平板霉素和硫代平板素,并确定了... 详细信息

平板霉素和平板素是从土壤链霉菌中发现的两种强效萜类抗生素,具有独特的抑制细菌脂肪酸合酶活性。含有硫代羧酸基团的天然产物仅有三例报道,报告人从平板霉素高产菌中意外地获得含有硫代羧酸基团的硫代平板霉素和硫代平板素,并确定了平板霉素和平板素是硫代平板霉素和硫代平板素的非酶水解产物。通过研究发现,硫代羧酸基团的形成与一个由ptmA3和ptmU4功能基因组成的"硫代酸盒"直接相关;乙酰辅酶A合成酶(PtmA3)和辅酶A转移酶(PtmU4)分别负责利用辅酶A激活苯甲酸衍生物和从硫载体蛋白(sulfur-carrier proteins)转移硫代羧酸基团(图一)。PtmU4含有独特的双功能域,且其功能显著区别于经典的辅酶A转移酶在小分子羧酸之间可逆地转移辅酶A,是一类新型辅酶A转移酶的典型代表。另外,与平板霉素和平板素相比,硫代平板霉素和硫代平板素具有与抗菌作用靶点脂肪酸合酶更强的亲和力(≥2倍),为开发基于硫代羧酸药效团的新型抗生素提供了理论支撑;同时,特征性"硫代酸盒"的发现为挖掘更多含有硫代羧酸药效团的活性天然产物奠定了基础。

关键词：含硫天然产物碳-硫键生物合成硫代羧酸药效团平板霉素平板素

Gated container molecules

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Science China Chemistry 2011年第12期54卷 2038-2044页

作者： houk k.n. Department of Chemistry and Biochemistry University of California at Los AngelesLos Angeles

Donald J. Cram, the great UCLA chemist, received the nobel Prize for his discoveries about host-guest complexes . Both theoretical and experimental studies have been conducted about the nature and strength of interactions between the host and guest molecules. The concepts of constrictive binding （the activation energy of the binding process） and intrinsic binding （the free energy difference between the complex and the free host and guest molecules） were introduced to characterize different binding properties （Figure 1）

关键词：客体分子容器闸门主客体配合物加州大学诺贝尔奖相互作用结合特性