1
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Kaneko M, Li Z, Burk M, Colis L, Herzon SB. Synthesis and Biological Evaluation of (2 S,2' S)-Lomaiviticin A. J Am Chem Soc 2021; 143:1126-1132. [PMID: 33410680 PMCID: PMC8174553 DOI: 10.1021/jacs.0c11960] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
(-)-Lomaiviticin A (1) is a genotoxic C2-symmetric metabolite that arises from the formal dimerization of two bis(glycosylated) diazotetrahydrobenzo[b]fluorenes. Here we present a synthesis of the monomer 17 and its coupling to form (2S,2'S)-lomaiviticin A (4), an unnatural diastereomer of 1. (2S,2'S)-Lomaiviticin A (4) is significantly less genotoxic, a result we attribute to changes in the orientation of the diazofluorene and carbohydrate residues, relative to 1. These data bring the importance of the configuration of the conjoining bond to light and place the total synthesis of 1 itself within reach.
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Affiliation(s)
- Miho Kaneko
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Zhenwu Li
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Matthew Burk
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Laureen Colis
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Seth B. Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
- Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520, United States
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2
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Abstract
(-)-Lomaiviticin A (4) is a complex C2-symmetric bacterial metabolite that contains two diazofluorene functional groups. The diazofluorene consists of naphthoquinone, cyclopentadiene, and diazo substituents fused through a σ- and π-bonding network. Additionally, (-)-lomaiviticin A (4) is a potent cytotoxin, with half-maximal inhibitory potency (IC50) values in the low nanomolar range against many cancer cell lines. Because of limitations in supply, its mechanism of action had remained a "black box" since its isolation in the early 2000s. In this Account, I describe how studies directed toward the total synthesis of (-)-lomaiviticin A (4) provided a platform to elucidate the emergent properties of this metabolite and thereby connect chemical reactivity with cellular phenotype. We first developed a convergent strategy to prepare the diazofluorene (9 + 10 → 13). We then adapted this chemistry to the synthesis of lomaiviticin aglycon (21/22) and the natural monomeric diazofluorene (-)-kinamycin F (3). The key step in the lomaiviticin aglycon (21/22) synthesis involved the stereoselective oxidative coupling of two monomeric diazofluorenes (2 × 18 → 20) to establish the cojoining carbon-carbon bond of the target. As the absolute stereochemistry of the aglycon and carbohydrate residues of (-)-lomaiviticin A (4) were unknown, we developed a semisynthetic route to the metabolite that proceeds in one step and 42% yield by diazo transfer to the more abundant isolate (-)-lomaiviticin C (6). This allowed us to complete the stereochemical assignment of (-)-lomaiviticin A (4) and provided a renewable source of material. Using this material, we established that the remarkable cytotoxic effects of (-)-lomaiviticin A (4) derive from the induction of highly toxic double-strand breaks (DSBs) in DNA. At the molecular level, 1,7-nucleophilic additions to each electrophilic diazofluorene trigger homolytic decomposition pathways that produce sp2 radicals at the carbon atoms of each diazo group. These radicals abstract hydrogen atoms from the deoxyribose of DNA, a process known to initiate strand cleavage. NMR spectroscopy and molecular mechanics simulations were used to elucidate the mode of DNA binding. These studies showed that both diazofluorenes of (-)-lomaiviticin A (4) penetrate into the duplex. This mode of non-covalent binding places each diazo carbon atom in close proximity to each DNA strand. Throughout these studies, isolates containing one diazofluorene, such as (-)-lomaiviticin C (6) and (-)-kinamycin C (2), were used as controls. Consistent with our mechanistic model, these compounds do not induce DSBs in DNA and are several orders of magnitude less potent. Reactivity studies suggest that (-)-lomaiviticin A (4) is more electrophilic than simple monomeric diazofluorenes. We attribute this to through-space delocalization of the developing negative charge in the transition state for 1,7-addition. Consistent with this mechanism of action, (-)-lomaiviticin A (4) displays selective low-picomolar potencies toward DNA DSB repair-deficient cell types. The emergent properties of (-)-lomaiviticin A (4) derive from the specific arrangement of diazo, naphthoquinone, cyclopentadiene, and ketone functional groups. These functional groups work together to yield, essentially, a masked vinyl radical that can be exposed under biological conditions. Furthermore, the rotational symmetry of the metabolite, deriving from dimerization, allows it to interact with the antiparallel symmetry of DNA and affect cleavage of the duplex.
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Affiliation(s)
- Seth B. Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States. Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520, United States
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3
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Waldman AJ, Ng TL, Wang P, Balskus EP. Heteroatom-Heteroatom Bond Formation in Natural Product Biosynthesis. Chem Rev 2017; 117:5784-5863. [PMID: 28375000 PMCID: PMC5534343 DOI: 10.1021/acs.chemrev.6b00621] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Natural products that contain functional groups with heteroatom-heteroatom linkages (X-X, where X = N, O, S, and P) are a small yet intriguing group of metabolites. The reactivity and diversity of these structural motifs has captured the interest of synthetic and biological chemists alike. Functional groups containing X-X bonds are found in all major classes of natural products and often impart significant biological activity. This review presents our current understanding of the biosynthetic logic and enzymatic chemistry involved in the construction of X-X bond containing functional groups within natural products. Elucidating and characterizing biosynthetic pathways that generate X-X bonds could both provide tools for biocatalysis and synthetic biology, as well as guide efforts to uncover new natural products containing these structural features.
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Affiliation(s)
- Abraham J. Waldman
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, United States
| | - Tai L. Ng
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, United States
| | - Peng Wang
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, United States
| | - Emily P. Balskus
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, United States
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4
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Abstract
Diazo groups have broad and tunable reactivity. That and other attributes endow diazo compounds with the potential to be valuable reagents for chemical biologists. The presence of diazo groups in natural products underscores their metabolic stability and anticipates their utility in a biological context. The chemoselectivity of diazo groups, even in the presence of azido groups, presents many opportunities. Already, diazo compounds have served as chemical probes and elicited novel modifications of proteins and nucleic acids. Here, we review advances that have facilitated the chemical synthesis of diazo compounds, and we highlight applications of diazo compounds in the detection and modification of biomolecules.
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Affiliation(s)
- Kalie A. Mix
- Department of Biochemistry, University of Wisconsin–Madison, 433 Babcock Drive, Madison, Wisconsin 53706, United States
| | - Matthew R. Aronoff
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Ronald T. Raines
- Department of Biochemistry, University of Wisconsin–Madison, 433 Babcock Drive, Madison, Wisconsin 53706, United States
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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5
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Xue M, Herzon SB. Mechanism of Nucleophilic Activation of (-)-Lomaiviticin A. J Am Chem Soc 2016; 138:15559-15562. [PMID: 27934014 DOI: 10.1021/jacs.6b09657] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
(-)-Lomaiviticin A (1) is a C2-symmetric cytotoxin that contains two diazofluorene functional groups and which induces double-strand breaks (DSBs) in DNA. Evidence suggests DNA cleavage is initiated by hydrogen atom abstraction from the deoxyribose backbone. Here we demonstrate the formation of the vinyl radicals 1· and 2· from 1 by 1,7-addition of thiols to the diazofluorenes. These radicals can affect hydrogen atom abstraction from methanol and acetone. The first addition of thiol to 1 proceeds at a much greater rate than the second. The diazosulfide 5 formed en route to 1· has been detected at -50 °C and undergoes decomposition to 1· with a half-life of 110 min at -20 °C under air. These data, which constitute the first direct evidence for the generation of 1· and 2· from 1, provide insights into the mechanism of DNA cleavage by 1.
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Affiliation(s)
- Mengzhao Xue
- Department of Chemistry, Yale University , New Haven, Connecticut 06520, United States
| | - Seth B Herzon
- Department of Chemistry, Yale University , New Haven, Connecticut 06520, United States.,Department of Pharmacology, Yale School of Medicine , New Haven, Connecticut 06520, United States
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6
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7
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Woo CM, Ranjan N, Arya DP, Herzon SB. Analysis of diazofluorene DNA binding and damaging activity: DNA cleavage by a synthetic monomeric diazofluorene. Angew Chem Int Ed Engl 2014; 53:9325-8. [PMID: 25044348 PMCID: PMC4206835 DOI: 10.1002/anie.201404137] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Indexed: 01/04/2023]
Abstract
The lomaiviticins and kinamycins are complex DNA damaging natural products that contain a diazofluorene functional group. Herein, we elucidate the influence of skeleton structure, ring and chain isomerization, D-ring oxidation state, and naphthoquinone substitution on DNA binding and damaging activity. We show that the electrophilicity of the diazofluorene appears to be a significant determinant of DNA damaging activity. These studies identify the monomeric diazofluorene 11 as a potent DNA cleavage agent in tissue culture. The simpler structure of 11 relative to the natural products establishes it as a useful lead for translational studies.
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Affiliation(s)
- Christina M. Woo
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06520-8107 (USA)
| | - Nihar Ranjan
- Department of Chemistry, Clemson University, Clemson, SC 29634 (USA)
| | - Dev P. Arya
- Department of Chemistry, Clemson University, Clemson, SC 29634 (USA)
| | - Seth B. Herzon
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06520-8107 (USA)
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8
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Woo CM, Ranjan N, Arya DP, Herzon SB. Analysis of Diazofluorene DNA Binding and Damaging Activity: DNA Cleavage by a Synthetic Monomeric Diazofluorene. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201404137] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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9
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Colis LC, Woo CM, Hegan DC, Li Z, Glazer PM, Herzon SB. The cytotoxicity of (-)-lomaiviticin A arises from induction of double-strand breaks in DNA. Nat Chem 2014; 6:504-10. [PMID: 24848236 PMCID: PMC4090708 DOI: 10.1038/nchem.1944] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 04/04/2014] [Indexed: 11/09/2022]
Abstract
The metabolite (-)-lomaiviticin A, which contains two diazotetrahydrobenzo[b]fluorene (diazofluorene) functional groups, inhibits the growth of cultured human cancer cells at nanomolar-picomolar concentrations; however, the mechanism responsible for the potent cytotoxicity of this natural product is not known. Here we report that (-)-lomaiviticin A nicks and cleaves plasmid DNA by a pathway that is independent of reactive oxygen species and iron, and that the potent cytotoxicity of (-)-lomaiviticin A arises from the induction of DNA double-strand breaks (dsbs). In a plasmid cleavage assay, the ratio of single-strand breaks (ssbs) to dsbs is 5.3 ± 0.6:1. Labelling studies suggest that this cleavage occurs via a radical pathway. The structurally related isolates (-)-lomaiviticin C and (-)-kinamycin C, which contain one diazofluorene, are demonstrated to be much less effective DNA cleavage agents, thereby providing an explanation for the enhanced cytotoxicity of (-)-lomaiviticin A compared to that of other members of this family.
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Affiliation(s)
- Laureen C Colis
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA
| | - Christina M Woo
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA
| | - Denise C Hegan
- Departments of Therapeutic Radiology and Genetics, Yale School of Medicine, New Haven, Connecticut 06520, USA
| | - Zhenwu Li
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA
| | - Peter M Glazer
- Departments of Therapeutic Radiology and Genetics, Yale School of Medicine, New Haven, Connecticut 06520, USA
| | - Seth B Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA
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10
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Wender PA, Donnelly AC, Loy BA, Near KE, Staveness D. Rethinking the Role of Natural Products: Function-Oriented Synthesis, Bryostatin, and Bryologs. METHODS AND PRINCIPLES IN MEDICINAL CHEMISTRY 2014. [DOI: 10.1002/9783527676545.ch14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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11
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Abbott GL, Wu X, Zhao Z, Guo L, Birman VB, Hasinoff BB, Dmitrienko GI. Prekinamycin and an isosteric-isoelectronic analogue exhibit comparable cytotoxicity towards K562 human leukemia cells. MEDCHEMCOMM 2014. [DOI: 10.1039/c4md00197d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The diazo functionality of the kinamycins may not be an absolute requirement for bioactivity.
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Affiliation(s)
- Glenn L. Abbott
- Department of Chemistry
- University of Waterloo
- Waterloo, Canada
| | - Xing Wu
- Faculty of Pharmacy
- Apotex Centre
- University of Manitoba
- Winnipeg, Canada
| | - Zhufeng Zhao
- Department of Chemistry
- Washington University
- St Louis, USA
| | - Lei Guo
- Department of Chemistry
- Washington University
- St Louis, USA
| | | | - Brian B. Hasinoff
- Faculty of Pharmacy
- Apotex Centre
- University of Manitoba
- Winnipeg, Canada
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12
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Feldman KS, Selfridge BR. Synthesis studies on the lomaiviticin A aglycone core: development of a divergent, two-directional strategy. J Org Chem 2013; 78:4499-511. [PMID: 23581811 DOI: 10.1021/jo4005074] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The enantiomer of the bicyclic lomaiviticin aglycone A core was prepared via a two-directional, divergent approach featuring (1) a double Ireland Claisen rearrangement to establish key core bonds with correct relative stereochemistry and (2) a double olefin metathesis reaction to deliver both cyclohexene rings of the target.
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Affiliation(s)
- Ken S Feldman
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
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13
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Feldman KS, Selfridge BR. Enantioselective Synthesis of the ent-Lomaiviticin A Bicyclic Core. Org Lett 2012; 14:5484-7. [DOI: 10.1021/ol302567f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ken S. Feldman
- Chemistry Department, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Brandon R. Selfridge
- Chemistry Department, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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14
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Woo CM, Gholap SL, Lu L, Kaneko M, Li Z, Ravikumar PC, Herzon SB. Development of enantioselective synthetic routes to (-)-kinamycin F and (-)-lomaiviticin aglycon. J Am Chem Soc 2012; 134:17262-73. [PMID: 23030272 PMCID: PMC3505684 DOI: 10.1021/ja307497h] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The development of enantioselective synthetic routes to (-)-kinamycin F (9) and (-)-lomaiviticin aglycon (6) are described. The diazotetrahydrobenzo[b]fluorene (diazofluorene) functional group of the targets was prepared by fluoride-mediated coupling of a β-trimethylsilylmethyl-α,β-unsaturated ketone (38) with an oxidized naphthoquinone (19), palladium-catalyzed cyclization (39→37), and diazo transfer (37→53). The D-ring precursors 60 and 68 were prepared from m-cresol and 3-ethylphenol, respectively. Coupling of the β-trimethylsilylmethyl-α,β-unsaturated ketone 60 with the juglone derivative 61, cyclization, and diazo transfer provided the advanced diazofluorene 63, which was elaborated to (-)-kinamycin F (9) in three steps. The diazofluorene 87 was converted to the C(2)-symmetric lomaiviticin aglycon precursor 91 by enoxysilane formation and oxidative dimerization with manganese tris(hexafluoroacetylacetonate) (94, 26%). The stereochemical outcome in the coupling is attributed to the steric bias engendered by the mesityl acetal of 87 and contact ion pairing of the intermediates. The coupling product 91 was deprotected (tert-butylhydrogen peroxide, trifluoroacetic acid-dichloromethane) to form mixtures of the chain isomer of lomaiviticin aglycon 98 and the ring isomer 6. These mixtures converged on purification or standing to the ring isomer 6 (39-41% overall). The scope of the fluoride-mediated coupling process is delineated (nine products, average yield = 72%); a related enoxysilane quinonylation reaction is also described (10 products, average yield = 77%). We establish that dimeric diazofluorenes undergo hydrodediazotization 2-fold faster than related monomeric diazofluorenes. This enhanced reactivity may underlie the cytotoxic effects of (-)-lomaiviticin A (1). The simple diazofluorene 103 is a potent inhibitor of ovarian cancer stem cells (IC(50) = 500 nM).
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Affiliation(s)
- Christina M. Woo
- Department of Chemistry, Yale University, New Haven, CT 06520, United States
| | | | - Liang Lu
- Department of Chemistry, Yale University, New Haven, CT 06520, United States
| | - Miho Kaneko
- Department of Chemistry, Yale University, New Haven, CT 06520, United States
| | - Zhenwu Li
- Department of Chemistry, Yale University, New Haven, CT 06520, United States
| | - P. C. Ravikumar
- Department of Chemistry, Yale University, New Haven, CT 06520, United States
| | - Seth B. Herzon
- Department of Chemistry, Yale University, New Haven, CT 06520, United States
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15
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Woo CM, Beizer NE, Janso JE, Herzon SB. Isolation of Lomaiviticins C–E, Transformation of Lomaiviticin C to Lomaiviticin A, Complete Structure Elucidation of Lomaiviticin A, and Structure–Activity Analyses. J Am Chem Soc 2012; 134:15285-8. [DOI: 10.1021/ja3074984] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Christina M. Woo
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United
States
| | - Nina E. Beizer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United
States
| | - Jeffrey E. Janso
- Natural Products
− Worldwide
Medicinal Chemistry, Pfizer Worldwide Research and Development, 445 Eastern Point Road, Groton, Connecticut 06340, United States
| | - Seth B. Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United
States
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