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Zard SZ. The xanthate route to six-membered carbocycles. JOURNAL OF CHEMICAL RESEARCH 2022. [DOI: 10.1177/17475198221088194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Convergent routes to various six-membered carbocyclic architectures exploiting the unique radical chemistry of xanthates are described in this brief review. Three approaches are discussed. The first is the modification of existing cyclohexane building blocks, namely, cyclohexanones, cyclohexenones and cyclohexenes. The second deals with the construction of six-membered carbocycles by associating the chemistry of xanthates with classical ionic reactions, especially the Robinson annulation, the Michael addition and the Horner–Wadsworth–Emmons condensation. Finally, the third route is the formation of six-membered rings by direct six- exo and, but more rarely, six- endo cyclisation modes. Many of the complex structures presented herein would be tedious to obtain by more traditional methods.
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Affiliation(s)
- Samir Z Zard
- Laboratoire de Synthèse Organique associé au C. N. R. S., UMR 7652, Ecole Polytechnique, Palaiseau, France
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Affiliation(s)
- Samir Z. Zard
- Laboratoire de Synthèse Organique, CNRS UMR 7652Ecole Polytechnique FR-91128 Palaiseau France
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Trubitsyn G, Nguyen VN, Di Tommaso C, Borchard G, Gurny R, Möller M. Impact of covalently Nile Red and covalently Rhodamine labeled fluorescent polymer micelles for the improved imaging of the respective drug delivery system. Eur J Pharm Biopharm 2019; 142:480-487. [PMID: 31336183 DOI: 10.1016/j.ejpb.2019.07.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Revised: 07/16/2019] [Accepted: 07/19/2019] [Indexed: 11/16/2022]
Abstract
Novel fluorescently labeled poly(ethylene glycol)-poly(hydroxyoctanoic acid) (MPEG-PHOA) block-copolymers were synthesized for the improved visualization of the deriving polymeric micelle drug delivery system. Albeit commonly used, one has to be aware that by simple incorporation of Nile Red (hydrophobic) or Rhodamine B (hydrophilic) as fluorescent compounds in nanocarriers (e.g., nanoparticles, liposomes or micelles) for imaging applications, these fluorescent probes can diffuse out of the carrier system and lead to artefacts due to the concomitant fluorescence loss or areal distribution. In order to inhibit such an uncontrolled diffusion, the Nile Red derivative 2-((9-(diethylamino)-5-oxo-5H-benzo[a]phenoxazin-2-yl)oxy)acetic acid was synthesized and covalently attached to the MPEG-PHOA block-copolymer via a mild Mitsunobu reaction to yield the desired MPEG-PHOA-Nile Red polymer for micelle preparations. Rhodamine B was coupled via its native carboxylic acid group with the copolymer MPEG-PHOA under mild conditions using DMAP, EDC, and NHS. For the proof of concept, aqueous solutions of composite micelles made of 0.5% (w/w fluorescence dye) MPEG-PHOA-dye and MPEG-PHOA copolymers were prepared ("spiking" of the non-labeled base MPEG-PHOA micelles) and characterized by transmission electron microscopy (TEM), dialysis and fluorescence spectrometry. The fluorescence intensity of the Nile Red in the solutions was followed up at physiological temperatures and pH values (37 °C, pH = 7.4 PBS buffer 0.01 M) over a period of 8 weeks. The labeled and non-labeled micelle formulations were tested in vitro in cells (Rhodamine-micelle formulations), then in vivo in a case study of an ophthalmic application (Nile Red micelle formulations). Both in vitro and in vivo experiments revealed a significant improvement of fluorescence stability of the MPEG-PHOA-dye formulations, facilitating the investigations on tracing the micelles and their stability. The results clearly demonstrate the value of the novel Nile Red and Rhodamine derivatives, whose simple synthesis and covalent attachment may easily be transferred to other nanosized polymeric drug delivery systems, e.g., MPEGylated or non-MPEGylated PLA/PLGA nanoparticles and be envisioned for novel theranostic systems.
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Affiliation(s)
- Gregory Trubitsyn
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, 1 Rue Michel Servet, CH-1206 Geneva, Switzerland
| | - Van Nga Nguyen
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, 1 Rue Michel Servet, CH-1206 Geneva, Switzerland
| | - Claudia Di Tommaso
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, 1 Rue Michel Servet, CH-1206 Geneva, Switzerland
| | - Gerrit Borchard
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, 1 Rue Michel Servet, CH-1206 Geneva, Switzerland.
| | - Robert Gurny
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, 1 Rue Michel Servet, CH-1206 Geneva, Switzerland
| | - Michael Möller
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, 1 Rue Michel Servet, CH-1206 Geneva, Switzerland
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Abstract
The alkylation of enolates is one of the backbones of ketone chemistry, yet in practice it suffers from numerous limitations due to problems of regiochemistry (including O- versus C-alkylation), multiple alkylations, self-condensation, competing elimination, and incompatibility with many polar groups that have to be protected. Over the years, various solutions have been devised to overcome these difficulties, such as the employment of auxiliary ester or sulfone groups to modify the p Ka of the enolizable hydrogens, the passage by the corresponding hydrazones, the use of transition-metal-catalyzed redox systems to formally alkylate ketones with alcohols, etc. Most of these hurdles disappear upon switching to α-ketonyl radicals. Radicals are tolerant of most polar functions, and radical additions to flat sp2 centers are generally easier to accomplish than enolate substitution at tetrahedral sp3 carbons. The main stumbling block, however, has been a lack of generally applicable methods for the generation and intermolecular capture of α-ketonyl radicals. We have found over the past years that the degenerative exchange of xanthates represents in many ways an ideal solution to this problem. It overcomes essentially all of the difficulties faced by other radical processes because of its unique ability to reversibly store reactive radicals in a dormant, nonreactive form. The lifetime of the radicals can therefore be significantly enhanced, even in the concentrated medium needed for bimolecular additions, while at the same time regulating their absolute and relative concentrations. The ability to perform intermolecular additions to highly functionalized alkene partners opens up numerous possibilities for rapid and convergent access to complex structures. Of particular importance is the elaboration of ketones that are prone to self-condensation, such trifluoroacetone, and of base-sensitive ketones, such as chloro- and dichloroacetone, since the products can be used for the synthesis of a myriad fluorinated and heteroaromatic compounds of relevance to medicinal chemistry and agrochemistry. The formal distal dialkylation of ketones, also of utmost synthetic interest, is readily accomplished, allowing convenient access to a wide array of useful ketone building blocks. Cascade processes can be implemented and, in alliance with powerful classical reactions (aldol, alkylative Birch reductions, etc.), furnish a quick route to complex polycyclic scaffolds. Furthermore, the presence of the xanthate group in the adducts can be exploited to obtain a variety of arenes and heteroarenes, such as pyrroles, thiophenes, naphthalenes, and pyridines, as well as enones, dienes, and cyclopropanes. Last but not least, the reagents and most of the starting materials are exceedingly cheap, and the reactions are safe and easy to scale up.
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Affiliation(s)
- Samir Z. Zard
- Laboratoire de Synthèse Organique, CNRS UMR 7652 Ecole Polytechnique, 91128 Palaiseau Cedex, France
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Quiclet-Sire B, Zard SZ. Some aspects of radical cascade and relay reactions. Proc Math Phys Eng Sci 2017; 473:20160859. [PMID: 28484329 PMCID: PMC5415689 DOI: 10.1098/rspa.2016.0859] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 03/02/2017] [Indexed: 01/28/2023] Open
Abstract
The ability to create carbon-carbon bonds is at the heart of organic synthesis. Radical processes are particularly apt at creating such bonds, especially in cascade or relay sequences where more than one bond is formed, allowing for a rapid assembly of complex structures. In the present brief overview, examples taken from the authors' laboratory will serve to illustrate the strategic impact of radical-based approaches on synthetic planning. Transformations involving nitrogen-centred radicals, electron transfer from metallic nickel and the reversible degenerative exchange of xanthates will be presented and discussed. The last method has proved to be a particularly powerful tool for the intermolecular creation of carbon-carbon bonds by radical additions even to unactivated alkenes. Various functional groups can be brought into the same molecule in a convergent manner and made to react together in order to further increase the structural complexity. One important benefit of this chemistry is the so-called RAFT/MADIX technology for the manufacture of block copolymers of almost any desired architecture.
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Affiliation(s)
| | - Samir Z. Zard
- Laboratoire de Synthèse Organique, CNRS UMR 7652, Ecole Polytechnique, 91128 Palaiseau, France
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Mikhaylov AA, Zard SZ. Extension to the Silyl-Tethered Radical Cyclization: Cyclohex-2-en-1-oxy Vinyl Silanes in Stereoselective Radical Addition/Cyclization Cascades. Org Lett 2017; 19:1866-1869. [PMID: 28358488 DOI: 10.1021/acs.orglett.7b00627] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel radical cascade reaction of xanthates with 1-[(vinyldimethylsilyl)oxy]cyclohex-2-enes is developed. Due to the steric and electronic differentiation of the two olefinic functions, exclusive regioselectivity and high stereoselectivity of the addition-cyclization are observed. Several methods for modification of both the silicon tether and the xanthate function are reported.
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Affiliation(s)
- Andrey A Mikhaylov
- Laboratoire de Synthèse Organique, CNRS UMR 7652 Ecole Polytechnique , Palaiseau 91128 Cedex, France
| | - Samir Z Zard
- Laboratoire de Synthèse Organique, CNRS UMR 7652 Ecole Polytechnique , Palaiseau 91128 Cedex, France
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Quiclet-Sire B, Zard SZ. On the Strategic Impact of the Degenerative Transfer of Xanthates on Synthetic Planning. Isr J Chem 2016. [DOI: 10.1002/ijch.201600094] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Béatrice Quiclet-Sire
- Laboratoire de Synthèse Organique associé au CNRS; Ecole Polytechnique, F-; 91128 Palaiseau Cedex France
| | - Samir Z. Zard
- Laboratoire de Synthèse Organique associé au CNRS; Ecole Polytechnique, F-; 91128 Palaiseau Cedex France
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Simeonov SP, Nunes JPM, Guerra K, Kurteva VB, Afonso CAM. Synthesis of Chiral Cyclopentenones. Chem Rev 2016; 116:5744-893. [DOI: 10.1021/cr500504w] [Citation(s) in RCA: 159] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Svilen P. Simeonov
- Institute
of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev str, bl.9, 1113 Sofia, Bulgaria
| | - João P. M. Nunes
- Department
of Chemistry, University College London, London WC1H 0AJ, United Kingdom
| | - Krassimira Guerra
- Research
Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Vanya B. Kurteva
- Institute
of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev str, bl.9, 1113 Sofia, Bulgaria
| | - Carlos A. M. Afonso
- Research
Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
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Goh KKK, Kim S, Zard SZ. Free-Radical Variant for the Synthesis of Functionalized 1,5-Diketones. Org Lett 2013; 15:4818-21. [DOI: 10.1021/ol402213k] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Kelvin Kau Kiat Goh
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore, and Laboratoire de Synthèse Organique, CNRS UMR 7652 Ecole Polytechnique, 91128 Palaiseau Cedex, France
| | - Sunggak Kim
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore, and Laboratoire de Synthèse Organique, CNRS UMR 7652 Ecole Polytechnique, 91128 Palaiseau Cedex, France
| | - Samir Z. Zard
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore, and Laboratoire de Synthèse Organique, CNRS UMR 7652 Ecole Polytechnique, 91128 Palaiseau Cedex, France
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Quiclet-Sire B, Zard SZ. Some aspects of radical chemistry in the assembly of complex molecular architectures. Beilstein J Org Chem 2013; 9:557-76. [PMID: 23616797 PMCID: PMC3629037 DOI: 10.3762/bjoc.9.61] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 02/25/2013] [Indexed: 11/23/2022] Open
Abstract
This review article describes briefly some of the radical processes developed in the authors' laboratory as they pertain to the concise assembly of complex molecular scaffolds. The emphasis is placed on the use of nitrogen-centred radicals, on the degenerate addition-transfer of xanthates, especially on its potential for intermolecular carbon-carbon bond formation, and on the generation and capture of radicals through electron transfer processes.
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Affiliation(s)
- Béatrice Quiclet-Sire
- Laboratoire de Synthèse Organique, CNRS UMR 7652, Ecole Polytechnique, 91128 Palaiseau, France
| | - Samir Z Zard
- Laboratoire de Synthèse Organique, CNRS UMR 7652, Ecole Polytechnique, 91128 Palaiseau, France
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Samanta S, Yasmin N, Kundu D, Ray JK. Thiol-mediated tandem Michael–aldol reaction: a convenient method for the synthesis of fused cyclopentenones. Tetrahedron Lett 2010. [DOI: 10.1016/j.tetlet.2010.05.142] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Quiclet-Sire B, Zard SZ. Powerful CarbonCarbon Bond Forming Reactions Based on a Novel Radical Exchange Process. Chemistry 2006; 12:6002-16. [PMID: 16791885 DOI: 10.1002/chem.200600510] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Xanthates and related derivatives have proved to be extremely useful for both inter- and intramolecular radical additions. The broad applicability of the intermolecular addition to un-activated olefins opens tremendous opportunities for synthesis, since various functional groups can be brought together under mild conditions and complex structures can be rapidly assembled. The presence of the xanthate in the product is also a powerful asset for further modifications, by both radical and non-radical pathways. Of special importance is the access to highly substituted aromatic and heteroaromatic derivatives and the synthesis of block polymers through a controlled radical polymerisation mediated by various thiocarbonylthio group containing agents (RAFT and MADIX processes).
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Affiliation(s)
- Béatrice Quiclet-Sire
- Laboratoire de Synthèse Organique associé au CNRS (UMR 7652), Département de Chimie, Ecole Polytechnique, 91128 Palaiseau, France
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Chapelon AS, Ollivier C, Santelli M. A short and convenient access to a trans-hydrindane unit from the anti-meso-acetylmethyldivinylcyclopentane via a radical pathway. Tetrahedron Lett 2006. [DOI: 10.1016/j.tetlet.2006.02.076] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Gómez G, Rivera H, García I, Estévez L, Fall Y. The furan approach to carbocyclic systems. Synthesis of cyclohexane derivatives from butenolides through an intramolecular Michael addition. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.06.137] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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