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Thorat SS, Shimpi SP, Sambherao PI, Rama Krishna G, Kontham R. Regioselective Synthesis of Benzannulated [5,6]-Oxaspirolactones via Cu(II)-Catalyzed Cycloisomerization of 2-(5-Hydroxyalkynyl)benzoates. J Org Chem 2023. [PMID: 38010985 DOI: 10.1021/acs.joc.3c01751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Spiroketals and oxaspirolactones are widely found in biologically active natural products, serving as important structural motifs. In this study, we present a Cu(II)-catalyzed cascade cycloisomerization of 2-(5-hydroxyalkynyl)benzoates, enabling the regioselective synthesis of benzannulated [5,6]-oxaspirolactones containing an isochromen-1-one moiety. This strategy offers a rapid and efficient approach to access a diverse array of benzannulated [5,6]-oxaspirolactones. The methodology presented here showcases a broad substrate scope, delivering good yields and scalability up to gram scale. The structures of the oxaspirolactones were unequivocally confirmed through single-crystal X-ray analysis and by analogy using 1H and 13C{1H} NMR data.
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Affiliation(s)
- Sagar S Thorat
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Sagar P Shimpi
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Pooja I Sambherao
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Gamidi Rama Krishna
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
- Center for Materials Characterization, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
| | - Ravindar Kontham
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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Borade BR, Kontham R. Concise Total Synthesis of (+)-Lanceolactone A: Revision of Absolute Stereochemistry. J Org Chem 2022; 87:12867-12876. [PMID: 36170601 DOI: 10.1021/acs.joc.2c01450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A chiral-pool protecting-group-free five-step total synthesis of tetranorsesquiterpenoide (+)-lanceolactone A and all of its four stereoisomers using (S)-(+)-, and (R)-(-)-linalool (coriandrol) as building blocks is disclosed. The key steps involved in this synthetic route are regioselective ozonolysis, Au(I)-catalyzed cycloisomerization-induced construction of furan from alleneone, and dye-sensitized photo-oxidation (through 1O2; singlet oxygen) of hydroxyalkyl-tethered furan to access oxaspirolactone. After a thorough evaluation of electronic circular dichroism (ECD) and optical rotation data of all possible stereoisomers, the absolute configuration of natural lanceolactone A at the C4 and C7 positions has been assigned as (+)-(4S,7S), which is an enantiomer to the initially proposed structure (+)-(4R,7R). Further, these investigations led us to extend Feringa and Gawronski's CD correlation method to [5,5]- and [6,5]-oxaspirolactones.
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Affiliation(s)
- Balasaheb R Borade
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Ravindar Kontham
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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Mankad Y, Thorat SS, Das P, Rama Krishna G, Kontham R, Reddy DS. Ready Access to Benzannulated [5,5]-Oxaspirolactones Using Au(III)-Catalyzed Cascade Cyclizations. J Org Chem 2022; 87:3025-3041. [PMID: 35188770 DOI: 10.1021/acs.joc.1c02843] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This work showcases an unprecedented Au(III)-catalyzed cascade cyclization of 2-(4-hydroxyalkynyl)benzoates to access benzannulated [5,5]-oxaspirolactones related to biologically active natural products. This reaction proceeds through an initial 5-endo-dig mode of hydroalkoxylation of the alkynol segment to give the oxocarbenium species (via cyclic enol-ether) followed by the addition of carboxylate onto the oxocarbenium that delivers the oxaspirolactone scaffold. While testing this method's scope, we found that the steric and electronic environment of the hydroxyl group could alter the reaction pathway that delivers isochromenone through a competitive 6-endo-dig mode of attack of the carboxylate onto the tethered alkyne.
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Affiliation(s)
- Yash Mankad
- Natural Products and Medicinal Chemistry Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu-180001, India.,Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Sagar S Thorat
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Pronay Das
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Gamidi Rama Krishna
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.,Center for Materials Characterization, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India
| | - Ravindar Kontham
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - D Srinivasa Reddy
- Natural Products and Medicinal Chemistry Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu-180001, India.,Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
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Kataria P, Nomula R, Kontham R. Studies directed toward the synthesis of hedycoropyrans: total synthesis of des-hydroxy (-)-hedycoropyran B ( ent-rhoiptelol B). Org Biomol Chem 2022; 20:444-463. [PMID: 34904991 DOI: 10.1039/d1ob01972d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A full account of our efforts directed towards the synthesis of the diarylheptanoid-derived natural products hedycoropyrans that led to the total synthesis of ent-rhoiptelol B is described. In this endeavor, we have attempted two distinct synthetic strategies to access hedycoropyrans A and B, which led us to establish a facile synthetic route for des-hydroxy (-)-hedycoropyran B (ent-rhoiptelol B) from simple and readily accessible building blocks of 4-allylanisole and vanillin, employing Sharpless asymmetric epoxidation, CBS reduction, and an intramolecular AgOTf-catalyzed oxa-Michael reaction of suitably functionalized hydroxy-ynone as key transformations. The investigations disclosed herein will provide insights into designing novel synthetic routes for THP-DAH-derived natural products.
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Affiliation(s)
- Priyanka Kataria
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India. .,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Rajesh Nomula
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.
| | - Ravindar Kontham
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India. .,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
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Thorat SS, Rama Krishna G, Kontham R. Stereoselective Total Synthesis of (±)-Pleurospiroketals A and B. J Org Chem 2021; 86:13572-13582. [PMID: 34547199 DOI: 10.1021/acs.joc.1c01634] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A full account of our efforts toward the stereoselective total synthesis of sesquiterpenoid-derived natural products (±)-pleurospiroketals A and B is described. Commercially available 3-methyl-2-cyclohexenone and 2,2-dimethyloxirane were used as key building blocks, and the substrate-controlled stereoselection was exploited to access the entire stereochemistry of these natural products. Initially, a planned synthetic route involving a [6,5]-bicyclic lactone intermediate was found to be insurmountable, and the later strategy comprising OsO4-NMO-mediated dihydroxylation of 3-methyl-2-cyclohexenone, followed by Luche reduction, Eschenmoser methylenation, and Brønsted acid-induced spiroketalization steps, was ultimately identified as the reliable strategy.
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Affiliation(s)
- Sagar S Thorat
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Gamidi Rama Krishna
- Centre for Materials Characterization, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, 411008, India
| | - Ravindar Kontham
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
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Chatterjee S, Sahoo R, Nanda S. Recent reports on the synthesis of γ-butenolide, γ-alkylidenebutenolide frameworks, and related natural products. Org Biomol Chem 2021; 19:7298-7332. [PMID: 34612357 DOI: 10.1039/d1ob00875g] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
γ-Butenolides are fundamental frameworks found in many naturally occurring compounds, and they exhibit tremendous biological activities. γ-Butenolides also have proven their potential as useful synthetic intermediates in the total synthesis of natural compounds. Over the years, many γ-butenolide natural products have been isolated, having exocyclic γ-δ unsaturation in their structure. These natural products are collectively referred to as γ-alkylidenebutenolides. Considering the different biological profiles and wide-ranging structural diversity of the optically active γ-butenolide, the development of synthetic strategies for assembling such challenging scaffolds has attracted significant attention from synthetic chemists in recent times. In this report, a brief discussion will be provided to address isolation, biogenesis, and current state-of-the-art synthetic protocols for such molecules. This report aims to focus on synthetic strategies for γ-butenolides from 2010-2020 with a particular emphasis on γ-alkylidenebutenolides and related molecules. Metal-mediated catalytic transformation and organocatalysis are the two main reaction types that have been widely used to access such molecules. Mechanistic considerations, enantioselective synthesis, and practical applications of the reported procedures are also taken into consideration.
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Affiliation(s)
- Shrestha Chatterjee
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
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Mandal S, Thirupathi B. Strategies for the construction of γ-spirocyclic butenolides in natural product synthesis. Org Biomol Chem 2021; 18:5287-5314. [PMID: 32633316 DOI: 10.1039/d0ob00954g] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the last four decades, a number of γ-spirocyclic butenolide containing natural products, drugs, and medicinally useful synthetic compounds have been reported. In this review, we discuss diverse chemical approaches to synthesize γ-spiro butenolides and their application towards natural product synthesis. The collective perception of various methods may allow superior approaches capable of delivering efficient synthetic approaches to obtain γ-spiro butenolide comprising natural products and their hybrid analogues for further drug discovery and development.
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Affiliation(s)
- Sudip Mandal
- Department of Chemical Sciences, Indian Institute of Science Education and Research Berhampur, Transit Campus, Govt. ITI Building, NH 59, Engineering School Road, Ganjam-District, Berhampur 760 010, Odisha, India.
| | - Barla Thirupathi
- Department of Chemical Sciences, Indian Institute of Science Education and Research Berhampur, Transit Campus, Govt. ITI Building, NH 59, Engineering School Road, Ganjam-District, Berhampur 760 010, Odisha, India.
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Borade BR, Dixit R, Kontham R. Total Synthesis of Beshanzuenone D and Its Epimers and Abiespiroside A. Org Lett 2020; 22:8561-8565. [DOI: 10.1021/acs.orglett.0c03157] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Balasaheb R. Borade
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Ruchi Dixit
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Ravindar Kontham
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
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Synthetic methods for spirofuran-2(5H)-ones (microreview). Chem Heterocycl Compd (N Y) 2019. [DOI: 10.1007/s10593-019-02594-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Palange MN, Gonnade RG, Kontham R. TiCl 4-n-Bu 3N-mediated cascade annulation of ketones with α-ketoesters: a facile synthesis of highly substituted fused γ-alkylidene-butenolides. Org Biomol Chem 2019; 17:5749-5759. [PMID: 31124555 DOI: 10.1039/c9ob00649d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A facile protocol for the synthesis of highly substituted fused γ-alkylidene butenolides using direct annulation of ketones with α-ketoesters, which proceeds through TiCl4-n-Bu3N mediated aldol addition followed by an intramolecular enol-lactonization/cyclization cascade, is reported. Diverse 6-5, 7-5 and 8-5 fused bicyclic γ-ylidene butenolides and highly substituted monocyclic analogs related to biologically relevant natural products were prepared from readily accessible ketone and α-ketoester building blocks. The highly step-economic cascade nature, good substrate scope, easy access to complex products with good to excellent yields, gram-scalability, demonstration of synthetic utility, and unambiguous structural confirmation through X-ray crystallography analyses and analogy are the salient features of this work.
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Affiliation(s)
- Megha N Palange
- Organic Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune-411008, India.
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