1
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Thorpe MP, Blackwell DJ, Knollmann BC, Johnston JN. Backbone-Determined Antiarrhythmic Structure-Activity Relationships for a Mirror Image, Oligomeric Depsipeptide Natural Product. J Med Chem 2024. [PMID: 38958200 DOI: 10.1021/acs.jmedchem.4c00923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
Cyclic oligomeric depsipeptides (COD) are a structural class within naturally occurring compounds with a wide range of biological activity. Verticilide is a COD (24-membered ring) that was identified by its inhibition of insect ryanodine receptor (RyR). We have since found that the enantiomer of verticilide (ent-verticilide, 1) is a potent inhibitor of mammalian RyR2, a cardiac calcium channel, and therefore a potential antiarrhythmic agent. Oddly, nat-verticilide does not inhibit RyR2. To further develop ent-verticilide as an antiarrhythmic, we explored potential SAR through systematic modification of the ester's functionality to both N-H and N-Me amides. The syntheses of these ent-verticilide-inspired analogs are detailed using a monomer-based platform enabled by enantioselective catalysis. Two analogs among 23 exhibited measurable reduction of calcium sparks in a functional assay of RyR2 activity. These findings illustrate the value of natural product-inspired therapeutic development, but the less-studied approach where the non-natural enantiomeric series harbors important SAR.
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Affiliation(s)
- Madelaine P Thorpe
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Daniel J Blackwell
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37235, United States
| | - Bjorn C Knollmann
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37235, United States
| | - Jeffrey N Johnston
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
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2
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Šeflová J, Schwarz JA, Smith AN, Svensson B, Blackwell DJ, Phillips TA, Nikolaienko R, Bovo E, Rebbeck RT, Zima AV, Thomas DD, Van Petegem F, Knollmann BC, Johnston JN, Robia SL, Cornea RL. RyR2 Binding of an Antiarrhythmic Cyclic Depsipeptide Mapped Using Confocal Fluorescence Lifetime Detection of FRET. ACS Chem Biol 2023; 18:2290-2299. [PMID: 37769131 DOI: 10.1021/acschembio.3c00376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2023]
Abstract
Hyperactivity of cardiac sarcoplasmic reticulum (SR) ryanodine receptor (RyR2) Ca2+-release channels contributes to heart failure and arrhythmias. Reducing the RyR2 activity, particularly during cardiac relaxation (diastole), is a desirable therapeutic goal. We previously reported that the unnatural enantiomer (ent) of an insect-RyR activator, verticilide, inhibits porcine and mouse RyR2 at diastolic (nanomolar) Ca2+ and has in vivo efficacy against atrial and ventricular arrhythmia. To determine the ent-verticilide structural mode of action on RyR2 and guide its further development via medicinal chemistry structure-activity relationship studies, here, we used fluorescence lifetime (FLT)-measurements of Förster resonance energy transfer (FRET) in HEK293 cells expressing human RyR2. For these studies, we used an RyR-specific FRET molecular-toolkit and computational methods for trilateration (i.e., using distances to locate a point of interest). Multiexponential analysis of FLT-FRET measurements between four donor-labeled FKBP12.6 variants and acceptor-labeled ent-verticilide yielded distance relationships placing the acceptor probe at two candidate loci within the RyR2 cryo-EM map. One locus is within the Ry12 domain (at the corner periphery of the RyR2 tetrameric complex). The other locus is sandwiched at the interface between helical domain 1 and the SPRY3 domain. These findings document RyR2-target engagement by ent-verticilide, reveal new insight into the mechanism of action of this new class of RyR2-targeting drug candidate, and can serve as input in future computational determinations of the ent-verticilide binding site on RyR2 that will inform structure-activity studies for lead optimization.
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Affiliation(s)
- Jaroslava Šeflová
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois 60153, United States
| | - Jacob A Schwarz
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Abigail N Smith
- Department of Chemistry & Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Bengt Svensson
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Daniel J Blackwell
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232, United States
| | - Taylor A Phillips
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois 60153, United States
| | - Roman Nikolaienko
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois 60153, United States
| | - Elisa Bovo
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois 60153, United States
| | - Robyn T Rebbeck
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Aleksey V Zima
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois 60153, United States
| | - David D Thomas
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Centre, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Björn C Knollmann
- Department of Chemistry & Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Jeffrey N Johnston
- Department of Chemistry & Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Seth L Robia
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois 60153, United States
| | - Răzvan L Cornea
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
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3
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Paquette AR, Boddy CN. Macrocyclization strategies for the total synthesis of cyclic depsipeptides. Org Biomol Chem 2023; 21:8043-8053. [PMID: 37750186 DOI: 10.1039/d3ob01229h] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Cyclic depsipeptides are an important class of peptide natural products that are defined by the presence of ester and amide bonds within the macrocycle. The structural diversity of depsipeptides has required the development of a broad range of synthetic strategies to access these biologically active compounds. Solid phase peptide synthesis (SPPS) strategies have been an invaluable tool in their synthesis. The key aspect of their synthesis is the macrocyclization strategy. Three main strategies are used, solution phase macrolactamization of acyclic ester containing peptide, on-resin macrolactamization of a sidechain-anchored peptide, and the solution phase macrolactonization of a linear peptide. Additionally, biocatalysts have been used to produce these compounds in a regio- and chemo-selective manner. Each compound offers unique challenges, requiring careful synthetic design to avoid undesirable side reactivity or unwanted epimerization during the esterification and macrocyclizing steps. This focused review analyzes these three strategies for cyclic depsipeptide natural product total synthesis with selected examples from the literature between 2001-2023.
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Affiliation(s)
- André R Paquette
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, K1N 6N5, Canada.
| | - Christopher N Boddy
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, K1N 6N5, Canada.
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4
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Smith A, Thorpe MP, Blackwell DJ, Batiste SM, Hopkins CR, Schley ND, Knollmann BC, Johnston JN. Structure-Activity Relationships for the N-Me- Versus N-H-Amide Modification to Macrocyclic ent-Verticilide Antiarrhythmics. ACS Med Chem Lett 2022; 13:1755-1762. [PMID: 36385927 PMCID: PMC9661706 DOI: 10.1021/acsmedchemlett.2c00377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 09/29/2022] [Indexed: 11/28/2022] Open
Abstract
The synthesis of all N-Me and N-H analogues of ent-verticilide is described, enabling a structure-activity relationship study based on cardiac ryanodine receptor (RyR2) calcium ion channel inhibition. The use of permeabilized cardiomyocytes allowed us to correlate the degree of N-methylation with activity without concern for changes in passive membrane permeability that these modifications can cause. A key hypothesis was that the minimal pharmacophore may be repeated in this cyclic oligomeric octadepsipeptide (a 24-membered macrocycle), opening the possibility that target engagement will not necessarily be lost with a single N-Me → N-H modification. The effect in the corresponding 18-membered ring oligomer (ent-verticilide B1) was also investigated. We report here that a high degree of N-methyl amide content is critical for activity in the ent-verticilide series but not entirely so for the ent-verticilide B1 series.
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Affiliation(s)
- Abigail
N. Smith
- Department
of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville 37235, Tennessee, United States
| | - Madelaine P. Thorpe
- Department
of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville 37235, Tennessee, United States
| | - Daniel J. Blackwell
- Department
of Medicine, Vanderbilt University Medical
Center, Nashville 37235, Tennessee, United States
| | - Suzanne M. Batiste
- Department
of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville 37235, Tennessee, United States
| | - Corey R. Hopkins
- Department
of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha 68198, Nebraska, United States
| | - Nathan D. Schley
- Department
of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville 37235, Tennessee, United States
| | - Bjorn C. Knollmann
- Department
of Medicine, Vanderbilt University Medical
Center, Nashville 37235, Tennessee, United States
| | - Jeffrey N. Johnston
- Department
of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville 37235, Tennessee, United States
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5
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Crocker MS, Deng Z, Johnston JN. Preparation of N-Aryl Amides by Epimerization-Free Umpolung Amide Synthesis. J Am Chem Soc 2022; 144:16708-16714. [PMID: 36067492 PMCID: PMC9634722 DOI: 10.1021/jacs.2c05986] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Amide synthesis is one of the most widely practiced chemical reactions, owing to its use in drug development and peptide synthesis. Despite the importance of these applications, the attendant effort to eliminate waste associated with these protocols has met with limited success, and pernicious α-epimerization is most often minimized but not eliminated when targeting challenging amides (e.g., N-aryl amides). This effort has focused on what is essentially a single paradigm in amide formation wherein an electrophilic acyl donor reacts with a nucleophilic amine. Umpolung amide synthesis (UmAS) emerged from α-halo nitroalkane reactions with amines and has since been developed into a method for the synthesis of enantiopure amides using entirely catalytic, enantioselective synthesis. However, its inability to forge N-aryl amides has been a longstanding problem, one limiting its application more broadly in drug development where α-chiral N-aryl amides are increasingly common. We report here the reaction of α-fluoronitroalkanes and N-aryl hydroxyl amines for the direct synthesis of N-aryl amides using a simple Brønsted base as the promoter. No other activating agents are required, and experiments guided by mechanistic hypotheses outline a mechanism based on the UmAS paradigm and confirm that the N-aryl amide, not the N-aryl hydroxamic acid, is the direct product. Ultimately, select chiral α-amino-N-aryl amides were prepared with complete conservation of enantioenrichment, in contrast to a parallel demonstration of their ability to epimerize using the conventional amide synthesis alternative.
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Affiliation(s)
- Michael S. Crocker
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Zihang Deng
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Jeffrey N. Johnston
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, USA
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6
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Smith AN, Blackwell DJ, Knollmann BC, Johnston JN. Ring Size as an Independent Variable in Cyclooligomeric Depsipeptide Antiarrhythmic Activity. ACS Med Chem Lett 2021; 12:1942-1947. [PMID: 34917258 DOI: 10.1021/acsmedchemlett.1c00508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 11/19/2021] [Indexed: 12/12/2022] Open
Abstract
Hit-to-lead studies employ a variety of strategies to optimize binding to a target of interest. When a structure for the target is available, hypothesis-driven structure-activity relationships (SAR) are a powerful strategy for refining the pharmacophore to achieve robust binding and selectivity characteristics necessary to identify a lead compound. Recrafting the three-dimensional space occupied by a small molecule, optimization of hydrogen bond contacts, and enhancing local attractive interactions are traditional approaches in medicinal chemistry. Ring size, however, is rarely able to be leveraged as an independent variable because most hits lack the symmetry required for such a study. Our discovery that the cyclic oligomeric depsipeptide ent-verticilide inhibits mammalian cardiac ryanodine receptor calcium release channels with submicromolar potency provided an opportunity to explore ring size as a variable, independent of other structural or functional group changes. We report here that ring size can be a critical independent variable, suggesting that modest conformational changes alone can dramatically affect potency.
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Affiliation(s)
- Abigail N. Smith
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Daniel J. Blackwell
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37235, United States
| | - Bjorn C. Knollmann
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37235, United States
| | - Jeffrey N. Johnston
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
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7
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Smith AN, Johnston JN. The Formation of Impossible Rings in Macrocyclooligomerizations for Cyclodepsipeptide Synthesis: The 18-from-12 Paradox. J Org Chem 2021; 86:7904-7919. [PMID: 34097410 DOI: 10.1021/acs.joc.0c03069] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A reinvestigation into the macrocyclooligomerization (MCO) of a tetradepsipeptide is reported, uncovering a paradox in which the MCO of depsipeptide monomers can produce "impossible" ring sizes: a 12-atom chain produced the expected 24-membered ring, alongside unexpected 18- and 30-membered cyclic oligomeric depsipeptides (CODs). We report an alternative preparation of authentic 18- and 36-membered macrocycles for this case using a stepwise synthesis that provides definitive analytical characterization for each ring size. Our investigation yields a recharacterization and reassignment of two macrocycles originally reported in this MCO series, along with updated yields and isothermal titration calorimetry data after implementation of new critical protocols for purification and subsequent analysis. Initial studies to probe this mechanistic conundrum are described.
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Affiliation(s)
- Abigail N Smith
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Jeffrey N Johnston
- Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
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8
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Batiste SM, Johnston JN. Correction to "Evidence for Ion-Templation During Macrocyclooligomerization of Depsipeptides". J Am Chem Soc 2021; 143:6701. [PMID: 33881852 DOI: 10.1021/jacs.1c03371] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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9
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Watanabe A, Noguchi Y, Hirose T, Monma S, Satake Y, Arai T, Masuda K, Murashima N, Shiomi K, Ōmura S, Sunazuka T. Efficient synthesis of a ryanodine binding inhibitor verticilide using two practical approaches. Tetrahedron Lett 2020. [DOI: 10.1016/j.tetlet.2020.151699] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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10
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Unnatural verticilide enantiomer inhibits type 2 ryanodine receptor-mediated calcium leak and is antiarrhythmic. Proc Natl Acad Sci U S A 2019; 116:4810-4815. [PMID: 30792355 DOI: 10.1073/pnas.1816685116] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Ca2+ leak via ryanodine receptor type 2 (RyR2) can cause potentially fatal arrhythmias in a variety of heart diseases and has also been implicated in neurodegenerative and seizure disorders, making RyR2 an attractive therapeutic target for drug development. Here we synthesized and investigated the fungal natural product and known insect RyR antagonist (-)-verticilide and several congeners to determine their activity against mammalian RyR2. Although the cyclooligomeric depsipeptide natural product (-)-verticilide had no effect, its nonnatural enantiomer [ent-(+)-verticilide] significantly reduced RyR2-mediated spontaneous Ca2+ leak both in cardiomyocytes from wild-type mouse and from a gene-targeted mouse model of Ca2+ leak-induced arrhythmias (Casq2-/-). ent-(+)-verticilide selectively inhibited RyR2-mediated Ca2+ leak and exhibited higher potency and a distinct mechanism of action compared with the pan-RyR inhibitors dantrolene and tetracaine and the antiarrhythmic drug flecainide. ent-(+)-verticilide prevented arrhythmogenic membrane depolarizations in cardiomyocytes without significant effects on the cardiac action potential and attenuated ventricular arrhythmia in catecholamine-challenged Casq2-/- mice. These findings indicate that ent-(+)-verticilide is a potent and selective inhibitor of RyR2-mediated diastolic Ca2+ leak, making it a molecular tool to investigate the therapeutic potential of targeting RyR2 hyperactivity in heart and brain pathologies. The enantiomer-specific activity and straightforward chemical synthesis of (unnatural) ent-(+)-verticilide provides a compelling argument to prioritize ent-natural product synthesis. Despite their general absence in nature, the enantiomers of natural products may harbor unprecedented activity, thereby leading to new scaffolds for probe and therapeutic development.
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11
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Abstract
A biomimetic one-step ligase-catalyzed cyclo-oligomerization mediated by butelase 1, an Asn/Asp-specific ligase, is introduced that is time-, concentration-, length-, and sequence-dependent. This reaction yields cyclic mono-, di-, tri-, and tetramers from peptide precursors containing 3-15 amino acids ended with Asn and a His-Val tail. The cyclomonomers were favored when the peptide lengths were >9 amino acids. A turn-forming Pro residue at the P2 position favored the formation of higher-order cyclo-oligomers.
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Affiliation(s)
- Xinya Hemu
- School of Biological Sciences , Nanyang Technological University , 60 Nanyang Drive , Singapore 637551
| | - Xiaohong Zhang
- School of Biological Sciences , Nanyang Technological University , 60 Nanyang Drive , Singapore 637551
| | - James P Tam
- School of Biological Sciences , Nanyang Technological University , 60 Nanyang Drive , Singapore 637551
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12
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Fournier J, Chen K, Mailyan AK, Jackson JJ, Buckman BO, Emayan K, Yuan S, Rajagopalan R, Misialek S, Adler M, Blaesse M, Griessner A, Zakarian A. Total Synthesis of Covalent Cysteine Protease Inhibitor N-Desmethyl Thalassospiramide C and Crystallographic Evidence for Its Mode of Action. Org Lett 2019; 21:508-512. [DOI: 10.1021/acs.orglett.8b03821] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jeremy Fournier
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93111, United States
| | - Karen Chen
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93111, United States
| | - Artur K. Mailyan
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93111, United States
| | - Jeffrey J. Jackson
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93111, United States
| | - Brad O. Buckman
- Blade Therapeutics, 442 Littlefield Avenue, South San Francisco, California 94080, United States
| | - Kumar Emayan
- Bayside Pharma, 2600 Hilltop Drive, Richmond, California 94806, United States
| | - Shendong Yuan
- Bayside Pharma, 2600 Hilltop Drive, Richmond, California 94806, United States
| | - Ravi Rajagopalan
- Blade Therapeutics, 442 Littlefield Avenue, South San Francisco, California 94080, United States
| | - Shawn Misialek
- Blade Therapeutics, 442 Littlefield Avenue, South San Francisco, California 94080, United States
| | - Marc Adler
- ChemPartner, 280 Utah Avenue Suite 100, South San Francisco, California 94080, United States
| | - Michael Blaesse
- Proteros Biostructures GmbH, Bunsenstraße 7 a, 82152 Planegg-Martinsried, Germany
| | - Andreas Griessner
- Proteros Biostructures GmbH, Bunsenstraße 7 a, 82152 Planegg-Martinsried, Germany
| | - Armen Zakarian
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93111, United States
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13
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Batiste SM, Johnston JN. Evidence for Ion-Templation During Macrocyclooligomerization of Depsipeptides. J Am Chem Soc 2018; 140:4560-4568. [PMID: 29565576 PMCID: PMC5996984 DOI: 10.1021/jacs.7b13148] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The ion-mediated Mitsunobu macrocyclooligomerization (M-MCO) reaction of hydroxy acid depsipeptides provides small collections of cyclic depsipeptides with good mass recovery. The approach can produce good yields of a single macrocycle or provide rapid access to multiple oligomeric macrocycles in good overall yield. While Lewis acidic alkali metal salts are known to play a role in the outcome of MCO reactions, it is unclear whether their effect is due to an organizational (e.g., templating) mechanism. Isothermal titration calorimetry (ITC) was used to study macrocycle-metal ion binding interactions, and this report correlates these thermodynamic measurements to the (kinetically determined) size distributions of depsipeptides formed during a Mitsunobu-based macrocyclooligomerization (MCO). Key trends have been identified in quantitative metal ion-cyclic depsipeptide binding affinity ( Ka), enthalpy of binding (Δ H), and stoichiometry of complexation across discrete series of macrocycles, and they provide the first analytical platform to rationally select a metal-ion template for a targeted size regime of cyclic oligomeric depsipeptides.
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Affiliation(s)
- Suzanne M Batiste
- Department of Chemistry and Vanderbilt Institute of Chemical Biology , Vanderbilt University , Nashville , Tennessee 37235-1822 , United States
| | - Jeffrey N Johnston
- Department of Chemistry and Vanderbilt Institute of Chemical Biology , Vanderbilt University , Nashville , Tennessee 37235-1822 , United States
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14
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Boecker S, Grätz S, Kerwat D, Adam L, Schirmer D, Richter L, Schütze T, Petras D, Süssmuth RD, Meyer V. Aspergillus niger is a superior expression host for the production of bioactive fungal cyclodepsipeptides. Fungal Biol Biotechnol 2018; 5:4. [PMID: 29507740 PMCID: PMC5833056 DOI: 10.1186/s40694-018-0048-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 02/03/2018] [Indexed: 02/06/2023] Open
Abstract
Background Fungal cyclodepsipeptides (CDPs) are non-ribosomally synthesized peptides produced by a variety of filamentous fungi and are of interest to the pharmaceutical industry due to their anticancer, antimicrobial and anthelmintic bioactivities. However, both chemical synthesis and isolation of CDPs from their natural producers are limited due to high costs and comparatively low yields. These challenges might be overcome by heterologous expression of the respective CDP-synthesizing genes in a suitable fungal host. The well-established industrial fungus Aspergillus niger was recently genetically reprogrammed to overproduce the cyclodepsipeptide enniatin B in g/L scale, suggesting that it can generally serve as a high production strain for natural products such as CDPs. In this study, we thus aimed to determine whether other CDPs such as beauvericin and bassianolide can be produced with high titres in A. niger, and whether the generated expression strains can be used to synthesize new-to-nature CDP derivatives. Results The beauvericin and bassianolide synthetases were expressed under control of the tuneable Tet-on promoter, and titres of about 350–600 mg/L for bassianolide and beauvericin were achieved when using optimized feeding conditions, respectively. These are the highest concentrations ever reported for both compounds, whether isolated from natural or heterologous expression systems. We also show that the newly established Tet-on based expression strains can be used to produce new-to-nature beauvericin derivatives by precursor directed biosynthesis, including the compounds 12-hydroxyvalerate-beauvericin and bromo-beauvericin. By feeding deuterated variants of one of the necessary precursors (d-hydroxyisovalerate), we were able to purify deuterated analogues of beauvericin and bassianolide from the respective A. niger expression strains. These deuterated compounds could potentially be used as internal standards in stable isotope dilution analyses to evaluate and quantify fungal spoilage of food and feed products. Conclusion In this study, we show that the product portfolio of A. niger can be expanded from enniatin to other CDPs such as beauvericin and bassianolide, as well as derivatives thereof. This illustrates the capability of A. niger to produce a range of different peptide natural products in titres high enough to become industrially relevant. Electronic supplementary material The online version of this article (10.1186/s40694-018-0048-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Simon Boecker
- 1Department Biological Chemistry, Institute of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany.,2Department Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany
| | - Stefan Grätz
- 1Department Biological Chemistry, Institute of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Dennis Kerwat
- 1Department Biological Chemistry, Institute of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Lutz Adam
- 1Department Biological Chemistry, Institute of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - David Schirmer
- 1Department Biological Chemistry, Institute of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Lennart Richter
- 1Department Biological Chemistry, Institute of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Tabea Schütze
- 2Department Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany
| | - Daniel Petras
- 1Department Biological Chemistry, Institute of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Roderich D Süssmuth
- 1Department Biological Chemistry, Institute of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623 Berlin, Germany
| | - Vera Meyer
- 2Department Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany
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