Thomas Magauer

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Co-reporter:Cedric L. Hugelshofer
Natural Product Reports (1984-Present) 2017 vol. 34(Issue 3) pp:228-234
Publication Date(Web):2017/03/17
DOI:10.1039/C7NP00005G
Covering: up to January 2017 This highlight article presents some recent examples of dyotropic rearrangements, which were applied in natural product total synthesis or proposed to occur in biosyntheses. The implementation of dyotropic reactions in the preparation of complex natural products has resulted in the development of elegant synthetic routes, and thereby highlights the utility of these powerful, yet relatively underrepresented, transformations.
Co-reporter:Cedric L. Hugelshofer
Organic & Biomolecular Chemistry 2017 vol. 15(Issue 1) pp:12-16
Publication Date(Web):2016/12/20
DOI:10.1039/C6OB02488B
Nature's highly efficient routes for constructing natural products have inspired chemists to mimic these processes in a laboratory setting. This Perspective presents some recent examples of conceptually different bioinspired total syntheses of complex terpenoids and thereby aims to highlight the vast benefits offered by bioinspired strategies.
Co-reporter:Cedric L. Hugelshofer
Journal of the American Chemical Society 2016 Volume 138(Issue 20) pp:6420-6423
Publication Date(Web):May 9, 2016
DOI:10.1021/jacs.6b03720
We have developed the first synthesis of the unique oxetane containing diterpene (+)-dictyoxetane. Our retrosynthetic planning was guided by the putative biosynthesis of the unprecedented 2,7-dioxatricyclo[4.2.1.03,8]nonane ring system. A bioinspired 4-exo-tet, 5-exo-trig cyclization sequence enabled the construction of the synthetically challenging dioxatricyclic framework. The overall synthesis proceeds in 15 linear steps from a known and readily available trans-hydrindane fragment. In addition, we were able to realize the first dyotropic rearrangement of an epoxide–oxetane substrate.
Co-reporter:Adriana S. Grossmann and Thomas Magauer  
Organic & Biomolecular Chemistry 2016 vol. 14(Issue 24) pp:5377-5389
Publication Date(Web):2016/01/26
DOI:10.1039/C6OB00091F
This review highlights the chemistry of trihaloethene building blocks with a special focus on commercially available 1,1,2-trichloroethene. The topics surveyed herein include the use of trihaloethenes as C2-building blocks for transition metal-catalyzed coupling reactions, addition, elimination and cycloaddition reactions as well as natural product syntheses.
Co-reporter:M.Sc. Teresa A. Unzner;M.Sc. Adriana S. Grossmann ;Dr. Thomas Magauer
Angewandte Chemie International Edition 2016 Volume 55( Issue 33) pp:9763-9767
Publication Date(Web):
DOI:10.1002/anie.201605071

Abstract

We report the synthesis of orthogonally functionalized naphthalenes from simple, commercially available indanones in four steps. The developed method proceeds through a two-step process that features a thermally induced fragmentation of a cyclopropane indanone with simultaneous 1,2-chloride shift. Migration of the chloride substituent occurs in a regioselective manner to preferentially afford the para-chloronaphthol substitution pattern. The obtained naphthols are versatile building blocks that can be selectively modified and used for the efficient construction of biologically active molecules. This has enabled the total synthesis of the potent anticancer natural product chartarin through a highly convergent retrosynthetic bond disconnection.

Co-reporter:M.Sc. Teresa A. Unzner;M.Sc. Adriana S. Grossmann ;Dr. Thomas Magauer
Angewandte Chemie 2016 Volume 128( Issue 33) pp:9915-9919
Publication Date(Web):
DOI:10.1002/ange.201605071

Abstract

We report the synthesis of orthogonally functionalized naphthalenes from simple, commercially available indanones in four steps. The developed method proceeds through a two-step process that features a thermally induced fragmentation of a cyclopropane indanone with simultaneous 1,2-chloride shift. Migration of the chloride substituent occurs in a regioselective manner to preferentially afford the para-chloronaphthol substitution pattern. The obtained naphthols are versatile building blocks that can be selectively modified and used for the efficient construction of biologically active molecules. This has enabled the total synthesis of the potent anticancer natural product chartarin through a highly convergent retrosynthetic bond disconnection.

Co-reporter:Cedric L. Hugelshofer
Journal of the American Chemical Society 2015 Volume 137(Issue 11) pp:3807-3810
Publication Date(Web):March 13, 2015
DOI:10.1021/jacs.5b02021
A highly efficient strategy enabled the asymmetric total synthesis of 15 antifeedant leucosceptroid natural products. The advanced tricyclic core, available in gram quantity, served as the pivotal intermediate for the preparation of norleucosceptroids B, C, F, and G and leucosceptroids A, B, G, I, J, L, and M. Additionally, the bioinspired oxidative transformation of leucosceptroid A to leucosceptroids C, K, O, and P using singlet oxygen supports the hypothesis that leucosceptroids A and B are most likely the biogenetic precursors of all other members of this natural product family.
Co-reporter:Klaus Speck, Konstantin Karaghiosoff, and Thomas Magauer
Organic Letters 2015 Volume 17(Issue 8) pp:1982-1985
Publication Date(Web):March 31, 2015
DOI:10.1021/acs.orglett.5b00738
The development of a sequential O–H/C–H bond functionalization of phenols initiated by the cationic gold(I)-catalyzed cyclization of 1-bromo-1,5-enynes to produce (2-bromocyclopent-2-en-1-yl)phenols is reported. This unprecedented domino transformation efficiently proceeds under mild conditions (5 mol % of (t-Bu)3PAuNTf2, CH2Cl2, 0–23 °C) via an intermediate aryl alkyl ether which collapses at ambient temperature to undergo a 1,2-hydride shift followed by C–H insertion of the phenol.
Co-reporter:Teresa A. Unzner, Thomas Magauer
Tetrahedron Letters 2015 Volume 56(Issue 7) pp:877-883
Publication Date(Web):11 February 2015
DOI:10.1016/j.tetlet.2014.12.145
The synthesis of fluorinated compounds as well as the use of these products as building blocks for the preparation of complex molecules are fast growing research areas. Herein we highlight recent progress in the activation of allylic and benzylic C–F bonds for the synthesis of functionalized molecules. SN2′ reactions of allylic difluoro and trifluoro compounds as well as transition-metal-catalyzed (nickel, palladium, platinum and copper) processes are described. The C–F bond activation of 3-fluoropropenes was achieved with platinum- or organocatalysis. Benzylic C–F bond activation was realized with magnesium by deprotonation leading to the formation of reactive quinone methide intermediates and with hydrogen bond donors by forming strong F⋯H interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:Johannes Feierfeil;Adriana Grossmann ;Dr. Thomas Magauer
Angewandte Chemie 2015 Volume 127( Issue 40) pp:12001-12004
Publication Date(Web):
DOI:10.1002/ange.201506232

Abstract

Described is the development of a highly efficient 2π disrotatory ring-opening aromatization sequence using bicyclo[3.1.0]hexan-2-ones. This unprecedented transformation efficiently proceeds under thermal conditions and allows facile construction of uniquely substituted and polyfunctionalized benzoates. In the presence of either amines or alcohols formation of substituted anilines or ethers, respectively, is achieved. Additionally, the utility of this method was demonstrated in a short synthesis of sekikaic acid methyl ester.

Co-reporter:Johannes Feierfeil;Adriana Grossmann ;Dr. Thomas Magauer
Angewandte Chemie International Edition 2015 Volume 54( Issue 40) pp:11835-11838
Publication Date(Web):
DOI:10.1002/anie.201506232

Abstract

Described is the development of a highly efficient 2π disrotatory ring-opening aromatization sequence using bicyclo[3.1.0]hexan-2-ones. This unprecedented transformation efficiently proceeds under thermal conditions and allows facile construction of uniquely substituted and polyfunctionalized benzoates. In the presence of either amines or alcohols formation of substituted anilines or ethers, respectively, is achieved. Additionally, the utility of this method was demonstrated in a short synthesis of sekikaic acid methyl ester.

Co-reporter:Tatjana Huber, Daniel Kaiser, Jens Rickmeier, and Thomas Magauer
The Journal of Organic Chemistry 2015 Volume 80(Issue 4) pp:2281-2294
Publication Date(Web):January 26, 2015
DOI:10.1021/jo502809d
Here we describe the realization of a one-pot protocol for the β-C–H halogenation of cyclic enones via umpolung of the β-carbon. The developed method includes hydrazone formation and selective β-halogenation (bromination, chlorination) with N-bromosuccinimide and Palau’chlor (2-chloro-1,3-bis(methoxycarbonyl)guanidine) followed by hydrolysis of the hydrazone moiety. Using the optimized conditions, we were able to effectively β-brominate and β-chlorinate for the first time cyclic enones with different substitution patterns and various functional groups in one flask, whereas previous methods for this transformation required several steps. Additionally, the utility of the method was demonstrated in a short synthesis of the core structure of the Aspidosperma alkaloid jerantinine E.
Co-reporter:Shi-Hong Luo, Cedric L. Hugelshofer, Juan Hua, Shu-Xi Jing, Chun-Huan Li, Yan Liu, Xiao-Nian Li, Xu Zhao, Thomas Magauer, and Sheng-Hong Li
Organic Letters 2014 Volume 16(Issue 24) pp:6416-6419
Publication Date(Web):December 4, 2014
DOI:10.1021/ol503230s
Seven new leucosceptroid degradation products possessing a C20, C21, or C25 framework, norleucosceptroids D–H (1–5), leucosceptroids P (6), and Q (7), have been isolated from Leucosceptrum canum. Their structures were determined by comprehensive NMR, MS, and single-crystal X-ray diffraction analyses. Discovery of these key intermediates, together with the biomimetic oxidation of a model system, supports the hypothesis that two biosynthetic pathways are operative. Antifeedant activity was observed for compounds 1–3.
Co-reporter:M.Sc. Cedric L. Hugelshofer ;Dr. Thomas Magauer
Angewandte Chemie International Edition 2014 Volume 53( Issue 42) pp:11351-11355
Publication Date(Web):
DOI:10.1002/anie.201407788

Abstract

The first asymmetric total synthesis of the antifeedant terpenoids (+)-norleucosceptroid A, (−)-norleucosceptroid B, and (−)-leucosceptroid K has been accomplished. This highly concise synthetic route was guided by our efforts to develop a platform for the collective synthesis of a whole family of antifeedant natural products. The synthesis features a Hauser–Kraus-type annulation followed by an unprecedented, highly efficient intramolecular dilactol aldol-type condensation reaction to produce the 5,6,5 skeleton. The developed synthetic route proceeds for norleucosceptroid A and B in 16 steps (longest linear sequence) from known compounds.

Co-reporter:Jeffrey M. Hammann;Teresa A. Unzner ;Dr. Thomas Magauer
Chemistry - A European Journal 2014 Volume 20( Issue 22) pp:6733-6738
Publication Date(Web):
DOI:10.1002/chem.201402098

Abstract

Herein, we describe a transition-metal-free protocol for the conversion of simple 2-allyl-3-(trifluoromethyl)phenols into substituted 5-fluoronaphthalen-1-ols. The key events of this reaction include the selective activation of two CF bonds and formation of an intermediate hexatriene system, which undergoes a 6π electrocyclization, followed by rearomatization. This concept enables the rapid conversion (three steps) of various commercially available 3-(trifluoromethyl)phenols into novel fluorine-containing naphthols, which are difficult to prepare by previous methods. The reported sequence was also extended to a one-pot transformation of 3-(trifluoromethyl)phenols into 5-fluoronaphthalen-1-ols.

Co-reporter:M.Sc. Cedric L. Hugelshofer ;Dr. Thomas Magauer
Angewandte Chemie 2014 Volume 126( Issue 42) pp:11533-11537
Publication Date(Web):
DOI:10.1002/ange.201407788

Abstract

The first asymmetric total synthesis of the antifeedant terpenoids (+)-norleucosceptroid A, (−)-norleucosceptroid B, and (−)-leucosceptroid K has been accomplished. This highly concise synthetic route was guided by our efforts to develop a platform for the collective synthesis of a whole family of antifeedant natural products. The synthesis features a Hauser–Kraus-type annulation followed by an unprecedented, highly efficient intramolecular dilactol aldol-type condensation reaction to produce the 5,6,5 skeleton. The developed synthetic route proceeds for norleucosceptroid A and B in 16 steps (longest linear sequence) from known compounds.

Co-reporter:Cedric L. Hugelshofer and Thomas Magauer
Organic & Biomolecular Chemistry 2017 - vol. 15(Issue 1) pp:NaN16-16
Publication Date(Web):2016/11/29
DOI:10.1039/C6OB02488B
Nature's highly efficient routes for constructing natural products have inspired chemists to mimic these processes in a laboratory setting. This Perspective presents some recent examples of conceptually different bioinspired total syntheses of complex terpenoids and thereby aims to highlight the vast benefits offered by bioinspired strategies.
Co-reporter:Adriana S. Grossmann and Thomas Magauer
Organic & Biomolecular Chemistry 2016 - vol. 14(Issue 24) pp:NaN5389-5389
Publication Date(Web):2016/01/26
DOI:10.1039/C6OB00091F
This review highlights the chemistry of trihaloethene building blocks with a special focus on commercially available 1,1,2-trichloroethene. The topics surveyed herein include the use of trihaloethenes as C2-building blocks for transition metal-catalyzed coupling reactions, addition, elimination and cycloaddition reactions as well as natural product syntheses.
Carbamic acid, N-[(chloroamino)[(methoxycarbonyl)amino]methylene]-, methyl ester
Chloro(2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl)(2'-amino-1,1'-biphenyl-2-yl)palladium(II)
Methyl 3,4-dihydro-2h-chromene-5-carboxylate
Methyl 2-chloro-3-hydroxybenzoate
Tri-tert-butylphosphine gold(I) bis(trifluoromethylsulfonyl)imide
jerantinine E
Methyl 1,2,3,4-tetrahydroquinoline-5-carboxylate