1
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Bankar OS, Laha D, Meher KB, Bhat RG. Umpolung Reactivity of Diazo Arylidene Succinimides: Distal C-H Functionalization of α-Thiocarbonyls from the Reactive Carbenoid Center. Chem Asian J 2023; 18:e202300774. [PMID: 37828837 DOI: 10.1002/asia.202300774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/09/2023] [Accepted: 10/10/2023] [Indexed: 10/14/2023]
Abstract
Herein, for the first time we have explored the umpolung reactivity of the vinylogous carbon center of diazo arylidene succinimide (DAS) through rhodium catalysis to achieve [2,3]-Stevens rearrangement of α-thioether esters. The protocol has successfully demonstrated the distal C-H bond functionalization of the α-thioether esters. Alongside, the carbenoid reactivity of DAS has also been achieved with Doyle-Kirmse reaction of allyl/propargyl phenyl sulfides. The protocol proved to be practical to synthesize a wide variety of [2,3]-Stevens rearrangement products exclusively and the possible side products emanating from Pummerer rearrangement and [1,2]-Stevens rearrangement were not observed. This catalytic protocol works smoothly in environmentally benign solvent under open air to afford the corresponding desired products with excellent diastereo-, regio- and chemo-selectivities in good to excellent yields. The protocol also proved to be scalable on gram quantity.
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Affiliation(s)
- Onkar S Bankar
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, NCL Colony, Pashan, Pune, Maharashtra, 411008, India
| | - Debasish Laha
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, NCL Colony, Pashan, Pune, Maharashtra, 411008, India
| | - Kajal B Meher
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, NCL Colony, Pashan, Pune, Maharashtra, 411008, India
| | - Ramakrishna G Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, NCL Colony, Pashan, Pune, Maharashtra, 411008, India
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2
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Bhowmick A, Chatterjee A, Pathak SS, Bhat RG. A visible light-driven direct synthesis of industrially relevant glutaric acid diesters from aldehydes. Chem Commun (Camb) 2023; 59:11875-11878. [PMID: 37724011 DOI: 10.1039/d3cc02557h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/20/2023]
Abstract
A straightforward and practical method has been developed to access α-substituted glutaric diesters from acrylates and aldehydes using visible light, with Eosin Y facilitating hydrogen atom transfer (HAT) and subsequent Giese-type addition. Also, sunlight has been successfully used as an alternative sustainable light source. The method has also been explored to access substituted 4,5-dihydro-2H-pyridazinones, which have potential biological and industrial applications. Comprehensive mechanistic investigations have been carried out.
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Affiliation(s)
- Anindita Bhowmick
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Maharashtra, India.
| | - Abhijit Chatterjee
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Maharashtra, India.
| | - Sidharth S Pathak
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Maharashtra, India.
| | - Ramakrishna G Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Maharashtra, India.
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3
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Khade VV, Bhowmick A, Thube AS, Bhat RG. Direct Access to Strained Fused Dihalo-Aziridino Quinoxalinones via C3-Alkylation Followed by Tandem Cyclization. J Org Chem 2023. [PMID: 37262098 DOI: 10.1021/acs.joc.3c00033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Quinoxalinones are a privileged class of compounds, and their structural framework is found in many bioactive compounds, natural compounds, and pharmaceuticals. Quinoxalinone is a promising scaffold for different types of functionalization, and the slight modification of the quinoxalinone skeleton is known to offer a wide range of compounds for drug discovery. Owing to the importance of the quinoxalinone scaffold, we have developed a base-mediated protocol for the C3-alkylation of quinoxalinone followed by tandem cyclization to access novel types of strenuous and fused dihalo-aziridino-quinoxalinone heterocycles via the construction of C-C and C-N bonds. The protocol proved to be simple and practical to access desired fused quinoxalinone heterocycles in excellent yields (up to 98% yield). As an application, the highly functionalized fused dihalo-aziridino-quinoxalinone molecule has been further utilized for mono-dehalogenation under visible light irradiation and selective amide reduction. Moreover, the protocol has also been demonstrated on a gram scale.
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Affiliation(s)
- Vikas V Khade
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Pune, Maharashtra 411008, India
| | - Anindita Bhowmick
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Pune, Maharashtra 411008, India
| | - Archana S Thube
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Pune, Maharashtra 411008, India
| | - Ramakrishna G Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Pune, Maharashtra 411008, India
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4
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Dharpure PD, Behera M, Thube AS, Bhat RG. Base Dependent Rearrangement of Dithiane and Dithiolane under Visible-light Photoredox catalysis. Chem Asian J 2023; 18:e202201128. [PMID: 36630181 DOI: 10.1002/asia.202201128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 01/04/2023] [Accepted: 01/09/2023] [Indexed: 01/12/2023]
Abstract
The rearrangement of dithiolanes and dithianes to access disulfide-linked-dithioesters under visible-light photoredox catalysis via controlled C-S bond cleavage has been disclosed. Unlike, the usual deprotection of dithioacetals to corresponding aldehydes under the oxidative conditions, we observed unique regioselective oxidative reactivity of five and six membered cyclic dithioacetals to form disulfide-linked-dithioesters by exchanging DMAP and imidazole bases. The generality of the protocol has been demonstrated by exploring a wide range of substrates. As an application, in situ generated thiyl radical has been trapped with disulfides to prepare hetero-disulfides of potential utility. The protocol proved to be practical on gram scale quantity and relied on clean energy source for the transformation. Based on the series of control experiments, cyclic voltammetry and Stern-Volmer studies the plausible mechanism has been proposed.
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Affiliation(s)
- Pankaj D Dharpure
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
| | - Mousumi Behera
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
| | - Archana S Thube
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
| | - Ramakrishna G Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
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5
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Navale BS, Laha D, Banerjee S, Vanka K, Bhat RG. Highly Site-Selective Direct C-H Bond Functionalization of Unactivated Arenes with Propargyl α-Aryl-α-diazoacetates via Scandium Catalysis. J Org Chem 2022; 87:13583-13597. [PMID: 36181673 DOI: 10.1021/acs.joc.2c01185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Highly chemo- and regio-selective C-H bond functionalization of unactivated arenes with propargyl α-aryl-α-diazoacetates has been developed using scandium catalysis. A variety of unactivated, mildly deactivated, and electronically activated arenes have been functionalized using this protocol. The synergistic combination of scandium triflate as a catalyst and propargyl α-aryl-α-diazoacetate as a reagent played a pivotal role in the effective C-H bond functionalization of arenes without the assistance of any directing group or ligand. The practicality of the protocol has been demonstrated by the gram-scale synthesis of very useful α,α-diarylacetates including antispasmodic drug-adiphenine. Based on the experimental observations, labeling experiment, and density functional theory calculations, a plausible reaction mechanism has been outlined.
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Affiliation(s)
- Balu S Navale
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Pune, Maharashtra 411008, India
| | - Debasish Laha
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Pune, Maharashtra 411008, India
| | - Subhrashis Banerjee
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, Maharashtra 411008, India.,Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India
| | - Kumar Vanka
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, Maharashtra 411008, India.,Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India
| | - Ramakrishna G Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Pune, Maharashtra 411008, India
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6
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Dharpure PD, Behera M, Khade VV, Thube AS, Bhat RG. Direct Access to Thiocyano-Thioesters from Cyclic Thioacetals via Photoredox Catalysis: An Introduction of Two Functional Groups in One Pot. Org Lett 2022; 24:6919-6924. [PMID: 36121933 DOI: 10.1021/acs.orglett.2c02601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cyanation of organic compounds is an important synthetic transformation and mainly relies on a toxic CN source. Undeniably, thiocyanate salt has emerged as a very mild and environmentally benign CN source, yet its synthetic utility for cyanation is highly limited to very few types of organic compounds. Herein, we report the direct cyanation of cyclic thioacetals for accessing compounds with two different functional groups (thiocyano-thioesters) in one pot using sodium thiocyanate via photoredox catalysis. The protocol has been further extended for the direct cyanation of disulfides and diselenide to access aryl thiocyanates and aryl selenocyanate. A plausible mechanism has been proposed based on a series of control experiments, cyclic voltammetry and Stern-Volmer studies.
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Affiliation(s)
- Pankaj D Dharpure
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
| | - Mousumi Behera
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
| | - Vikas V Khade
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
| | - Archana S Thube
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
| | - Ramakrishna G Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India
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7
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Bhowmick A, Warghude PK, Bhat RG. Visible Light Promoted Metal‐Free Sustainable Reduction of α‐Alkylidene Oxindoles/Succinimides. ASIAN J ORG CHEM 2022. [DOI: 10.1002/ajoc.202200205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Anindita Bhowmick
- Indian Institute of Science Education and Research Pune Chemistry 411008 Pune INDIA
| | - Prakash K. Warghude
- Indian Institute of Science Education and Research Pune Chemistry 411008 PUNE INDIA
| | - Ramakrishna G. Bhat
- IISER Pune: Indian Institute of Science Education Research Pune Department of Chemistry C-Wing, Main Building, IISER-P 411008 Pune INDIA
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8
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Warghude PK, Bhowmick A, Bhat RG. Direct Access to Spirooxindole Dihydropyrrole Fused Pyrazolones and Bis-Spiropyrazolone Derivatives. Tetrahedron Lett 2022. [DOI: 10.1016/j.tetlet.2022.153791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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9
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Laha D, Meher KB, Bankar OS, Bhat RG. Silver‐Catalyzed One‐Pot Access to Diastereoselective Benzo[5,6]oxepino[2,3‐c]pyrroles via Formal (5+2)‐Annulation of Donor‐/Acceptor‐Type Aryl Vinyl diazosuccinimide with Ketones. ASIAN J ORG CHEM 2022. [DOI: 10.1002/ajoc.202200062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Debasish Laha
- IISER Pune: Indian Institute of Science Education Research Pune Department of Chemistry Dr. Homi Bhabha Rd., NCL colony, Pashan 411008 Pune INDIA
| | - Kajal B. Meher
- IISER Pune: Indian Institute of Science Education Research Pune Department of Chemistry 411008 Pune INDIA
| | - Onkar S. Bankar
- IISER Pune: Indian Institute of Science Education Research Pune Department of Chemistry 411008 Pune INDIA
| | - Ramakrishna G. Bhat
- IISER Pune: Indian Institute of Science Education Research Pune Department of Chemistry C-Wing, Main Building, IISER-P 411008 Pune INDIA
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10
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Khade VV, Thube AS, Dharpure PD, Bhat RG. Direct synthesis of 1,3-dithiolanes from terminal alkynes via visible light photoredox catalysis. Org Biomol Chem 2022; 20:1315-1319. [DOI: 10.1039/d1ob02154k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
AA visible light-mediated, metal-free, regioselective dihydrothionation of terminal aromatic as well as heteroaromatic alkynes has been achieved by using Eosin Y as a photoredox catalyst at room temperature. The protocol...
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11
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Bhowmick A, Warghude PK, Dharpure PD, Bhat RG. Direct access to α-acyloxycarbonyl compounds and esters via oxidative esterification of aldehydes under visible light. Org Chem Front 2021. [DOI: 10.1039/d1qo00731a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
An efficient synthesis of α-acyloxycarbonyl compounds and esters from aldehydes and α-bromocarbonyl compounds/benzyl bromide derivatives via photoredox catalysis has been developed.
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Affiliation(s)
- Anindita Bhowmick
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Maharashtra, India
| | - Prakash K. Warghude
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Maharashtra, India
| | - Pankaj D. Dharpure
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Maharashtra, India
| | - Ramakrishna G. Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pashan, 411008, Maharashtra, India
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12
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Warghude PK, Sabale AS, Dixit R, Vanka K, Bhat RG. An easy and practical approach to access multifunctional cylcopentadiene- and cyclopentene-spirooxindoles via [3 + 2] annulation. Org Biomol Chem 2021; 19:4338-4345. [PMID: 33908568 DOI: 10.1039/d1ob00514f] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A highly regioselective [3 + 2] annulation of Morita-Baylis-Hillman (MBH) carbonates of isatin with aurone/thioaurone is developed. Spiroheterocycles such as spirooxindole cyclopentadiene and spirooxindole fused hydroxy cyclopentene derivatives are constructed in one pot by exploring the reactivity of Lewis bases. Combined experimental and density functional theory (DFT) calculations offered an insight into the reaction mechanism.
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Affiliation(s)
- Prakash K Warghude
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr Homi Bhabha Road, Pashan, Pune, 411008, Maharashtra, India.
| | - Abhijeet S Sabale
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr Homi Bhabha Road, Pashan, Pune, 411008, Maharashtra, India.
| | - Ruchi Dixit
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr Homi Bhabha Road, Pune-411008, India and Academy of Scientific and Innovative Research (AcSIR), Ghaziabad - 201002, India
| | - Kumar Vanka
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr Homi Bhabha Road, Pune-411008, India and Academy of Scientific and Innovative Research (AcSIR), Ghaziabad - 201002, India
| | - Ramakrishna G Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr Homi Bhabha Road, Pashan, Pune, 411008, Maharashtra, India.
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13
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Reddy C, Shaikh JY, Bhat RG. Access to Hetero-Benzyl Scaffolds via Transient-Ligand-Enabled Direct γ-C(sp 3)-H Arylation of 3-Methylheteroarene-2-Carbaldehydes. J Org Chem 2020; 85:6924-6934. [PMID: 32348142 DOI: 10.1021/acs.joc.0c00154] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
An efficient and straightforward method has been developed for the synthesis of β-benzyl-substituted 5-membered heterocyclic carbaldehydes via transient directing-group-enabled direct γ-C(sp3)-H arylation of 3-methylheteroarene-2-carbaldehydes. A wide range of 3-methylheteroarene carbaldehydes undergo coupling with a variety of aryl iodides, including less reactive iodo pyridine derivatives to provide a library of highly selective functionalized products in good to excellent yields. Some of these products have been successfully utilized in synthesizing useful synthetic intermediates.
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Affiliation(s)
- Chennakesava Reddy
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr. Homi Bhabha Road, Pashan, 411008 Pune, Maharashtra, India
| | - Javed Y Shaikh
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr. Homi Bhabha Road, Pashan, 411008 Pune, Maharashtra, India
| | - Ramakrishna G Bhat
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr. Homi Bhabha Road, Pashan, 411008 Pune, Maharashtra, India
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14
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Laha D, Bhat RG. Silver‐Catalyzed Epoxidation of Aldehydes Using Donor‐/ Acceptor‐type Vinyl Diazosuccinimides to Access Spiro‐Pyrrolidinedioneoxiranes. ASIAN J ORG CHEM 2020. [DOI: 10.1002/ajoc.202000123] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Debasish Laha
- Department of ChemistryIndian Institute of Science Education and Research (IISER) Pune Dr. Homi Bhabha Road, Pashan Pune 411008 Maharashtra India
| | - Ramakrishna G. Bhat
- Department of ChemistryIndian Institute of Science Education and Research (IISER) Pune Dr. Homi Bhabha Road, Pashan Pune 411008 Maharashtra India
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15
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Warghude PK, Sabale AS, Bhat RG. Access to highly enantioselective and diastereoselective spirooxindole dihydrofuran fused pyrazolones. Org Biomol Chem 2020; 18:1794-1799. [DOI: 10.1039/d0ob00007h] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Access to highly enantioselective and diastereoselective spirooxindole dihydrofuran fused pyrazolones from MBH-carbonates and pyrazole 4,5-diones.
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Affiliation(s)
- Prakash K. Warghude
- Department of Chemistry
- Main Building
- Indian Institute of Science Education and Research (IISER)-Pune
- Pune
- India
| | - Abhijeet S. Sabale
- Department of Chemistry
- Main Building
- Indian Institute of Science Education and Research (IISER)-Pune
- Pune
- India
| | - Ramakrishna G. Bhat
- Department of Chemistry
- Main Building
- Indian Institute of Science Education and Research (IISER)-Pune
- Pune
- India
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16
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17
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Navale BS, Laha D, Bhat RG. Propargyl α-aryl-α-diazoacetates as robust reagents for the effective C H bond functionalization of 1,3-diketones via scandium catalysis. Tetrahedron Lett 2019. [DOI: 10.1016/j.tetlet.2019.06.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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18
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Khopade TM, Warghude PK, Sonawane AD, Bhat RG. Multicomponent synthesis of pyroglutamic acid derivatives via Knoevenagel-Michael-hydrolysis-lactamization-decarboxylation (KMHL-D) sequence. Org Biomol Chem 2019; 17:561-566. [PMID: 30574984 DOI: 10.1039/c8ob02473a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A novel and practical method for the synthesis of 3-substituted pyroglutamic acid derivatives is described. One pot multicomponent reaction of Meldrum's acid, aldehyde and Schiff's base followed an unprecedented chemoselective Knoevenagel-Michael-hydrolysis-lactamization domino sequence to afford 4-carboxy 3-substituted pyroglutamic acid derivatives under mild conditions. A carboxy intermediate formed appears to accelerate its own formation. The generality of the synthesis is exemplified by the use of a wide variety of aldehydes including enolizable aliphatic aldehydes, while substrates are stable under reaction conditions.
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Affiliation(s)
- Tushar M Khopade
- Department of Chemistry, Indian Institute of Science Education and Research (IISER)-Pune, Dr Homi Bhabha Road, Pashan, 411008, Pune, Maharashtra, India.
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19
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Khopade TM, Warghude PK, Mete TB, Bhat RG. Acyl/aroyl Meldrum’s acid as an enol surrogate for the direct organocatalytic synthesis of α,β-unsaturated ketones. Tetrahedron Lett 2019. [DOI: 10.1016/j.tetlet.2018.12.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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20
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Warghude PK, Dharpure PD, Bhat RG. Cycloaddition of isatin-derived MBH carbonates and 3-methyleneoxindoles to construct diastereoselective cyclopentenyl bis-spirooxindoles and cyclopropyl spirooxindoles: Catalyst controlled [3 + 2] and [2 + 1] annulations. Tetrahedron Lett 2018. [DOI: 10.1016/j.tetlet.2018.10.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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21
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Syamala LVB, Mete TB, Bhat RG. FeCl 3 ·6H 2 O-catalyzed selective conjugate reduction of alkylidene- β -keto esters and alkylidene-1,3-diketones. Tetrahedron Lett 2018. [DOI: 10.1016/j.tetlet.2018.07.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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22
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Affiliation(s)
- Trimbak B. Mete
- Department of ChemistryIndian Institute of Science Education and Research (IISER)-Pune, Main Building Dr. Homi Bhabha Road, Pashan, Pune 411008 Maharashtra India
| | - Debasish Laha
- Department of ChemistryIndian Institute of Science Education and Research (IISER)-Pune, Main Building Dr. Homi Bhabha Road, Pashan, Pune 411008 Maharashtra India
| | - Ramakrishna G. Bhat
- Department of ChemistryIndian Institute of Science Education and Research (IISER)-Pune, Main Building Dr. Homi Bhabha Road, Pashan, Pune 411008 Maharashtra India
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Khopade TM, Mete TB, Arora JS, Bhat RG. An Adverse Effect of Higher Catalyst Loading and Longer Reaction Time on Enantioselectivity in an Organocatalytic Multicomponent Reaction. Chemistry 2018; 24:6036-6040. [DOI: 10.1002/chem.201800278] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Indexed: 12/25/2022]
Affiliation(s)
- Tushar M. Khopade
- Indian Institution of Science Education and Research (IISER)-Pune, Pashan; Pune 411 008, Maharashtra India
| | - Trimbak B. Mete
- Indian Institution of Science Education and Research (IISER)-Pune, Pashan; Pune 411 008, Maharashtra India
| | - Jyotsna S. Arora
- Indian Institution of Science Education and Research (IISER)-Pune, Pashan; Pune 411 008, Maharashtra India
| | - Ramakrishna G. Bhat
- Indian Institution of Science Education and Research (IISER)-Pune, Pashan; Pune 411 008, Maharashtra India
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Khopade TM, Sonawane AD, Arora JS, Bhat RG. Direct Organocatalytic Multicomponent Synthesis of Enantiopure γ
-Butyrolactones via Tandem Knoevenagel-Michael-Lactonization Sequence. Adv Synth Catal 2017. [DOI: 10.1002/adsc.201701084] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Tushar M. Khopade
- Department of Chemistry; Indian Institute of Science Education and Research (IISER)-Pune; Dr. Homi Bhabha Road Pashan 411008, Pune, Maharashtra India
| | - Amol D. Sonawane
- Department of Chemistry; Indian Institute of Science Education and Research (IISER)-Pune; Dr. Homi Bhabha Road Pashan 411008, Pune, Maharashtra India
| | - Jyotsna S. Arora
- Department of Chemistry; Indian Institute of Science Education and Research (IISER)-Pune; Dr. Homi Bhabha Road Pashan 411008, Pune, Maharashtra India
| | - Ramakrishna G. Bhat
- Department of Chemistry; Indian Institute of Science Education and Research (IISER)-Pune; Dr. Homi Bhabha Road Pashan 411008, Pune, Maharashtra India
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Mete TB, Khopade TM, Bhat RG. Oxidative decarboxylation of arylacetic acids in water: One-pot transition-metal-free synthesis of aldehydes and ketones. Tetrahedron Lett 2017. [DOI: 10.1016/j.tetlet.2017.06.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Abstract
A mild and efficient chemoselective N-deacetylation using the Schwartz reagent at room temperature in rapid time is described. The mild and neutral conditions enable orthogonal N-deacetylation in the presence of some of the common protecting groups (viz. Boc, Fmoc, Cbz, Ts). The deprotection conditions did not induce any epimerization at the chiral amino centre.
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Affiliation(s)
- Prakash R Sultane
- Mendeleev Block, Department of Chemistry, Indian Institute of Science Education & Research (IISER), Pune, 411008, Maharashtra, India.
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Affiliation(s)
- Amar R. Mohite
- Mendeleev Block, Department of Chemistry, Indian Institute of Science Education & Research (IISER), Pune, 411008, Maharashtra, India
| | - Ramakrishna G. Bhat
- Mendeleev Block, Department of Chemistry, Indian Institute of Science Education & Research (IISER), Pune, 411008, Maharashtra, India
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Sultane PR, Bhat RG. Stereoselective Approach to cis-2,3-Disubstituted Piperidines via Reduction of N-Acyliminium Ion Intermediate: Enantioselective Synthesis of (+)-(2S,3S)-CP-99,994. J Org Chem 2012. [DOI: 10.1021/jo302181k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Prakash R. Sultane
- Mendeleev Block, Department
of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Maharashtra, 411008, India
| | - Ramakrishna G. Bhat
- Mendeleev Block, Department
of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Maharashtra, 411008, India
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Affiliation(s)
- Amar R. Mohite
- Department of Chemistry, Mendeleev Block, Indian Institute of Science Education and Research (IISER),
Pune, Maharashtra, 411008, India
| | - Ramakrishna G. Bhat
- Department of Chemistry, Mendeleev Block, Indian Institute of Science Education and Research (IISER),
Pune, Maharashtra, 411008, India
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Hong CX, Gallegly ME, Browne GT, Bhat RG, Richardson PA, Kong P. The avocado subgroup of Phytophthora citricola constitutes a distinct species, Phytophthora mengei sp. nov. Mycologia 2009; 101:833-40. [PMID: 19927748 DOI: 10.3852/08-214] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Isolates from avocado tree cankers have been recognized as a distinct subgroup within the P. citricola complex since 1974, both morphologically and molecularly (isozyme and amplified fragment length polymorphism [AFLP] analyses). This subgroup is formally separated from P. citricola after comparative DNA fingerprinting and sequence analyses of the ITS region, as well as by morphological examinations. This new taxon is homothallic, produces plerotic oospores with paragynous antheridia and noncaducous semipapillate sporangia. Morphologically it differs from other species of Waterhouse group III by producing many large bizarre-shaped sporangia and smaller oogonia with asymmetric capitate antheridia. It belongs to clade 2 and is phylogenetically closer to P. siskiyouensis, P. capsici and P. tropicalis than to P. citricola. P. mengei can be easily differentiated from its relatives in the same clade and other species of this morpho-group by DNA fingerprints and sequence analysis. This new taxon is named Phytophthora mengei sp. nov.
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Affiliation(s)
- C X Hong
- Virginia Polytechnic Institute and State University, Hampton Roads Agricultural Research and Extension Center, Department of Plant Pathology, Physiology and Weed Science, 1444 Diamond Springs Road, Virginia Beach, Virginia 23455, USA.
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Choubdar N, Bhat RG, Stubbs KA, Yuzwa S, Pinto BM. Synthesis of 2-amido, 2-amino, and 2-azido derivatives of the nitrogen analogue of the naturally occurring glycosidase inhibitor salacinol and their inhibitory activities against O-GlcNAcase and NagZ enzymes. Carbohydr Res 2008; 343:1766-77. [PMID: 18358456 DOI: 10.1016/j.carres.2008.02.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2008] [Revised: 02/28/2008] [Accepted: 02/29/2008] [Indexed: 10/22/2022]
Abstract
Seven 2-substituted derivatives of the nitrogen analogue of salacinol, a naturally occurring glycosidase inhibitor, were synthesized for structure-activity studies with hexosaminidase enzymes. The target zwitterionic compounds were synthesized by means of nucleophilic attack of the 2-azido-1,4-dideoxy-1,4-imino-D-arabinitol at the least hindered carbon atom of 2,4-O-benzylidene-L-erythritol-1,3-cyclic sulfate. Hydrogenation of the azido zwitterionic compound in methanol resulted in the reduction of the azide and subsequent methylation of the resulting amine in one pot. A similar reaction, with ethanol as the solvent, gave the N-ethyl derivative. The 2-amino analogues were finally obtained by the reduction of the azide function using triphenylphosphine. Acylation of the amine using acetic, propionic, or valeric anhydride afforded the corresponding 2-amido derivatives. Deprotection of the acylated, coupled products using 80% trifluoroacetic acid proceeded smoothly. Unlike their sulfonium ion counterparts, these compounds were stable and did not undergo ring opening. We also report the synthesis of the parent nitrogen heterocycles, N-Boc-1,2,4-trideoxy-2-amino-1,4-imino-D-arabinitol, and 1,2,4-trideoxy-2-acetamido-1,4-imino-D-arabinitol and its corresponding N-Boc protected compound. The 2-substituted analogues and the parent iminoalditol showed marginal activity (<33% at 250 microM) against human O-GlcNAcase and Vibrio cholerae NagZ enzymes.
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Affiliation(s)
- Niloufar Choubdar
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
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Bhat RG, Browne GT. Genetic Diversity in Populations of Phytophthora citricola Associated with Horticultural Crops in California. Plant Dis 2007; 91:1556-1563. [PMID: 30780613 DOI: 10.1094/pdis-91-12-1556] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
California populations of the plant pathogen Phytophthora citricola were examined for amplified fragment length polymorphism (AFLP), pathogenicity on almond, and sensitivity to mefenoxam. The characterizations of AFLP variation and mefenoxam sensitivity were based on 86 isolates (44 from almond, 11 from avocado, 3 from strawberry, 18 from walnut, and 10 from six other hosts). Cluster analysis of the AFLP data using the unweighted pair group method indicated a high level of genetic diversity among the isolates, and four main clusters were identified-one dominated by isolates from almond, another including all isolates from avocado, and two including isolates from several hosts other than avocado. Analysis of molecular variance revealed that 38.4 and 24.9% of the AFLP variation were associated with host and geographical factors, respectively. Of 24 isolates, including those from almond, avocado, strawberry, and walnut, 22 were aggressive on almond shoots; there was no evidence of host specificity. All but 1 of the 86 isolates grew at different rates on V8 juice medium amended with mefenoxam at 1 ppm, indicating partial tolerance to the fungicide. Isolates of P. citricola from California populations are genetically diverse, and much of the variation is associated with host and geography. These populations are all potentially pathogenic on almond and tolerant to mefenoxam.
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Affiliation(s)
- R G Bhat
- Department of Plant Pathology, University of California, Davis 95616
| | - G T Browne
- United States Department of Agriculture-Agricultural Research Service, CPGRU, Department of Plant Pathology, University of California, Davis 95616
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Bhat RG, Kumar NS, Pinto BM. Synthesis of phosphate derivatives related to the glycosidase inhibitor salacinol. Carbohydr Res 2007; 342:1934-42. [PMID: 17572396 DOI: 10.1016/j.carres.2007.05.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 05/23/2007] [Accepted: 05/25/2007] [Indexed: 10/23/2022]
Abstract
The syntheses of polyhydroxylated imino- and anhydro thio-alditol compounds related to the naturally occurring glycosidase inhibitor, salacinol, containing a phosphate group in the side chain are described. The compounds lack hydroxyl groups on the acyclic side chain and are prototypes of the exact salacinol analogue. The synthetic strategy relies on the Mitsunobu reaction of N- and S-hydroxyalkyl derivatives of 2,3,5-tri-O-benzyl-1,4-dideoxy-1,4-imino-D-arabinitol and 1,4-anhydro-2,3,5-tri-O-benzyl-1-thio-D-arabinitol with dibenzyl phosphate to yield the corresponding protected heteroalditol phosphates. Screening of these compounds against recombinant human maltase glucoamylase (MGA), a critical intestinal glucosidase involved in the processing of oligosaccharides of glucose into glucose itself, shows that they are not effective inhibitors of MGA and demonstrates the importance of the hydroxyl and/or sulfate substituents present on the side chain for effective inhibition. The attempted synthesis of the exact analogue of salacinol by opening of cyclic phosphates is also described.
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Affiliation(s)
- Ramakrishna G Bhat
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
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Bhat RG, Colowit PM, Tai TH, Aradhya MK, Browne GT. Genetic and Pathogenic Variation in Phytophthora cactorum Affecting Fruit and Nut Crops in California. Plant Dis 2006; 90:161-169. [PMID: 30786407 DOI: 10.1094/pd-90-0161] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Isolates of Phytophthora cactorum and 15 other species of Phytophthora were characterized according to their genomic DNA, pathogenicity, and sensitivity to mefenoxam. Amplified fragment length polymorphism (AFLP) analysis was completed for 132 isolates of P. cactorum (30 from almond, 86 from strawberry, 5 from walnut, and 11 from other hosts) and 22 isolates of 15 other Phytophthora spp. from various hosts. All 16 Phytophthora spp. were distinguishable by unique AFLP banding patterns. Cluster analysis of the AFLP data revealed high coefficients of genetic similarity (>0.9) among all California isolates of P. cactorum. Analysis of molecular variance indicated that, among all 132 isolates of P. cactorum, 30.8 and 24.5% of the AFLP variation was associated with hosts and geographical sources of isolates, respectively, whereas 15.0% of the variation was associated with isolate niche (i.e., an aerial plant part, portion of the root system, or soil). Among the 86 isolates of P. cactorum from strawberry, characterization by source in the production system (i.e., fruiting field or plant nursery) did not account for a significant proportion of the variation (0.6%, P = 0.204). In pathogenicity tests on strawberry plants (cv. Diamante) in a greenhouse, isolates of P. cactorum from hosts other than strawberry and an isolate from a strawberry fruit caused only negligible amounts of disease, but isolates from strawberry root systems were highly aggressive. On excised shoot segments of almond (cv. Drake), all isolates of P. cactorum originally from almond were pathogenic, and 8 of 17 isolates of the pathogen from other hosts caused significantly less disease than the almond isolates. All 132 isolates of P. cactorum were sensitive to mefenoxam at 1 ppm. Populations of P. cactorum in California apparently are mefenoxam sensitive and exhibit host specificity with relatively minor variation in genomic DNA. The genetic variation observed in P. cactorum included significant geographical and host origin components, which has implications for disease management approaches.
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Affiliation(s)
- R G Bhat
- Department of Plant Pathology, University of California, Davis 95616
| | - P M Colowit
- United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Crops Pathology and Genetics Research Unit (CPGRU), Department of Plant Sciences, University of California, Davis 95616
| | - T H Tai
- United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Crops Pathology and Genetics Research Unit (CPGRU), Department of Plant Sciences, University of California, Davis 95616
| | - M K Aradhya
- USDA-ARS National Clonal Germplasm Repository, University of California, Davis 95616
| | - G T Browne
- USDA-ARS, CPGRU, Department of Plant Pathology, University of California, Davis, CA 95616
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Koike ST, Browne GT, Bhat RG, Lee RCM, Tjosvold SA, Buermeyer K. Phytophthora Leaf Spot and Foliar Blight of Pieris japonica Caused by Phytophthora citricola in California. Plant Dis 2005; 89:1013. [PMID: 30786647 DOI: 10.1094/pd-89-1013b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
During 2004, containerized nursery stock of lily-of-the-valley-bush (Pieris japonica 'Flamingo', family Ericaceae) in Santa Cruz County was affected by a foliar disease. Symptoms consisted of large leaf spots, many developing at the leaf tips that ranged in size from 1 to greater than 4 cm in diameter. Spots were dark brown to almost black, generally oval to round, visible from both sides of the leaf, and did not exhibit signs of any pathogen. Lesions typically expanded and affected the entire leaf, leaf petiole, and stems, resulting in blight-like symptoms. Severely affected leaves abscised from the plant. In advanced stages of the disease, the foliage of the plant was killed. These symptoms resembled those caused by the sudden oak death (SOD) pathogen, Phytophthora ramorum (3). A Phytophthora sp. was isolated consistently from symptomatic leaf tissue. However, the species was identified as P. citricola based on morphological traits that included the following: production of semipapillate, noncaducous sporangia that were irregular in shape and occasionally had more than one apex; presence of oospores with paragynous antheridia in single culture; and radiate to slightly petaloid colony morphology (1). P. ramorum and other fungi were not recovered. Pathogenicity of four representative isolates was confirmed by gently abrading the adaxial surfaces of attached leaves with a sterile wire brush, placing a colonized agar plug (5 mm in diameter) on the surface, misting the leaf with sterile water, and then covering the plug with a plastic cap that was secured with a wire clip. Control leaves were treated in the same manner but received sterile agar plugs. Plants were maintained in a greenhouse at 23 to 25°C. After 2 days, all leaves inoculated with the isolates exhibited dark brown lesions and by day 6, lesions measured 3 cm in diameter. P. citricola was reisolated from symptomatic lesions. Sterile plug control leaves developed no symptoms. The test was repeated and the results were similar. To our knowledge, this is the first report of P. citricola causing a foliar disease of Pieris japonica in California. P. citricola has been reported as a pathogen on Pieris spp. in Ohio (2). Our finding is important because P. ramorum causes very similar symptoms on this same host (3). The occurrence of these two foliar Phytophthora spp. on this ornamental plant may complicate P. ramorum field detection during inspections and laboratory confirmations as established by quarantine regulations. References: (1) D. C. Erwin and O. K. Ribeiro. Morphology and Identification of Phytophthora Species. Pages 96-144 in: Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) W. W. P. Gerlach et al. Phytopathology 64:1368, 1974. (3) P. W. Tooley et al. Plant Dis. 88:993, 2004.
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Affiliation(s)
- S T Koike
- University of California Cooperative Extension, Salinas, 93901
| | - G T Browne
- USDA-ARS, Department of Plant Pathology, University of California, Davis, 95616
| | - R G Bhat
- USDA-ARS, Department of Plant Pathology, University of California, Davis, 95616
| | - R C M Lee
- USDA-ARS, Department of Plant Pathology, University of California, Davis, 95616
| | - S A Tjosvold
- University of California Cooperative Extension, Watsonville, 95076
| | - K Buermeyer
- University of California Cooperative Extension, Watsonville, 95076
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Ramesh R, Bhat RG, Chandrasekaran S. Highly Selective Deblocking of Propargyl Carbonates in the Presence of Propargyl Carbamates with Tetrathiomolybdate. J Org Chem 2005; 70:837-40. [PMID: 15675840 DOI: 10.1021/jo048777o] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Propargyloxycarbonyl chloride, 1, has been used to protect the hydroxyl and amino functionalities of amino alcohols and aminophenols in one pot using triethylamine or pyridine as a base. The increased reactivity of benzyltriethylammonium tetrathiomolybdate, 2, toward propargyl carbonates over propargyl carbamates is studied in detail and has been exploited further to develop an orthogonal protection strategy for the hydroxyl and amino functionalities. For example, 2-amino-1-butanol, 6a, was treated with 1 to get the N,O-diPoc compound 7a in 90% yield, which when treated with 1.1 equiv of 2 at room temperature removes the Poc group attached to oxygen while leaving the one attached to nitrogen intact to yield compound 8a in 85% yield. This particular observation offers a new protecting strategy where an amine and an alcohol group can be protected simultaneously in one pot, and in a later synthetic step, if the alcohol group has to be deprotected selectively, it can be achieved with 1 equiv of 2.
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Affiliation(s)
- R Ramesh
- Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, Karnataka, India
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Abstract
Polygalacturonic acid (PGA) is an important constituent of Sorensen's NP-10 medium (NP-10) for estimating the population density of Verticillium dahliae in soil. Different types of PGA are available, but not all of them favor the growth of V. dahliae. Unavailability of PGA sodium salt from orange (P-1879) has created an unprecedented problem for the quantification of microscle-rotia (MS) of V. dahliae in soil. The PGA from orange (P-3889) that is now available does not support the growth of V. dahliae. Therefore, experiments were conducted to optimize the use of NP-10 prepared with P-3889 and various concentrations of NaOH. NP-10 with P-3889 amended with eight concentrations of NaOH were compared with NP-10 prepared from PGA sodium salt from orange (P-1879, now discontinued) and citrus (P-3850) along with cellophane and Na-pectate media for recovery of MS from soil and growth of V. dahliae on the media. Seven soils were assayed for MS, and eight isolates of V. dahliae were evaluated for growth and production of MS. Concentrations of NaOH >0.035N and <0.02N in NP-10 with P-3889 reduced mycelial growth, microsclerotial production, and recovery of MS from soils. Similarly, NP-10 with P-3850 alone, cellophane, and Na-pectate media had significantly reduced growth on media and recovery of V. dahliae from soils. The NP-10 with P-3889 and 0.025N NaOH consistently yielded numbers of V. dahliae MS from soil samples and supported the growth and production of MS similar to the NP-10 with P-1879. The medium developed in this study can serve as a direct replacement for the original NP-10 that was developed nearly three decades ago, an important component of which is no longer available.
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Affiliation(s)
- Z Kabir
- Department of Plant Pathology, University of California-Davis, c/o United States Agricultural Research Station, Salinas 93905
| | - R G Bhat
- Department of Plant Pathology, University of California-Davis, c/o United States Agricultural Research Station, Salinas 93905
| | - K V Subbarao
- Department of Plant Pathology, University of California-Davis, c/o United States Agricultural Research Station, Salinas 93905
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Bhat RG, Porhiel E, Saravanan V, Chandrasekaran S. Utility of tetrathiomolybdate and tetraselenotungstate: efficient synthesis of cystine, selenocystine, and their higher homologues. Tetrahedron Lett 2003. [DOI: 10.1016/s0040-4039(03)01222-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
Epidemics of Verticillium wilt in pepper fields of the central coast of California and isolates of Verticillium dahliae associated with these epidemics were characterized. The mean incidence of wilted plants per field ranged from 6.3 to 97.8% in fields with Anaheim, jalapeno, paprika, or bell peppers. In general, incidence of wilt in jalapeno and bell pepper crops was lower than in crops of other types of pepper. Inoculum density of V. dahliae in the surveyed pepper fields ranged from 2.7 to 66.6 microsclerotia g-1 dry soil, and the correlation between disease incidence and density of microsclerotia was high (r = 0.81, P < 0.01). Distribution of Verticillium wilt was aggregated in a majority of the pepper fields surveyed, but the degree of aggregation varied. Vegetative compatibility group (VCG) characterization of 67 isolates of V. dahliae indicated that 67% belonged to VCG 2, 22% to VCG 4, and 11% to a new group, designated VCG 6. The pathogenicity of isolates of V. dahliae from bell pepper and tomato plants was tested by inoculating 1-month-old bell pepper (cv. Cal Wonder) and tomato (cv. EP 7) seedlings and incubating the inoculated plants in the greenhouse. Seedlings of bell pepper were susceptible only to the isolates of V. dahliae from pepper, whereas seedlings of tomato were susceptible to both pepper and tomato isolates. Pepper isolates belonging to VCG 2, VCG 4, and VCG 6 were highly pathogenic to bell pepper and chili pepper. Temperatures between 15 and 25°C were optimal for mycelial growth of a majority of isolates of V. dahliae. Molecular characterization of pepper isolates of V. dahliae using a polymerase chain reaction (PCR)-based random amplified polymorphic DNA (RAPD) technique revealed minor variation among these isolates, but unique polymorphic banding patterns were observed for isolates belonging to VCG 6. Verticillium wilt of pepper is a major production constraint in the central coast of California. More aggressive isolates of V. dahliae may have been selected in this region as a result of intensive cropping practices.
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Affiliation(s)
- R G Bhat
- Department of Plant Pathology, University of California, Davis, c/o U.S. Agricultural Research Station, Salinas, CA 93905
| | - R F Smith
- University of California Cooperative Extension, Salinas 93901
| | - S T Koike
- University of California Cooperative Extension, Salinas 93901
| | - B M Wu
- Department of Plant Pathology, University of California, Davis, c/o U.S. Agricultural Research Station, Salinas, CA 93905
| | - K V Subbarao
- Department of Plant Pathology, University of California, Davis, c/o U.S. Agricultural Research Station, Salinas, CA 93905
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Bhat RG, Sinha S, Chandrasekaran S. Propargyloxycarbonyl (Poc) amino acid chlorides as efficient coupling reagents for the synthesis of 100% diastereopure peptides and resin bound tetrathiomolybdate as an effective deblocking agent for the Poc group. Chem Commun (Camb) 2002:812-3. [PMID: 12122992 DOI: 10.1039/b200155a] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthesis of short peptides using propargyloxycarbonyl amino acid chlorides as effective coupling reagents and polymer supported tetrathiomolybdate as an efficient deblocking agent are reported.
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Affiliation(s)
- Ramakrishna G Bhat
- Department of Organic Chemistry, Indian Institute of Science, Bangalore-560 012, India
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Bhat RG, Kérourédan E, Porhiel E, Chandrasekaran S. Synthesis and applications of propargyl pentafluorophenyl carbonate for peptide synthesis. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(02)00287-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Abstract
Isolates of Verticillium dahliae from 15 different hosts and V. albo-atrum from alfalfa were tested for their ability to cause wilt on broccoli using a root-dip inoculation method. None of the isolates caused vascular discoloration in broccoli except those from cabbage and cauliflower that were weakly pathogenic. Broccoli cultivars Baccus, Greenbelt, Parasol, Patriot, and Symphony showed resistance to Verticillium infection. Re-isolated strains from fresh samples of internally discolored broccoli and cauliflower root tissues were unable to cause disease symptoms on re-inoculation of broccoli, but caused severe disease on cauliflower. Inoculation of 5-, 7-, 9-, or 11-week-old plants did not alter the resistance in broccoli or the susceptibility in cauliflower against Verticillium. Immunity of broccoli against infection by isolates of V. dahliae from non-crucifer hosts, its resistance against crucifer isolates, and as previously described, attrition of V. dahliae microsclerotia in soil by broccoli residue, coupled with its importance as a commercial vegetable, make broccoli an attractive rotation crop for the management of Verticillium wilt in many cropping systems.
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Affiliation(s)
- R G Bhat
- Department of Plant Pathology, University of California, Davis, c/o U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905
| | - K V Subbarao
- Department of Plant Pathology, University of California, Davis, c/o U.S. Agricultural Research Station, 1636 E. Alisal St., Salinas, CA 93905
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47
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Abstract
ABSTRACT Verticillium dahliae isolates from artichoke, bell pepper, cabbage, cauliflower, chili pepper, cotton, eggplant, lettuce, mint, potato, strawberry, tomato, and watermelon and V. albo-atrum from alfalfa were evaluated for their pathogenicity on all 14 hosts. One-month-old seedlings were inoculated with a spore suspension of about 10(7) conidia per ml using a root-dip technique and incubated in the greenhouse. Disease incidence and severity, plant height, and root and shoot dry weights were recorded 6 weeks after inoculation. Bell pepper, cabbage, cauliflower, cotton, eggplant, and mint isolates exhibited host specificity and differential pathogenicity on other hosts, whereas isolates from artichoke, lettuce, potato, strawberry, tomato, and watermelon did not. Bell pepper was resistant to all Verticillium isolates except isolates from bell pepper and eggplant. Thus, host specificity exists in some isolates of V. dahliae. The same isolates were characterized for vegetative compatibility groups (VCGs) through complementation of nitrate nonutilizing (nit) mutants. Cabbage and cauliflower isolates did not produce nit mutants. The isolate from cotton belonged to VCG 1; isolates from bell pepper, eggplant, potato, and tomato, to VCG 4; and the remaining isolates, to VCG 2. These isolates were also analyzed using the random amplified polymorphic DNA (RAPD) method. Forty random primers were screened, and eighteen of them amplified DNA from Verticillium. Based on RAPD banding patterns, cabbage and cauliflower isolates formed a unique group, distinct from other V. dahliae and V. albo-atrum groups. Minor genetic variations were observed among V. dahliae isolates from other hosts, regardless of whether they were host specific or not. There was no correlation among pathogenicity, VCGs, and RAPD banding patterns. Even though the isolates belonged to different VCGs, they shared similar RAPD profiles. These results suggest that management of Verticillium wilt in some crops through crop rotation is a distinct possibility.
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48
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Abstract
In mid-August 1998, artichoke (Cynara scolymus L.) plants of cultivar Imperial Star in a field in the Salinas area of the central coast of California developed wilt symptoms. The plants were stunted with chlorotic, drooping, and dried leaves near the bottom and middle of the plants as previously described in Italy (1). Diseased plants produced smaller edible buds and, in severe cases, buds were discolored with dried outer bracts. Roots exhibited the characteristic vascular discoloration of Verticillium infection. In one part of the infested field, artichoke was near harvest with 85% of plants showing wilt symptoms with vascular discoloration whereas the other part had a 60-day-old crop with 98% of plants infected. Yield in the field was reduced by as much as 50%. Verticillium dahliae was isolated from infected plant samples on NP-10 medium (2), and isolates were single spored before storing on potato dextrose agar at 4°C. Identity of the pathogen was confirmed based on colony morphology and formation of microsclerotia. In root-dip inoculation tests in the greenhouse, two V. dahliae isolates from artichoke infected 1-month-old artichoke seedlings that wilted within 6 weeks of inoculation. V. dahliae was reisolated from plants showing vascular discoloration. Cross-inoculation studies revealed that artichoke isolates caused a moderate level of disease in lettuce, but only a trace of vascular discoloration in cauliflower. Lettuce isolates caused a severe wilt in artichoke. Cauliflower isolates did not cause wilt in lettuce and caused only slight vascular discoloration in artichoke. This is the first report of a Verticillium wilt of artichoke in California. References: (1) M. Cirulli et al. Plant Dis. 78:680, 1994. (2) L. H. Sorensen et al. Phytopathology 81:1347, 1991.
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Affiliation(s)
- R G Bhat
- Department of Plant Pathology, University of California, Davis, 1636 E. Alisal St., Salinas, CA 93905
| | - K V Subbarao
- Department of Plant Pathology, University of California, Davis, 1636 E. Alisal St., Salinas, CA 93905
| | - M A Bari
- Artichoke Research Association, 1636 E. Alisal St., Salinas, CA 93905
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49
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Mukhopadhyay T, Nadkarni SR, Bhat RG, Gupte SV, Ganguli BN, Petry S, Kogler H. Mathemycin B, a new antifungal macrolactone from actinomycete species HIL Y-8620959. J Nat Prod 1999; 62:889-890. [PMID: 10395510 DOI: 10.1021/np980369q] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A new macrocyclic lactone antibiotic mathemycin B (1) was isolated from the fermentation broth of an Actinomycete sp. culture Y-8620959. The structure of 1 was elucidated by high-resolution MS and interpretation of 2D NMR results. Mathemycin B is active against a variety of phytopathogenic organisms.
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Affiliation(s)
- T Mukhopadhyay
- Research Centre, Hoechst Marion Roussel Ltd., Mulund (W), Mumbai 400 080, India.
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50
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Nadkarni SR, Mukhopadhyay T, Bhat RG, Gupte SV, Sachse B. Mathemycin A, a new antifungal macrolactone from Actinomycete sp. HIL Y-8620959. I. Fermentation, isolation, physico-chemical properties and biological activities. J Antibiot (Tokyo) 1998; 51:579-81. [PMID: 9711221 DOI: 10.7164/antibiotics.51.579] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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