Article
Chemistry, Organic
Jatinder Singh, Garrison A. Nickel, Yu Cai, Dakota D. Jones, Tanner J. Nelson, Jeshurun E. Small, Steven L. Castle
Summary: O-phenyloximes tethered to alkenes undergo 5-exo-trig iminyl radical cyclizations upon microwave irradiation, resulting in the formation of various bonds. The versatile pyrroline adducts can be transformed into a range of different species. These cyclizations exhibit a broad scope and in some cases are highly diastereoselective.
Article
Chemistry, Multidisciplinary
Maximilian Scheruebl, Constantin G. Daniliuc, Armido Studer
Summary: The article introduces the application of arynes as radical acceptors, showing how the stable radical TEMPO can react with different ortho-substituted benzynes to generate aryl radicals for subsequent cyclizations, eventually being trapped by TEMPO. This method provides a novel approach for the convenient synthesis of various dihydrobenzofurans, oxindoles, and sultones.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Applied
R. Yu. Balakhonov, I. S. Mekeda, V. Z. Shirinian
Summary: A multifaceted study was conducted to investigate the effect of various factors on the efficiency of photocyclization of naphthofuran O-acyl oximes. It was found that DABCO can promote intramolecular cyclization with yields ranging from 34% to 87%, acting as both an electron transfer agent and a proton acceptor.
ADVANCED SYNTHESIS & CATALYSIS
(2023)
Article
Chemistry, Organic
Yingming Ren, Yaxin Ge, Qinqin Yan, Shiliu Chen, Yang Li, Lijun Li, Zhong-Quan Liu, Zejiang Li
Summary: The study explores a free radical-initiated cascade cyclization of unactivated alkenes with chloralkanes, providing a protocol for the synthesis of chlorinated heterocycles or polycyclic compounds through selective activation of the alpha-C(sp(3))-H bond of chloralkanes. Various radical inhibition experiments, radical capture operations, and radical clock tests were conducted in this system.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Organic
Cong Ye, Bao-Gui Cai, Juan Lu, Xiao Cheng, Lei Li, Zhong-Wen Pan, Jun Xuan
Summary: The method uses a blue-light LED to promote the coupling of aryl diazoacetates with sulfur ylides, featuring mild conditions, good functional group tolerance, and a broad substrate scope. Under optimal reaction conditions, a variety of trisubstituted olefins can be synthesized and further transformed into other important biologically active heterocycles.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Physical
Dong Yang, Jiaming Chen, Yanping Huang, Huiquan Pan, Jingqi Shi, Yingyue Zhang, Fang Wang, Ziyuan Li
Summary: A formal aza-Wacker cyclization utilizing a synergistic Cu/TEMPO-catalyzed radical relay pathway with NFSI as an external oxidant is reported, providing an efficient approach for the synthesis of oxazolidinones, pyrrolidones, and isoindolinones under mild conditions.
Article
Chemistry, Organic
Wenchang Li, Peng Zhou, Qing Zhao, Kejun Lin, Tingshun Zhu
Summary: An N-heterocyclic carbene-catalyzed cascade [3 + 2 + 1] annulation was developed for the synthesis of 1,3-oxazin-6-ones from vinyl azides, aldehydes, and trihalomethyl reagents. The cascade reaction involved NHC-catalyzed single electron transfer, addition of trihalomethyl radicals to vinyl azides, denitrogenated transformation into iminyl radicals, C-N radical coupling of iminyl radicals and ketyl radicals, and base-controlled dehalogenative cyclization.
ORGANIC & BIOMOLECULAR CHEMISTRY
(2023)
Article
Chemistry, Organic
Songeziwe Ntsimango, Kennedy J. Ngwira, Moira L. Bode, Charles B. de Koning
Summary: UV radiation was used to transform readily synthesized biphenyl-2-carbaldehyde O-acetyl oximes into phenanthridines, with the scope and limitations of this novel reaction explored. The methodology was successfully applied in the synthesis of trisphaeridine, achieving a 6.5% overall yield from 1-bromo-2,4,5-trimethoxybenzene in four linear steps.
BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Organic
Jatinder Singh, Spencer A. Jones, Tanner J. Nelson, Jesus A. Botello, Steven L. Castle
Summary: Microwave irradiation of O-phenyloximes leads to the N-O homolysis and 1,5-hydrogen atom transfer, resulting in the formal and gamma-C-H functionalization of ketones through the trapping of the radical intermediate and in situ imine hydrolysis. The Lewis acid InCl3 & BULL;H2O facilitates the hydrogen atom transfer, enabling the functionalization of benzylic and nonbenzylic secondary carbon atoms. Functionalization of primary carbon atoms is also feasible but with lower yields, requiring ClCH2CO2H as an additive instead of InCl3 & BULL;H2O. Both C-O and C-C bond formation can be achieved by this method.
JOURNAL OF ORGANIC CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Kun Jiang, Shi-Jun Li, Qing-Peng Liu, Ning Yu, Yu-Lin Li, Yu-Qiang Zhou, Kui-Cheng He, Jing Lin, Ting-Yu Zheng, Jian Lang, Yu Lan, Ye Wei
Summary: Bridged tetracyclic nitrogen scaffolds are commonly found in biologically active molecules and medicinally relevant structures. Traditional methods require complex reaction steps and/or specific starting materials. This study presents an unprecedented iminyl radical-triggered relay annulation from oxime-derived peresters and azadienes, which demonstrates good substrate scope, functional group compatibility, and the ability to deliver various bridged aza-tetracyclic compounds with complex molecular topology and four contiguous stereogenic centers in a single operation.
Article
Chemistry, Multidisciplinary
Feng Pan, Haohu Li, Xiaohua Wang, Liwen Luo, Yanfei Lin, Qingkai Yu, Wenlin Xie, Lianpeng Zhang
Summary: A general and convenient protocol for the visible light-promoted radical-mediated cascade spiro-cyclization/Michael addition of N-arylpropiolamides with thiophenols was developed. This method employs commercially available hydrochloric acid as a cheap promoter and air as a sustainable oxidant. The reaction conditions are tolerant towards many functional groups and produce sulfur-containing benzo[b]pyrrolo[2,1-c][1,4]oxazine-3,9-diones.
Article
Chemistry, Multidisciplinary
Austin D. Marchese, Andrew G. Durant, Cian M. Reid, Clara Jans, Ramon Arora, Mark Lautens
Summary: A Pd(0)/blue light catalyzed carboiodination reaction has been reported, which generates a variety of iodinated hetero- and carbocycles. The reaction system is simple and stable, and shows good tolerance towards sensitive functional groups, delivering products in high yields. Experimental evidence supports the reversible C-I bond formation via a single electron mechanism.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Organic
Yingming Ren, Qinqin Yan, Yang Li, Yongjun Gao, Jincan Zhao, Lijun Li, Zhong-Quan Liu, Zejiang Li
Summary: This study presents a persulfate-promoted reaction system for the synthesis of SCF3-substituted dibenzazepines or dioxodibenzothiazepines through the reaction of aryl acetylenes with AgSCF3. The final products were confirmed by single-crystal X-ray diffraction data. The reaction system was further explored through scaled-up experiments, additional transformations, and radical inhibition experiments.
JOURNAL OF ORGANIC CHEMISTRY
(2022)
Article
Chemistry, Organic
Yu-Song Ran, Bo Jiang, Yun-Tao Shen, Tai-Gang Fan, Wei Jiang, Cui Zhang, Ya-Min Li
Summary: A visible-light-promoted cascade cyclization reaction has been developed for the synthesis of tetrahydrobenzo[mn]cyclopenta[b]acridines using 3-ethynyl-[1,1'-biphenyl]-2-carbonitriles and unsaturated alpha-bromocarbonyls. This reaction involves the formation of three C(sp(3))-C(sp(2)) bonds, one C(sp(2))-N bond, and three cycles in a single step, through the addition of a C-centered radical to the carbon-carbon triple bond and subsequent radical cyclizations. The reaction conditions are mild, and the reaction shows a wide substrate scope and high efficiency in bond formation.
Article
Chemistry, Multidisciplinary
Youqing Yang, Constantin G. Daniliuc, Armido Studer
Summary: A radical 1,1,2-trifunctionalization of terminal alkynes is achieved using alkyl triflones as precursors and trapping reagents, with good yields of highly substituted cyclopentanes obtained at elevated temperatures using dibenzoyl peroxide or alpha,alpha '-azobisisobutyronitrile as initiators.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Organic
Ankur Jalan, David W. Kastner, Kei G. I. Webber, Mason S. Smith, Joshua L. Price, Steven L. Castle
Article
Chemistry, Multidisciplinary
Maxwell J. Moore, Shiwei Qu, Ceheng Tan, Yu Cai, Yuzo Mogi, D. Jamin Keith, Dale L. Boger
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2020)
Article
Chemistry, Multidisciplinary
Yu Cai, Zhiwei Ma, Jintao Jiang, Concordia C. L. Lo, Shi Luo, Ankur Jalan, Joseph M. Cardon, Alexander Ramos, Diego A. Moya, Daniel Joaquin, Steven L. Castle
Summary: The total synthesis of the anticancer peptide natural product yaku'amide A was achieved using regioselective aminohydroxylation for preparing beta-tert-hydroxy amino acids and a one-pot reaction for constructing E- and Z-Delta Ile residues. The process also involved anti dehydration, azide reduction, and O -> N acyl transfer without significant alkene isomerization, enabling a highly convergent and efficient synthetic route to the natural product.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Organic
Jatinder Singh, Garrison A. Nickel, Yu Cai, Dakota D. Jones, Tanner J. Nelson, Jeshurun E. Small, Steven L. Castle
Summary: O-phenyloximes tethered to alkenes undergo 5-exo-trig iminyl radical cyclizations upon microwave irradiation, resulting in the formation of various bonds. The versatile pyrroline adducts can be transformed into a range of different species. These cyclizations exhibit a broad scope and in some cases are highly diastereoselective.
Article
Chemistry, Organic
Jatinder Singh, Tanner J. Nelson, Samuel A. Mansfield, Garrison A. Nickel, Yu Cai, Dakota D. Jones, Jeshurun E. Small, Daniel H. Ess, Steven L. Castle
Summary: A detailed study on iminyl radical cyclizations of O-aryloximes tethered to alkenes is reported. The reactions can be initiated by either microwave irradiation or conventional heating, and various radical traps can be used to form C-C, C-N, C-O, C-S, or C-X bonds, resulting in functionalized pyrrolines. Allylic sulfide-containing substrates produce terminal alkenes through a tandem cyclization-thiyl radical beta-elimination pathway. The cyclization of hydroxylated substrates shows moderate diastereoselectivity, partly attributable to intramolecular hydrogen bonding. Computational studies suggest a potential role of thermodynamics in controlling the stereochemistry of cyclizations. The use of O-(p-tert-butylphenyl)oximes instead of O-phenyloximes as substrates allows for lower reaction temperatures and a one-pot oxime ether formation-cyclization under conventional heating. The resulting functionalized pyrrolines can be conveniently transformed in various ways.
JOURNAL OF ORGANIC CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Jingyao Wang, Mark R. Berglund, Timothy Braden, Matthew C. Embry, Martin D. Johnson, Stephen R. Groskreutz, Fareed Bhasha Sayyed, Sergey Vladimirovich Tsukanov, Timothy D. White, Ankur Jalan, Kevin D. Seibert, Michael E. Kopach
Summary: This study investigates the formation of diketopiperazine (DKP) during peptide synthesis and proposes control strategies to minimize DKP formation. DKP formation primarily occurs during specific reactions and post-coupling aging. Alternative protection methods and improved storage conditions are identified to enhance the stability of the peptide intermediates.
Article
Biochemical Research Methods
Mark A. Strege, Trent J. Oman, Donald S. Risley, Laura K. Muehlbauer, Ankur Jalan, Zhirui Jerry Lian
Summary: This article describes a chiral high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method for the rapid and accurate determination of amino acid chiral purity in peptides. The method involves hydrolysis of the peptide in deuterated acid, separation of the amino acids by chiral chromatography interfaced with ESI-MS/MS, and direct analysis of the samples using high-low chromatography and extraction of selected ion response. The method was validated for all nineteen chiral proteogenic amino acids and shown to be comparable to traditional testing methods through the analysis of four model peptides.
JOURNAL OF CHROMATOGRAPHY B-ANALYTICAL TECHNOLOGIES IN THE BIOMEDICAL AND LIFE SCIENCES
(2023)
Article
Chemistry, Multidisciplinary
Maxwell J. Moore, Pengjin Qin, D. Jamin Keith, Zhi-Chen Wu, Sunna Jung, Shreyosree Chatterjee, Ceheng Tan, Shiwei Qu, Yu Cai, Robyn L. Stanfield, Dale L. Boger
Summary: This paper presents a new simplified and expanded divergent total synthesis method for pocket-modified vancomycin analogs, which provides a common late-stage intermediate [Psi[C(=S)NH]Tpg(4)]vancomycin. Highlights of this approach include an atroposelective synthesis of [Psi[C(=S)NH]Tpg(4)]-vancomycin aglycon, a one-pot enzymatic glycosylation for direct conversion to [Psi[C(=S)NH]Tpg(4)]vancomycin, and new methods for late-stage conversion of the embedded thioamide to amidine/aminomethylene pocket modifications. In addition, the potent antimicrobial activity of the new amidine-based maxamycins is demonstrated, showing equipotent activity against both vancomycin-sensitive and vancomycin-resistant Gram-positive organisms.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Meeting Abstract
Biochemistry & Molecular Biology
Ankur Jalan, David W. Kastner, Kei G. I. Webber, Steven Castle
JOURNAL OF PEPTIDE SCIENCE
(2018)
Meeting Abstract
Chemistry, Multidisciplinary
David Kastner, Ankur Jalan, Steven Castle
ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY
(2017)
Meeting Abstract
Chemistry, Multidisciplinary
Ankur Jalan
ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY
(2017)
Meeting Abstract
Chemistry, Multidisciplinary
Kei Webber, Ankur Jalan, Steven Castle
ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY
(2017)
Meeting Abstract
Chemistry, Multidisciplinary
Ankur Jalan, Steven Castle
ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY
(2016)
