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Abstract
Verruculogens are rare fumitremorgin alkaloids that contain a highly unusual eight-membered endoperoxide. In this paper, we report a concise chemoenzymatic synthesis of 13-oxoverruculogen using enzymatic C-H peroxidation and rhodium-catalyzed C-C bond activation reactions to install the eight-membered endoperoxide and the pentacyclic core of the natural product, respectively. Our strategy involves the use of 13-epi-fumitremorgin B as a substrate analog for endoperoxidation by verruculogen synthase, FtmOx1. The resulting product, 13-epi-verruculogen, is the first unnatural endoperoxide generated by FtmOx1 and is used in the first synthesis of 13-oxoverruculogen. This strategy enables a 10-step synthesis of this natural product from commercially available starting materials and illustrates a hybrid approach utilizing biocatalytic and transition-metal-catalyzed reactions to access challenging alkaloid architectures. Moreover, this work demonstrates the use of native enzyme promiscuity as a viable strategy for the chemoenzymatic synthesis of natural products.
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Affiliation(s)
- Jun Yang
- Brandeis University, Edison-Lecks Laboratory, Waltham, Massachusetts 02453, United States
| | - Brandon Singh
- Brandeis University, Edison-Lecks Laboratory, Waltham, Massachusetts 02453, United States
| | - Gabriel Cohen
- Brandeis University, Edison-Lecks Laboratory, Waltham, Massachusetts 02453, United States
| | - Chi P Ting
- Brandeis University, Edison-Lecks Laboratory, Waltham, Massachusetts 02453, United States
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Xuan J, Haelsig KT, Sheremet M, Machicao PA, Maimone TJ. Evolution of a Synthetic Strategy for Complex Polypyrrole Alkaloids: Total Syntheses of Curvulamine and Curindolizine. J Am Chem Soc 2021; 143:2970-2983. [PMID: 33570388 DOI: 10.1021/jacs.0c13465] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Structurally unprecedented antibacterial alkaloids containing multiple electron-rich pyrrole units have recently been isolated from Curvularia sp. and Bipolaris maydis fungi. This article documents the evolution of a synthetic program aimed at accessing the flagship metabolites curvulamine and curindolizine which are presumably a dimer and trimer of a C10N biosynthetic building block, respectively. Starting with curvulamine, we detail several strategies to merge two simple, bioinspired fragments, which while ultimately unsuccessful, led us toward a pyrroloazepinone building block-based strategy and an improved synthesis of this 10π-aromatic heterocycle. A two-step annulation process was then designed to forge a conserved tetracyclic bis-pyrrole architecture and advanced into a variety of late-stage intermediates; unfortunately, however, a failed decarboxylation thwarted the total synthesis of curvulamine. By tailoring our annulation precursors, success was ultimately found through the use of a cyanohydrin nucleophile which enabled a 10-step total synthesis of curvulamine. Attempts were then made to realize a biomimetic coupling of curvulamine with an additional C10N fragment to arrive at curindolizine, the most complex family member. Although unproductive, we developed a 14-step total synthesis of this alkaloid through an abiotic coupling approach. Throughout this work, effort was made to harness and exploit the innate reactivity of the pyrrole nucleus, an objective which has uncovered many interesting findings in the chemistry of this reactive heterocycle.
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Affiliation(s)
| | | | | | | | - Thomas J Maimone
- Department of Chemistry, University of California, Berkeley, 826 Latimer Hall, Berkeley, California 94720, United States
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3
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Patel OPS, Beteck RM, Legoabe LJ. Exploration of artemisinin derivatives and synthetic peroxides in antimalarial drug discovery research. Eur J Med Chem 2021; 213:113193. [PMID: 33508479 DOI: 10.1016/j.ejmech.2021.113193] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 12/04/2020] [Accepted: 01/11/2021] [Indexed: 12/22/2022]
Abstract
Malaria is a life-threatening infectious disease caused by protozoal parasites belonging to the genus Plasmodium. It caused an estimated 405,000 deaths and 228 million malaria cases globally in 2018 as per the World Malaria Report released by World Health Organization (WHO) in 2019. Artemisinin (ART), a "Nobel medicine" and its derivatives have proven potential application in antimalarial drug discovery programs. In this review, antimalarial activity of the most active artemisinin derivatives modified at C-10/C-11/C-16/C-6 positions and synthetic peroxides (endoperoxides, 1,2,4-trioxolanes, 1,2,4-trioxanes, and 1,2,4,5-tetraoxanes) are systematically summarized. The developmental trend of ART derivatives, and cyclic peroxides along with their antimalarial activity and how the activity is affected by structural variations on different sites of the compounds are discussed. This compilation would be very useful towards scaffold hopping aimed at avoiding the unnecessary complexity in cyclic peroxides, and ultimately act as a handy resource for the development of potential chemotherapeutics against Plasmodium species.
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Affiliation(s)
- Om P S Patel
- Centre of Excellence for Pharmaceutical Sciences, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa.
| | - Richard M Beteck
- Centre of Excellence for Pharmaceutical Sciences, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa
| | - Lesetja J Legoabe
- Centre of Excellence for Pharmaceutical Sciences, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa.
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Madhav H, Hoda N. An insight into the recent development of the clinical candidates for the treatment of malaria and their target proteins. Eur J Med Chem 2020; 210:112955. [PMID: 33131885 DOI: 10.1016/j.ejmech.2020.112955] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 10/08/2020] [Accepted: 10/19/2020] [Indexed: 01/18/2023]
Abstract
Malaria is an endemic disease, prevalent in tropical and subtropical regions which cost half of million deaths annually. The eradication of malaria is one of the global health priority nevertheless, current therapeutic efforts seem to be insufficient due to the emergence of drug resistance towards most of the available drugs, even first-line treatment ACT, unavailability of the vaccine, and lack of drugs with a new mechanism of action. Intensification of antimalarial research in recent years has resulted into the development of single dose multistage therapeutic agents which has advantage of overcoming the antimalarial drug resistance. The present review explored the current progress in the development of new promising antimalarials against prominent target proteins that have the potential to be a clinical candidate. Here, we also reviewed different aspects of drug resistance and highlighted new drug candidates that are currently in a clinical trial or clinical development, along with a few other molecules with excellent antimalarial activity overs ACTs. The summarized scientific value of previous approaches and structural features of antimalarials related to the activity are highlighted that will be helpful for the development of next-generation antimalarials.
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Affiliation(s)
- Hari Madhav
- Drug Design and Synthesis Laboratory, Department of Chemistry, Jamia Millia Islamia (A Central University), New Delhi, 110025, India.
| | - Nasimul Hoda
- Drug Design and Synthesis Laboratory, Department of Chemistry, Jamia Millia Islamia (A Central University), New Delhi, 110025, India.
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Harmange Magnani CS, Thach DQ, Haelsig KT, Maimone TJ. Syntheses of Complex Terpenes from Simple Polyprenyl Precursors. Acc Chem Res 2020; 53:949-961. [PMID: 32202757 DOI: 10.1021/acs.accounts.0c00055] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
From structure elucidation and biogenesis to synthetic methodology and total synthesis, terpene natural products have profoundly influenced the development of organic chemistry. Moreover, their myriad functional attributes range from fragrance to pharmaceuticals and have had great societal impact. Ruzicka's formulation of the "biogenetic isoprene rule," a Nobel Prize winning discovery now over 80 years old, allowed for identification of higher order terpene (aka "isoprenoid") structures from simple five-carbon isoprene fragments. Notably, the isoprene rule still holds pedagogical value to students of organic chemistry today. Our laboratory has completed syntheses of over two dozen terpene and meroterpene structures to date, and the isoprene rule has served as a key pattern recognition tool for our synthetic planning purposes. At the strategic level, great opportunity exists in finding unique and synthetically simplifying ways to connect the formal C5 isoprene fragments embedded in terpenes. Biomimetic cationic polyene cyclizations represent the earliest incarnation of this idea, which has facilitated expedient routes to certain terpene polycycle classes. Nonetheless, a large swath of terpene chemical space remains inaccessible using this approach.In this Account, we describe strategic insight into our endeavors in terpene synthesis published over the last five years. We show how biosynthetic understanding, combined with a desire to utilize abundant and inexpensive [C5]n building blocks, has led to efficient, abiotic syntheses of multiple complex terpenes with disparate ring systems. Informed by nature, but unconstrained by its processes, our synthetic assembly exploits chemical reactivity across diverse reaction types-including radical, anionic, pericyclic, and metal-mediated transformations.First, we detail an eight-step synthesis of the cembrane diterpene chatancin from dihydrofarnesal using a bioinspired-but not -mimetic-cycloaddition. Next, we describe the assembly of the antimalarial cardamom peroxide using a polyoxygenation cascade to fuse multiple units of molecular oxygen onto a dimeric skeleton. This three-to-four-step synthesis arises from (-)-myrtenal, an inexpensive pinene oxidation product. We then show how a radical cyclization cascade can forge the hallmark cyclooctane ring system of the complex sesterterpene 6-epi-ophiobolin N from two simple polyprenyl precursors, (-)-linalool and farnesol. To access the related, more complex metabolite 6-epi-ophiobolin A, we exploited the plasticity of our synthetic route and found that use of geraniol (C10) rather than farnesol (C15) gave us the flexibility needed to address the additional oxidation found in this congener. Following this work, we describe two strategies to access several guaianolide sesquiterpenes. Retrosynthetic disconnection to monoterpenes, carvone or (-)-linalool, coupled with a powerful allylation strategy allowed us to address guaianolides with disparate stereochemical motifs. Finally, we examine a semisynthetic approach to the illicium sesquiterpenes from the abundant 15-carbon feedstock terpene (+)-cedrol using an abiotic ring shift and multiple C-H oxidation reactions inspired by a postulated biosynthesis of this natural product class.
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Affiliation(s)
| | - Danny Q. Thach
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720, United States
| | - Karl T. Haelsig
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720, United States
| | - Thomas J. Maimone
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720, United States
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Elliott E, Chassagne F, Aubouy A, Deharo E, Souvanasy O, Sythamala P, Sydara K, Lamxay V, Manithip C, Torres JA, Bourdy G. Forest Fevers: traditional treatment of malaria in the southern lowlands of Laos. JOURNAL OF ETHNOPHARMACOLOGY 2020; 249:112187. [PMID: 31476439 DOI: 10.1016/j.jep.2019.112187] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 08/12/2019] [Accepted: 08/26/2019] [Indexed: 05/20/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Malaria is still a highly challenging public health issue in southern Lao PDR, with increasing cases of artemisinin resistance and Plasmodium vivax infections which are more complicated to treat. Traditional medicine has a long history of use in Laos, and is primarily practised by traditional village healers, who possess unique bodies of transmitted knowledge focused on herbal prescriptions, including those for the treatment of malaria. Villagers also use plants for healthcare in the home. The aim of the study is to document local fever concepts and use of herbal remedies, and examine whether they may have potential as complementary treatments against malaria. MATERIALS AND METHODS The study took place in Champasak province in the far south of Laos, in primarily lowland areas. First, 35 traditional healers across the 10 districts of the province were interviewed to elicit details about knowledge and treatment of fevers. Second, a household survey was conducted in a village in a malaria-endemic area; 97 households were interviewed on fever incidence, differentiation, treatment-seeking behaviour and knowledge of plant-based remedies for fevers. Plants indicated by both healers and villagers were collected and voucher specimens deposited in the herbarium of the National University of Laos for identification. RESULTS Malaria is a well-known pathology among the healers and villagers of lowland Champasak province; biomedical treatments are preferentially used, but traditional medicine is a popular complementary method, especially in chronic cases with additional symptoms. 30 different fever types were recorded, which were usually named symptomatically, and grouped into 12 categories. Some were described as forms of malaria, which was conceived as a dynamic, changing pathology affecting many body systems. Healers formulate treatments based on symptoms and the person's constitution, and with the intention of creating specific pharmacological actions associated with temperature or flavours. 11 of the healers gave prescriptions for malaria (27 in total), including 47 identified plant species. The most-used plants (4 or more use-reports) were also the most cited in the literature for use against malaria, demonstrating a correspondence between Lao healers and other traditional medical systems. Furthermore, some of these species show promising results for future research, especially Amorphophallus paeniifolius (Dennst.) Nicolson and Alocasia macrorrhizos (L.) G. Don. CONCLUSION Traditional healers are important actors in the treatment of malaria in southern Laos, and herbal remedies should be evaluated further by the use of reverse treatment outcome trials, especially those which may be of use as complementary remedies in treating P. vivax. Initiatives on knowledge transmission, medicinal plant conservation and healthcare integration are also urgently needed.
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Affiliation(s)
| | - François Chassagne
- UMR 152 Pharmadev, IRD, Université de Toulouse, France; Center for the Study of Human Health, Emory University, Atlanta, GA, USA
| | - Agnès Aubouy
- UMR 152 Pharmadev, IRD, Université de Toulouse, France
| | - Eric Deharo
- UMR 152 Pharmadev, IRD, Université de Toulouse, France
| | - Outhay Souvanasy
- Department of Traditional Medicine, Champasak Regional Hospital, Pakse, Lao Peoples Democratic Republic
| | - Phaiboun Sythamala
- Department of Traditional Medicine, Champasak Regional Hospital, Pakse, Lao Peoples Democratic Republic
| | - Kongmany Sydara
- Institute of Traditional Medicine, Vientiane, Lao Peoples Democratic Republic
| | - Vichith Lamxay
- Department of Biology, Faculty of Natural Sciences, National University of Laos, Vientiane, Lao Peoples Democratic Republic
| | - Chantanom Manithip
- Faculty of Pharmacy, University of Health Sciences, Vientiane, Lao Peoples Democratic Republic
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Hu X, Musacchio AJ, Shen X, Tao Y, Maimone TJ. Allylative Approaches to the Synthesis of Complex Guaianolide Sesquiterpenes from Apiaceae and Asteraceae. J Am Chem Soc 2019; 141:14904-14915. [PMID: 31448610 DOI: 10.1021/jacs.9b08001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
With hundreds of unique members isolated to date, guaianolide lactones represent a particularly prolific class of terpene natural products. Given their extensive documented therapeutic properties and fascinating chemical structures, these metabolites have captivated the synthetic chemistry community for many decades. As a result of divergent biosynthetic pathways, which produce a wide array of stereochemical and oxidative permutations, a unifying synthetic pathway to this broad family of natural products is challenging. Herein we document the evolution of a chiral-pool-based synthetic program aimed at accessing an assortment of guaianolides, particularly those from the plant family Apiaceae as well as Asteraceae, members of which possess distinct chemical substructures and necessitate deviating synthetic platforms. An initial route employing the linear monoterpene linalool generated a lower oxidation state guaianolide but was not compatible with the majority of family members. A double-allylation disconnection using a carvone-derived fragment was then developed to access first an Asteraceae-type guaianolide and then various Apiaceae congeners. Finally, using these findings in conjunction with a tandem polyoxygenation cascade, we developed a pathway to highly oxygenated nortrilobolide. A variety of interesting observations in metal-mediated aldehyde allylation and alkene polyoxygenation are reported and discussed.
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Affiliation(s)
| | | | | | | | - Thomas J Maimone
- Department of Chemistry , University of California, Berkeley , 826 Latimer Hall , Berkeley , California 94720 , United States
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