1
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Stempel ZD, Radomska HS, Coss CC, Micalizio GC. Function-Oriented Synthesis of Pentacyclic Triterpenoids and Discovery of an ent-Estrane as a Natural Product-Inspired Androgen Receptor Antagonist. Org Lett 2024; 26:3054-3059. [PMID: 38557107 DOI: 10.1021/acs.orglett.4c00697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
While pentacyclic triterpenoids have a rich history in chemistry and biology, the challenges associated with their asymmetric synthesis contribute to the current reality that medicinal exploration in the area is largely constrained to natural product derivatization. To address this deficiency, a function-oriented synthesis of pentacyclic triterpenoids was pursued. Overall, we report a divergent synthesis of 26-norgermanicol and 26-norlupeol and we have identified a new class of androgen receptor antagonist that is ∼6× more potent than lupeol.
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Affiliation(s)
- Zachary D Stempel
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Hanna S Radomska
- Division of Pharmaceutics and Pharmacology, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, United States
| | - Christopher C Coss
- Division of Pharmaceutics and Pharmacology, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, United States
| | - Glenn C Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
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2
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Reimann CE, Kim KE, Rand AW, Moghadam FA, Stoltz BM. What is a Cross-Coupling? An Argument for a Universal Definition. Tetrahedron 2023; 130:133176. [PMID: 36710952 PMCID: PMC9878734 DOI: 10.1016/j.tet.2022.133176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Despite amazing advances in cross-coupling technologies over the past several decades, there is not a consistent definition of what a cross-coupling reaction is. Often, definitions rely on comparison to "traditional" palladium-catalyzed cross-couplings pioneered in the 1970s by chemists such as Suzuki, Negishi, and Heck. While these reactions provide a basis for a cross-coupling definition, they do not define this type of transformation, originally described by Linstead almost 20 years prior. Rather than modify and compartmentalize modern transformations to categorize them into either a synthetic or mechanistic definition, we make an argument for broadening the cross-coupling definition to the union of two distinct molecular entities in a covalent-bond-forming process, to encourage discussion around exploring novel reactivity and disconnections. In addition to making a case for a universal cross-coupling definition, we cite specific examples of reactions that break the mold of prior cross-coupling definitions. We believe this perspective will stimulate dialog around what it means to be a cross-coupling and in turn inspire future developments within this field.
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Affiliation(s)
| | - Kelly E Kim
- California Institute of Technology, Pasadena, CA 91125
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3
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Wai H, Koelblen T, Hayes ME, Burris TP, Micalizio GC. Progress toward the De Novo Asymmetric Synthesis of Euphanes. Org Lett 2022; 24:3686-3690. [PMID: 35584298 DOI: 10.1021/acs.orglett.2c01299] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Progress toward an asymmetric synthesis of euphanes is described. A C14-desmethyl euphane system possessing five differentially substituted and electronically distinct alkenes has been prepared. The route employed is based on sequential metallacycle-mediated annulative cross-coupling, double asymmetric Brønsted acid mediated intramolecular Friedel-Crafts alkylation, and an oxidative rearrangement to establish the requisite C10 quaternary center. These studies have also led to the discovery of a novel euphane-based modulator of the Liver X Receptor.
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Affiliation(s)
- HtooTint Wai
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Thomas Koelblen
- University of Florida, Genetics Institute, Gainesville, Florida 32610, United States
| | - Matthew E Hayes
- University of Florida, Genetics Institute, Gainesville, Florida 32610, United States
| | - Thomas P Burris
- University of Florida, Genetics Institute, Gainesville, Florida 32610, United States
| | - Glenn C Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
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4
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Nicholson JM, Millham AB, Bucknam AR, Markham LE, Sailors XI, Micalizio GC. General Enantioselective and Stereochemically Divergent Four-Stage Approach to Fused Tetracyclic Terpenoid Systems. J Org Chem 2022; 87:3352-3362. [PMID: 35175755 PMCID: PMC9438405 DOI: 10.1021/acs.joc.1c02979] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Tetracyclic terpenoid-derived natural products are a broad class of medically relevant agents that include well-known steroid hormones and related structures, as well as more synthetically challenging congeners such as limonoids, cardenolides, lanostanes, and cucurbitanes, among others. These structurally related compound classes present synthetically disparate challenges based, in part, on the position and stereochemistry of the numerous quaternary carbon centers that are common to their tetracyclic skeletons. While de novo syntheses of such targets have been a topic of great interest for over 50 years, semisynthesis is often how synthetic variants of these natural products are explored as biologically relevant materials and how such agents are further matured as therapeutics. Here, focus was directed at establishing an efficient, stereoselective, and molecularly flexible de novo synthetic approach that could offer what semisynthetic approaches do not. In short, a unified strategy to access common molecular features of these natural product families is described that proceeds in four stages: (1) conversion of epichlorohydrin to stereodefined enynes, (2) metallacycle-mediated annulative cross-coupling to generate highly substituted hydrindanes, (3) tetracycle formation by stereoselective forging of the C9-C10 bond, and (4) group-selective oxidative rearrangement that repositions a quaternary center from C9 to C10. These studies have defined the structural features required for highly stereoselective C9-C10 bond formation and document the generality of this four-stage synthetic strategy to access a range of unique stereodefined systems, many of which bear stereochemistry/substitution/functionality not readily accessible from semisynthesis.
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Affiliation(s)
- Joshua M. Nicholson
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Adam B. Millham
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Andrea R. Bucknam
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Lauren E. Markham
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Xenia Ivanna Sailors
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Glenn C. Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
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5
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Markham L, Tolbert JD, Kull FJ, Midgett CR, Micalizio GC. An Enantiodefined Conformationally Constrained Fatty Acid Mimetic and Potent Inhibitor of ToxT. ACS Med Chem Lett 2021; 12:1493-1497. [PMID: 34531958 PMCID: PMC8436414 DOI: 10.1021/acsmedchemlett.1c00378] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 08/20/2021] [Indexed: 11/29/2022] Open
Abstract
The chiral conformation that palmitoleic acid takes when it is bound to ToxT, the master regulator of virulence genes in the bacterial pathogen Vibrio cholerae, was used as inspiration to design a novel class of fatty acid mimetics. The best mimetic, based on a chiral hydrindane, was found to be a potent inhibitor of this target. The synthetic chemistry that enabled these studies was based on the sequential use of a stereoselective annulative cross-coupling reaction and dissolving metal reduction to establish the C13 and C9 stereocenters, respectively.
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Affiliation(s)
- Lauren
E. Markham
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Jessica D. Tolbert
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - F. Jon Kull
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Charles R. Midgett
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Glenn C. Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
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6
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Shalit ZA, Valdes LC, Kim WS, Micalizio GC. From an ent-Estrane, through a nat-Androstane, to the Total Synthesis of the Marine-Derived Δ 8,9-Pregnene (+)-03219A. Org Lett 2021; 23:2248-2252. [PMID: 33635666 DOI: 10.1021/acs.orglett.1c00382] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The total synthesis of (+)-03219A, a rare Δ8,9-pregnene isolated from the marine-derived Streptomyces sp. SCSIO 03219, is described that is based on a series of transformations that enable progression from epichlorohydrin to an ent-estrane, then conversion to a nat-androstane, and finally establishment of the natural product target. Key to the success of these studies was implementation of two rearrangement processes to formally invert the quaternary center at C13 and establish the C10 quaternary center.
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Affiliation(s)
- Zachary A Shalit
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Lucas C Valdes
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Wan Shin Kim
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Glenn C Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
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7
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Zhou Z, Chen J, Chen H, Kong W. Stereoselective synthesis of pentasubstituted 1,3-dienes via Ni-catalyzed reductive coupling of unsymmetrical internal alkynes. Chem Sci 2020; 11:10204-10211. [PMID: 34094285 PMCID: PMC8162379 DOI: 10.1039/d0sc04173d] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The reductive coupling of alkynes represents a powerful strategy for the rapid synthesis of highly substituted 1,3-dienes. This method has the advantages of high atom and step economy, and readily available substrates. Unfortunately, the intermolecular coupling of unsymmetrical internal alkynes remains extremely challenging due to the difficulty in controlling self-dimerization and cross-coupling, as well as stereo- and regioselectivity. Previous reports are still limited to intramolecular processes or the use of stoichiometric amounts of metal catalyst. Herein, we report that nickel-catalyzed reductive coupling of two unsymmetrical internal alkynes can overcome the above-mentioned limitations by using a hemilabile directing group strategy to control the regioselectivity. A series of synthetically challenging penta-substituted 1,3-dienes are obtained in good yields with high regio- and enantioselectivity (mostly > 20/1 rr, >90% ee). The reductive coupling of alkynes represents a powerful strategy for the rapid synthesis of highly substituted 1,3-dienes.![]()
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Affiliation(s)
- Zhijun Zhou
- Institute for Advanced Studies (IAS), Wuhan University Wuhan Hubei 430072 P. R. China
| | - Jiachang Chen
- Institute for Advanced Studies (IAS), Wuhan University Wuhan Hubei 430072 P. R. China
| | - Herong Chen
- Institute for Advanced Studies (IAS), Wuhan University Wuhan Hubei 430072 P. R. China
| | - Wangqing Kong
- Institute for Advanced Studies (IAS), Wuhan University Wuhan Hubei 430072 P. R. China
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8
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Millham AB, Bhatt CP, Micalizio GC. From Metallacycle-Mediated Annulative Cross-Coupling to Steroidal Tetracycles through Intramolecular C9-C10 Bond Formation. Org Lett 2020; 22:6595-6599. [PMID: 32806140 DOI: 10.1021/acs.orglett.0c02358] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
While semisynthesis is a common platform for medicinal investigation of steroidal systems, varying the nature of substitution and stereochemistry at C9 and C10 remains challenging. It is demonstrated here that de novo synthesis, enabled by a metallacycle-centered annulation reaction, provides a uniquely effective means of addressing this problem. In short, double asymmetric Friedel-Crafts cyclization proved most effective for establishing anti- relative stereochemistry (with respect to C13), while an intramolecular Heck reaction reliably delivered the syn- diastereomers with high selectivity. In addition, these studies reveal that this oxidative rearrangement is effective for establishing a C10 quaternary center boasting variable alkyl or aryl substitution.
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Affiliation(s)
- Adam B Millham
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Chinmay P Bhatt
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Glenn C Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
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9
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Cai B, Panek JS. Titanium Alkoxide-Based Regioselective Alkyne-Alkyne Reductive Coupling Mediated by In Situ Generated Arylamidate. J Am Chem Soc 2020; 142:3729-3735. [PMID: 32050069 DOI: 10.1021/jacs.0c00550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Titanium alkoxide-based alkyne-alkyne reductive coupling mediated by in situ generated arylamidate is described. A high level of regioselectivity is achieved in 37 examples, where (E,E)-dienes are exclusively formed. To the best of our knowledge, this study represents the first example of an apparent amide and carbamate directing effect in metal-mediated reductive coupling.
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Affiliation(s)
- Bin Cai
- Department of Chemistry, Metcalf Center for Science and Engineering , Boston University , 590 Commonwealth Avenue , Boston , Massachusetts 02215 , United States
| | - James S Panek
- Department of Chemistry, Metcalf Center for Science and Engineering , Boston University , 590 Commonwealth Avenue , Boston , Massachusetts 02215 , United States
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10
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Manßen M, Schafer LL. Titanium catalysis for the synthesis of fine chemicals – development and trends. Chem Soc Rev 2020; 49:6947-6994. [DOI: 10.1039/d0cs00229a] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Atlas as a Titan(ium) is holding the earth-abundant chemistry world. Titanium is the second most abundant transition metal, is a key player in important industrial processes (e.g. polyethylene) and shows much promise for diverse applications in the future.
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Affiliation(s)
- Manfred Manßen
- The Department of Chemistry
- The University of British Columbia
- Vancouver
- Canada
| | - Laurel L. Schafer
- The Department of Chemistry
- The University of British Columbia
- Vancouver
- Canada
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11
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Kim WS, Shalit ZA, Nguyen SM, Schoepke E, Eastman A, Burris TP, Gaur AB, Micalizio GC. A synthesis strategy for tetracyclic terpenoids leads to agonists of ERβ. Nat Commun 2019; 10:2448. [PMID: 31164645 PMCID: PMC6547701 DOI: 10.1038/s41467-019-10415-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 05/08/2019] [Indexed: 02/07/2023] Open
Abstract
Natural product and natural product-like molecules continue to be important for the development of pharmaceutical agents, as molecules in this class play a vital role in the pipeline for new therapeutics. Among these, tetracyclic terpenoids are privileged, with >100 being FDA-approved drugs. Despite this significant pharmaceutical success, there remain considerable limitations to broad medicinal exploitation of the class due to lingering scientific challenges associated with compound availability. Here, we report a concise asymmetric route to forging natural and unnatural (enantiomeric) C19 and C20 tetracyclic terpenoid skeletons suitable to drive medicinal exploration. While efforts have been focused on establishing the chemical science, early investigations reveal that the emerging chemical technology can deliver compositions of matter that are potent and selective agonists of the estrogen receptor beta, and that are selectively cytotoxic in two different glioblastoma cell lines (U251 and U87). Many natural-product like drugs have a tetracyclic terpenoid core. Here, the authors developed a synthesis of triterpene-like tetracyclic systems, and apply this method to the preparation of a number of enantiomeric compounds, two of which are very selective ligands for estrogen receptor beta
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Affiliation(s)
- Wan Shin Kim
- Dartmouth College, Department of Chemistry, Burke Laboratory, Hanover, NH, 03755, USA
| | - Zachary A Shalit
- Dartmouth College, Department of Chemistry, Burke Laboratory, Hanover, NH, 03755, USA
| | - Sidney M Nguyen
- Dartmouth College, Geisel School of Medicine, Department of Neurology, Lebanon, NH, 03756, USA
| | - Emmalie Schoepke
- Center for Clinical Pharmacology, Washington University School of Medicine and St. Louis College of Pharmacy, St. Louis, MO, 63110, USA
| | - Alan Eastman
- Dartmouth College, Geisel School of Medicine, Department of Molecular and Systems Biology, Lebanon, NH, 03756, USA
| | - Thomas P Burris
- Center for Clinical Pharmacology, Washington University School of Medicine and St. Louis College of Pharmacy, St. Louis, MO, 63110, USA
| | - Arti B Gaur
- Dartmouth College, Geisel School of Medicine, Department of Neurology, Lebanon, NH, 03756, USA.
| | - Glenn C Micalizio
- Dartmouth College, Department of Chemistry, Burke Laboratory, Hanover, NH, 03755, USA.
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12
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Leon RM, Ravi D, An JS, del Genio CL, Rheingold AL, Gaur AB, Micalizio GC. Synthesis of C14-Desmethylene Corialactone D and Discovery of Inhibitors of Nerve Growth Factor Mediated Neurite Outgrowth. Org Lett 2019; 21:3193-3197. [PMID: 30995050 PMCID: PMC8420866 DOI: 10.1021/acs.orglett.9b00921] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
An asymmetric synthesis of C14-desmethylene corialactone D is described on the basis of strategic application of a metallacycle-mediated annulative cross-coupling reaction, a Still [2,3]-Wittig rearrangement, and Morken's hydroxyl-directed diboration reaction. While representing a convenient approach to access novel compositions of matter inspired by the sesquiterpenoid natural product class (including classic natural product synthesis targets including the picrotaxanes and dendrobine), these studies have led to the discovery of natural product-inspired agents that inhibit nerve growth factor (NGF)-mediated neurite outgrowth in PC-12 cells.
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Affiliation(s)
- Robert M. Leon
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Divya Ravi
- Dartmouth College, Geisel School of Medicine, Lebanon, New Hampshire 03756, United States
| | - Jennifer S. An
- Dartmouth College, Geisel School of Medicine, Lebanon, New Hampshire 03756, United States
| | - Carmen L. del Genio
- Dartmouth College, Geisel School of Medicine, Lebanon, New Hampshire 03756, United States
| | - Arnold L. Rheingold
- Department of Chemistry, University of California—San Diego, La Jolla, California 92093, United States
| | - Arti B. Gaur
- Dartmouth College, Geisel School of Medicine, Lebanon, New Hampshire 03756, United States
| | - Glenn C. Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
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13
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Beaumier EP, Pearce AJ, See XY, Tonks IA. Modern applications of low-valent early transition metals in synthesis and catalysis. Nat Rev Chem 2019; 3:15-34. [PMID: 30989127 PMCID: PMC6462221 DOI: 10.1038/s41570-018-0059-x] [Citation(s) in RCA: 132] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Low-valent early transition metals are often intrinsically highly reactive as a result of their strong propensity toward oxidation to more stable high-valent states. Harnessing these highly reducing complexes for productive reactivity is potentially powerful for C-C bond construction, organic reductions, small-molecule activation and many other reactions that offer orthogonal chemoselectivity and/or regioselectivity patterns to processes promoted by late transition metals. Recent years have seen many exciting new applications of low-valent metals through building new catalytic and/or multicomponent reaction manifolds out of classical reactivity patterns. In this Review, we survey new methods that employ early transition metals and invoke low-valent precursors or intermediates in order to identify common themes and strategies in synthesis and catalysis.
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Affiliation(s)
- Evan P. Beaumier
- Department of Chemistry, University of Minnesota, Minneapolis, MN, USA
| | - Adam J. Pearce
- Department of Chemistry, University of Minnesota, Minneapolis, MN, USA
| | - Xin Yi See
- Department of Chemistry, University of Minnesota, Minneapolis, MN, USA
| | - Ian A. Tonks
- Department of Chemistry, University of Minnesota, Minneapolis, MN, USA
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14
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Condakes ML, Novaes LFT, Maimone TJ. Contemporary Synthetic Strategies toward seco-Prezizaane Sesquiterpenes from Illicium Species. J Org Chem 2018; 83:14843-14852. [PMID: 30525614 PMCID: PMC6467809 DOI: 10.1021/acs.joc.8b02802] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Since the elucidation of the structure of anisatin in the late 1960s, sesquiterpene lactones from various Illicium species of plants have captivated synthetic chemists worldwide, resulting in a large body of synthetic work. In particular, Illicium sesquiterpenes containing the seco-prezizaane carbon framework have seen immense interest in recent years owing to desirable structural and medicinal attributes. This synopsis will focus on recently developed synthetic strategies to access these compact, highly oxidized terpenoids.
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Affiliation(s)
- Matthew L. Condakes
- Department of Chemistry, University of California–Berkeley, Berkeley, CA, 94720
| | - Luiz F. T. Novaes
- Department of Chemistry, University of California–Berkeley, Berkeley, CA, 94720
| | - Thomas J. Maimone
- Department of Chemistry, University of California–Berkeley, Berkeley, CA, 94720
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15
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Nagasawa S, Sasano Y, Iwabuchi Y. Synthesis of 1,3-Cycloalkadienes from Cycloalkenes: Unprecedented Reactivity of Oxoammonium Salts. Angew Chem Int Ed Engl 2018; 55:13189-13194. [PMID: 27650040 DOI: 10.1002/anie.201607752] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Indexed: 01/14/2023]
Abstract
Few methods allow for the direct conversion of cycloalkenes into cycloalkadienes with high chemo- and regioselectivity. Herein, we report a convenient one-pot process for this transformation that involves the unprecedented N-preferential group transfer of N-oxoammonium salts to cycloalkenes, followed by Cope elimination, to afford cycloalkadienes at room temperature and pressure.
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Affiliation(s)
- Shota Nagasawa
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Yusuke Sasano
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Yoshiharu Iwabuchi
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan.
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16
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Shalit ZA, Micalizio GC. A Highly Chemo-, Regio-, and Stereoselective Metallacycle-Mediated Annulation Between a Conjugated Enyne and an Ene-Diyne. ARKIVOC 2018; 2018:132-138. [PMID: 31742254 DOI: 10.24820/ark.5550190.p010.487] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Alkoxide-directed metal-centered intermolecular [2+2+2] annulation is shown to chemo-, regio-, and stereoselectively engage two polyunsaturated substrate in productive cyclization chemistry. This annulation process is unique in the field, revealing that it is possible to selectively engage three of five π-systems residing in the coupling partners in initial [2+2+2] reaction, and demonstrating that one of the two remaining π-systems (the TMS-alkyne) can ultimately serve to simply generate a new metallacyclopentene of great potential value in additional metallacycle-mediated coupling chemistry.
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Affiliation(s)
- Zachary A Shalit
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, NH 03755
| | - Glenn C Micalizio
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, NH 03755
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17
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Micalizio GC, Mizoguchi H. The Development of Alkoxide-Directed Metallacycle-Mediated Annulative Cross-Coupling Chemistry. Isr J Chem 2017; 57:228-238. [PMID: 28652644 PMCID: PMC5482546 DOI: 10.1002/ijch.201600098] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Alkoxide-directed metallacycle-mediated cross-coupling is a rapidly growing area of reaction methodology in organic chemistry. Over the last decade, developments have resulted in > thirty new and highly selective intermolecular (or "convergent") C-C bond-forming reactions that have established powerful retrosynthetic relationships in stereoselective synthesis. While early studies were focused on developing transformations that forge a single C-C bond by way of a functionalized and unsaturated metallacyclopentane intermediate, recent advances mark the ability to employ this organometallic intermediate in additional stereoselective transformations. Among these more advanced coupling processes, those that embrace the metallacycle in subsequent [4+2] chemistry have resulted in the realization of a number of highly selective annulative cross-coupling reactions that deliver densely functionalized and angularly substituted carbocycles. This review discusses the early development of this chemistry, recent advances in reaction methodology, and shares a glimpse of the power of these processes in natural product synthesis.
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18
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Sun Z, Hu S, Huo Y, Wang Z. Titanium tetrachloride-mediated synthesis of N-aryl-substituted azacycles from cyclic ethers. RSC Adv 2017. [DOI: 10.1039/c6ra27325d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Five- and six-membered N-aryl-substituted azacycles were synthesized from amines and cyclic ethers under mild conditions while no expensive metal reagent was required.
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Affiliation(s)
- Zunming Sun
- State Key Laboratory and Institute of Elemento-Organic Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Shanshan Hu
- State Key Laboratory and Institute of Elemento-Organic Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Yan Huo
- State Key Laboratory and Institute of Elemento-Organic Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
| | - Zhihong Wang
- State Key Laboratory and Institute of Elemento-Organic Chemistry
- Nankai University
- Tianjin 300071
- P. R. China
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19
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O'Rourke NF, Kier MJ, Micalizio GC. Metallacycle-Mediated Cross-Coupling in Natural Product Synthesis. Tetrahedron 2016; 72:7093-7123. [PMID: 27765997 PMCID: PMC5067085 DOI: 10.1016/j.tet.2016.08.053] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Natasha F O'Rourke
- Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States
| | - Matthew J Kier
- Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States
| | - Glenn C Micalizio
- Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States
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20
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Mizoguchi H, Micalizio GC. Synthesis of Angularly Substituted trans-Fused Decalins through a Metallacycle-Mediated Annulative Cross-Coupling Cascade. Angew Chem Int Ed Engl 2016; 55:13099-13103. [PMID: 27634059 PMCID: PMC5056368 DOI: 10.1002/anie.201606962] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Indexed: 01/07/2023]
Abstract
A convergent coupling reaction is described that enables the stereoselective construction of angularly substituted trans-fused decalins from acyclic precursors. The process builds on our alkoxide-directed titanium-mediated alkyne-alkyne coupling and employs a 1,7-enyne coupling partner. Overall, the reaction is thought to proceed through initial formation of a tetrasusbstituted metallacyclopentadiene, stereoselective intramolecular [4+2] cycloaddition, elimination, isomerization, and regio- and stereoselective protonation. Distinct from our early studies directed at the synthesis of trans-fused hydrindanes, the current annulative coupling reveals an important effect of TMSCl in controlling the final protonation-the event that establishes the stereochemistry of the ring fusion.
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Affiliation(s)
- Haruki Mizoguchi
- Department of Chemistry, Dartmouth College, 6128 Burke Laboratory, Hanover, NH, 03755, USA
| | - Glenn C Micalizio
- Department of Chemistry, Dartmouth College, 6128 Burke Laboratory, Hanover, NH, 03755, USA.
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21
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Mizoguchi H, Micalizio GC. Synthesis of Angularly Substituted trans
-Fused Decalins through a Metallacycle-Mediated Annulative Cross-Coupling Cascade. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201606962] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Haruki Mizoguchi
- Department of Chemistry; Dartmouth College; 6128 Burke Laboratory Hanover NH 03755 USA
| | - Glenn C. Micalizio
- Department of Chemistry; Dartmouth College; 6128 Burke Laboratory Hanover NH 03755 USA
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22
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Nagasawa S, Sasano Y, Iwabuchi Y. Synthesis of 1,3-Cycloalkadienes from Cycloalkenes: Unprecedented Reactivity of Oxoammonium Salts. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201607752] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Shota Nagasawa
- Department of Organic Chemistry; Graduate School of Pharmaceutical Sciences; Tohoku University; 6-3 Aoba, Aramaki, Aoba-ku Sendai 980-8578 Japan
| | - Yusuke Sasano
- Department of Organic Chemistry; Graduate School of Pharmaceutical Sciences; Tohoku University; 6-3 Aoba, Aramaki, Aoba-ku Sendai 980-8578 Japan
| | - Yoshiharu Iwabuchi
- Department of Organic Chemistry; Graduate School of Pharmaceutical Sciences; Tohoku University; 6-3 Aoba, Aramaki, Aoba-ku Sendai 980-8578 Japan
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23
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Cassidy JS, Mizoguchi H, Micalizio GC. Acceleration of metallacycle-mediated alkyne-alkyne cross-coupling with TMSCl. Tetrahedron Lett 2016; 57:3848-3850. [PMID: 27713588 DOI: 10.1016/j.tetlet.2016.07.045] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Investigation of titanium-centered metallacycle-mediated cross-coupling between unsymmetrical internal alkynes has led to the discovery that TMSCl significantly accelerates the C-C bond forming event. We report a collection of results that compare the efficiency of this reaction employing Ti(Oi-Pr)4/2n-BuLi in PhMe with and without TMSCl, demonstrating in every case that the presence of TMSCl has a profound impact on efficiency. While relevant in the context of developing this fundamental bond-forming process as an entry to more complex organometallic transformations, these modified reaction conditions allow coupling processes to be run at > 10 times the concentrations previously possible [in 2.4M n-BuLi (hexanes)], without the requirement of additional solvent. Finally, we demonstrate the effectiveness of these modified reaction conditions for the annulative cross-coupling between TMS-alkynes and 1,6-enynes leading to the formation of angularly substituted hydrindanes with, now well appreciated, high levels of regio- and stereoselection.
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Affiliation(s)
- James S Cassidy
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, NH 03755
| | - Haruki Mizoguchi
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, NH 03755
| | - Glenn C Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, NH 03755
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24
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Aquino C, Greszler SN, Micalizio GC. Synthesis of the Cortistatin Pentacyclic Core by Alkoxide-Directed Metallacycle-Mediated Annulative Cross-Coupling. Org Lett 2016; 18:2624-7. [PMID: 27193994 PMCID: PMC4892975 DOI: 10.1021/acs.orglett.6b01048] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The pentacyclic core skeleton of the cortistatins has been prepared in a stereoselective fashion by strategic use of an alkoxide-directed metallacycle-mediated annulative cross-coupling. This metal-centered tandem reaction delivers a polyunsaturated hydrindane and establishes the C13 stereodefined quaternary center with high levels of stereocontrol. Subsequent regio- and stereoselective global hydroboration results in the realization of the DE-trans ring fusion and a tertiary alcohol at C8. Establishment of the ABC-tricyclic subunit was then accomplished through phenolic oxidation/trans-acetalization, chemoselective reduction, regioselective cleavage, and intramolecular alkylation at C5.
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Affiliation(s)
- Claudio Aquino
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, NH 03755
- Department of Chemistry, The Scripps Research Institute, Jupiter, FL 33458
| | | | - Glenn C. Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, NH 03755
- Department of Chemistry, The Scripps Research Institute, Jupiter, FL 33458
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25
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Cheng X, Micalizio GC. Synthesis of Neurotrophic Seco-prezizaane Sesquiterpenes (1R,10S)-2-Oxo-3,4-dehydroneomajucin, (2S)-Hydroxy-3,4-dehydroneomajucin, and (-)-Jiadifenin. J Am Chem Soc 2016; 138:1150-3. [PMID: 26785051 PMCID: PMC4879688 DOI: 10.1021/jacs.5b12694] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An asymmetric approach to the synthesis of neurotrophic seco-prezizaane sesquiterpenes is described that is based on the strategic application of a hydroxyl-directed metallacycle-mediated [2 + 2 + 2] annulation and an intramolecular radical cyclization cascade. Targets prepared are among the most potent members of the natural product class and include (1R,10S)-2-oxo-3,4-dehydroneomajucin, (2S)-hydroxy-3,4-dehydroneomajucin, and (-)-jiadifenin. In addition to representing the first application of the alkoxide-directed metallacycle-mediated hydrindane-forming annulation reaction in natural product synthesis and the first total synthesis of (2S)-hydroxy-3,4-dehydroneomajucin, these pursuits have resulted in the elucidation of a complex radical cascade process for installation of the C5 quaternary center common to the natural product class.
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Affiliation(s)
- Xiayun Cheng
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, NH 03755
| | - Glenn C. Micalizio
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, NH 03755
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26
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Kim WS, Aquino C, Mizoguchi H, Micalizio GC. LiOO t-Bu as a terminal oxidant in a titanium alkoxide-mediated [2+2+2] reaction cascade. Tetrahedron Lett 2015; 56:3357-3359. [PMID: 26097265 DOI: 10.1016/j.tetlet.2015.01.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
LiOOt-Bu is an effective oxidant for converting the penultimate organometallic intermediate generated in a titanium alkoxide-mediated [2+2+2] reaction cascade to an allylic alcohol. Oxidation of the presumed allylic titanium species is highly regioselective, providing direct access to substituted hydroindanes containing a primary allylic alcohol. In addition to demonstrating the feasibility of this oxidation process, we document the ability to convert the primary allylic alcohol products to angularly substituted cis-fused hydroindanes.
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Affiliation(s)
- Wan Shin Kim
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, NH 03755, USA
| | - Claudio Aquino
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, NH 03755, USA
| | - Haruki Mizoguchi
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, NH 03755, USA
| | - Glenn C Micalizio
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, NH 03755, USA
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27
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Mizoguchi H, Micalizio GC. Synthesis of Highly Functionalized Decalins via Metallacycle-Mediated Cross-Coupling. J Am Chem Soc 2015; 137:6624-8. [PMID: 25930967 DOI: 10.1021/jacs.5b02107] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Bridged bicyclic metallacyclopentenes generated from the [4 + 2] cycloaddition of metallacyclopentadienes with alkenes have been proposed as reactive intermediates in the course of [2 + 2 + 2] annulation reactions. Recently a collection of alkoxide-directed Ti-mediated [2 + 2 + 2] annulation reactions have been discovered for the synthesis of densely functionalized hydrindanes, where the bridged bicyclic metallacyclopentenes from intramolecular [4 + 2] were treated as fleeting intermediates en route to cyclohexadiene products formed by formal cheletropic extrusion of Ti(Oi-Pr)2. In studies aimed at understanding the course of these organometallic cascade reactions it was later discovered that these bridged bicyclic intermediates can be trapped by various elimination processes. Here, we have realized metallacycle-mediated annulation reactions for the assembly of angularly substituted decalins--structural motifs that are ubiquitous in natural products and molecules of pharmaceutical relevance. In addition to defining the basic annulation reaction we have discovered a surprising stability associated with the complex organometallic intermediates generated in the course of this coupling process and document here the ability to control the fate of such species. Ligand-induced cheletropic extrusion of the titanium center delivers cyclohexadiene-containing products, while several distinct protonation events have been identified to realize polycyclic products that contain three new stereocenters (one of which is the angular quaternary center that is a hallmark of alkoxide-directed titanium-mediated [2 + 2 + 2] annulation reactions). Examples of this metallacycle-mediated annulation reaction are provided to demonstrate that a range of stereodefined fused bicyclo[4.4.0]decanes are accessible, including those that contain aromatic and aliphatic substituents, and an empirical model is presented to accompany the observations made.
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Affiliation(s)
- Haruki Mizoguchi
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Glenn C Micalizio
- Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, New Hampshire 03755, United States
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28
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Micalizio GC, Hale SB. Reaction design, discovery, and development as a foundation to function-oriented synthesis. Acc Chem Res 2015; 48:663-73. [PMID: 25668752 DOI: 10.1021/ar500408e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Convergent C-C bond-forming reactions define the fabric of organic synthesis and, when applied in complex molecule synthesis, can have a profound impact on efficiency by decreasing the longest linear sequence of transformations required to convert simple starting materials to complex targets. Despite their well-appreciated strategic significance, campaigns in natural product synthesis typically embrace only a small suite of reactivity to achieve such bond construction (i.e., nucleophilic addition to polarized π-bonds, nucleophilic substitution, cycloaddition, and metal-catalyzed "cross-coupling"), therefore limiting the sites at which convergent coupling chemistry can be strategically employed. In our opinion, it is far too often that triumphs in the field are defined by chemical sequences that do not address the challenges associated with discovery, development, and production of natural product-inspired agents. We speculated that advancing an area of chemical reactivity not represented in the few well-established strategies for convergent C-C bond formation may lead to powerful new retrosynthetic relationships that could simplify approaches to the syntheses of a variety of different classes of natural products. Our studies ultimately embraced the pursuit of strategies to control the course of metallacycle-mediated "cross-coupling" between substrates containing sites of simple π-unsaturation (ubiquitous functionality in organic chemistry including alkenes, alkynes, allenes, aldehydes, and imines, among others). In just eight years since our initial publication in this area, we have defined over 20 stereoselective intermolecular C-C bond-forming reactions that provide access to structural motifs of relevance for the synthesis of polyketides, fatty acids, alkaloids, and terpenes, while doing so in a direct and stereoselective fashion. These achievements continue to serve as the foundation of my group's activity in natural product and function-oriented synthesis, where our achievements in reaction development are challenged in the context of complex targets. Among our early efforts, we achieved the most concise synthesis of a benzoquinone ansamycin ever described (macbecin I), and moved beyond this achievement to explore the role of our chemistry in function-oriented synthesis targeting the discovery of natural product-inspired Hsp90 inhibitors. These later efforts have led to the discovery of a uniquely selective benzoquinone ansamycin-inspired Hsp90 inhibitor that lacks the problematic quinone present in the natural series. This achievement was made possible by a concise chemical synthesis pathway that had at its core the application of metallacycle-mediated cross-coupling chemistry.
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Affiliation(s)
- Glenn C. Micalizio
- Department of Chemistry,
Burke Laboratory, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Sarah B. Hale
- Department of Chemistry,
Burke Laboratory, Dartmouth College, Hanover, New Hampshire 03755, United States
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29
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30
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Cheng X, Micalizio GC. An annulation reaction for the synthesis of cross-conjugated triene-containing hydroindanes from acyclic precursors. Org Lett 2014; 16:5144-7. [PMID: 25216381 PMCID: PMC4184447 DOI: 10.1021/ol502496d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2014] [Indexed: 01/05/2023]
Abstract
In efforts directed toward the synthesis of seco-prezizaane sesquiterpenoids, a stereoselective annulation reaction has been developed between 4-hydroxy-1,6-enynes and TMS-alkynes that delivers cross-conjugated triene-containing hydroindanes. Contrary to previous reports, enyne substrates bearing two propargylic ethers enable the presumed organometallic intermediate to be trapped by double elimination. The tendency of products from this annulation to undergo Diels-Alder-based dimerization was harnessed to accomplish a two-step complexity-generating sequence en route to densely functionalized carbo- and heteorocyclic systems.
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Affiliation(s)
- Xiayun Cheng
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
| | - Glenn C. Micalizio
- Department of Chemistry, Dartmouth College, Burke Laboratory, Hanover, New Hampshire 03755, United States
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31
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Jeso V, Aquino C, Cheng X, Mizoguchi H, Nakashige M, Micalizio GC. Synthesis of angularly substituted trans-fused hydroindanes by convergent coupling of acyclic precursors. J Am Chem Soc 2014; 136:8209-12. [PMID: 24856045 PMCID: PMC4063191 DOI: 10.1021/ja504374j] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
![]()
Angularly substituted
trans-fused hydroindanes are now accessible
by the direct and convergent union of trimethylsilyl (TMS)-alkynes
with 4-hydroxy-1,6-enynes by a process that forges three C–C
bonds, one C–H bond, and two new stereocenters. The annulation
is proposed to proceed by initial formation of a Ti–alkyne
complex (with a TMS-alkyne) followed by regioselective alkoxide-directed
coupling with the enyne, stereoselective intramolecular cycloaddition,
elimination of phenoxide, 1,3-metallotropic shift, and stereoselective
protonation of the penultimate allylic organometallic intermediate.
Several examples are given to demonstrate the compatibility of this
reaction with substrates bearing aromatic and aliphatic substituents,
and an empirical model is presented to accompany the stereochemical
observations.
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Affiliation(s)
- Valer Jeso
- Department of Chemistry, Burke Laboratory, Dartmouth College , Hanover, New Hampshire 03755, United States
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32
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You X, Xie X, Sun R, Chen H, Li S, Liu Y. Titanium-mediated cross-coupling reactions of 1,3-butadiynes with α-iminonitriles to 3-aminopyrroles: observation of an imino aza-Nazarov cyclization. Org Chem Front 2014. [DOI: 10.1039/c4qo00159a] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ti(OiPr)4/2 nBuLi-mediated highly efficient cross-coupling reactions of 1,3-butadiynes with α-iminonitriles are described, which provide convenient access to functionalized 3-aminopyrroles.
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Affiliation(s)
- Xu You
- State Key Laboratory of Organometallic Chemistry
- Shanghai Institute of Organic Chemistry
- Chinese Academy of Sciences
- Shanghai 200032, People's Republic of China
| | - Xin Xie
- State Key Laboratory of Organometallic Chemistry
- Shanghai Institute of Organic Chemistry
- Chinese Academy of Sciences
- Shanghai 200032, People's Republic of China
| | - Renhong Sun
- State Key Laboratory of Organometallic Chemistry
- Shanghai Institute of Organic Chemistry
- Chinese Academy of Sciences
- Shanghai 200032, People's Republic of China
| | - Haoyi Chen
- State Key Laboratory of Organometallic Chemistry
- Shanghai Institute of Organic Chemistry
- Chinese Academy of Sciences
- Shanghai 200032, People's Republic of China
| | - Shi Li
- State Key Laboratory of Organometallic Chemistry
- Shanghai Institute of Organic Chemistry
- Chinese Academy of Sciences
- Shanghai 200032, People's Republic of China
| | - Yuanhong Liu
- State Key Laboratory of Organometallic Chemistry
- Shanghai Institute of Organic Chemistry
- Chinese Academy of Sciences
- Shanghai 200032, People's Republic of China
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