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Hong AY, Stoltz BM. The Construction of All-Carbon Quaternary Stereocenters by Use of Pd-Catalyzed Asymmetric Allylic Alkylation Reactions in Total Synthesis. European J Org Chem 2013; 2013:2745-2759. [PMID: 24944521 PMCID: PMC4059687 DOI: 10.1002/ejoc.201201761] [Citation(s) in RCA: 292] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2012] [Indexed: 11/08/2022]
Abstract
All-carbon quaternary stereocenters have posed significant challenges in the synthesis of complex natural products. These important structural motifs have inspired the development of broadly applicable palladium-catalyzed asymmetric allylic alkylation reactions of unstabilized non-biased enolates for the synthesis of enantioenriched α-quaternary products. This microreview outlines key considerations in the application of palladium-catalyzed asymmetric allylic alkylation reactions and presents recent total syntheses of complex natural products that have employed these powerful transformations for the direct, catalytic, enantioselective construction of all-carbon quaternary stereocenters.
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Affiliation(s)
- Allen Y. Hong
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125, USA, Homepage: http://stoltz.caltech.edu
| | - Brian M. Stoltz
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125, USA, Homepage: http://stoltz.caltech.edu
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5
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Behenna DC, Mohr JT, Sherden NH, Marinescu SC, Harned AM, Tani K, Seto M, Ma S, Novák Z, Krout MR, McFadden RM, Roizen JL, Enquist JA, White DE, Levine SR, Petrova KV, Iwashita A, Virgil SC, Stoltz BM. Enantioselective decarboxylative alkylation reactions: catalyst development, substrate scope, and mechanistic studies. Chemistry 2011; 17:14199-223. [PMID: 22083969 PMCID: PMC3365686 DOI: 10.1002/chem.201003383] [Citation(s) in RCA: 172] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 07/29/2011] [Indexed: 11/07/2022]
Abstract
α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursor: enol carbonates, enol silanes, and racemic β-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity. Catalyst discovery and development, the optimization of reaction conditions, the exploration of reaction scope, and applications in target-directed synthesis are reported. Experimental observations suggest that these alkylation reactions occur through an unusual inner-sphere mechanism involving binding of the prochiral enolate nucleophile directly to the palladium center.
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Affiliation(s)
| | | | - Nathaniel H. Sherden
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Smaranda C. Marinescu
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Andrew M. Harned
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Kousuke Tani
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Masaki Seto
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Sandy Ma
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Zoltán Novák
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Michael R. Krout
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Ryan M. McFadden
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Jennifer L. Roizen
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - John A. Enquist
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - David E. White
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Samantha R. Levine
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Krastina V. Petrova
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Akihiko Iwashita
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Scott C. Virgil
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
| | - Brian M. Stoltz
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 101-20, Pasadena, CA 91125 (USA)
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Tiefenbacher K, Gollner A, Mulzer J. Syntheses and antibacterial properties of iso-platencin, Cl-iso-platencin and Cl-platencin: identification of a new lead structure. Chemistry 2010; 16:9616-22. [PMID: 20486112 DOI: 10.1002/chem.201000706] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Platencin is a novel antibiotic which is active against multiresistant pathogens. We describe efficient syntheses of three platencin analogues of varying activities which allow further conclusions about the pharmacophoric part of the molecule. The unnatural antibiotic iso-platencin, which is about as active as natural platencin, but much more selective, was identified as a new lead structure.
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Affiliation(s)
- Konrad Tiefenbacher
- University of Vienna, Institute of Organic Chemistry, Währingerstrasse 38, 1090 Wien, Austria
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Palanichamy K, Kaliappan KP. Discovery and syntheses of "superbug challengers"-platensimycin and platencin. Chem Asian J 2010; 5:668-703. [PMID: 20209576 DOI: 10.1002/asia.200900423] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Bacteria have developed resistance to almost all existing antibiotics known today and this has been a major issue over the last few decades. The search for a new class of antibiotics with a new mode of action to fight these multiply-drug-resistant strains, or "superbugs", allowed a team of scientists at Merck to discover two novel antibiotics, platensimycin and platencin using advanced screening strategies, as inhibitors of bacterial fatty acid biosynthesis, which is essential for the survival of bacteria. Though both these antibiotics are structurally related, they work by slightly different mechanisms and target different enzymes conserved in the bacterial fatty acid biosynthesis. This Focus Review summarizes the synthetic and biological aspects of these natural products and their analogues and congeners.
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Affiliation(s)
- Kalanidhi Palanichamy
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400 076, India
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