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Organocatalytic asymmetric assembly reactions for the syntheses of carbohydrate derivatives by intermolecular michael-henry reactions

Academic Article
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Overview

authors

  • Uehara, H.
  • Imashiro, R.
  • Hernandez-Torres, G.
  • Barbas III, Carlos

publication date

  • November 2010

journal

  • Proceedings of the National Academy of Sciences of the United States of America  Journal

abstract

  • Given the significance of carbohydrates in life, medicine, and industry, the development of simple and efficient de novo methods to synthesize carbohydrates are highly desirable. Organocatalytic asymmetric assembly reactions are powerful tools to rapidly construct molecules with stereochemical complexity from simple precursors. Here, we present a simple and robust methodology for the asymmetric synthesis of pyranose derivatives with talo- and manno- configurations from simple achiral precursors through organocatalytic asymmetric intermolecular Michael-Henry reaction sequences. In this process, (tert-butyldimethylsilyloxy)acetaldehyde 1 was successfully utilized in two ways: as a donor in a highly selective anti-Michael reaction and as an acceptor in a consecutive Henry reaction. Varied nitroolefins served as Michael acceptors and varied aldehydes substituted for 1 as Henry acceptors providing for the construction of a wide range of carbohydrates with up to 5 stereocenters. In these reactions, a catalyst-controlled Michael reaction followed by a substrate-controlled Henry reaction provided 3,4-dideoxytalose derivatives 6 in a highly stereoselective manner. The Henry reaction was affected by addition of a simple base such as triethylamine: A complex chiral base was not necessary. 3,4-Dideoxymannose derivatives 7 were produced by simply changing the base from triethylamine to 1,8-diazabicyclo[5.4.0]undec-7-ene. Extension of this methodology to a syn-Michael initiated sequence was also successful. A mechanistic discussion is provided to explain the unusual substrate-induced stereoselectivity of the Henry reaction.

subject areas

  • Carbohydrates
  • Catalysis
  • Crystallography, X-Ray
  • Lactones
  • Mannose
  • Models, Chemical
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Research

keywords

  • Michael reaction
  • amine-thiourea catalyst
  • asymmetric reaction
  • carbohydrates
  • organocatalysis
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Identity

PubMed Central ID

  • PMC2996423

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.1003350107

PubMed ID

  • 20639468
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Additional Document Info

start page

  • 20672

end page

  • 20677

volume

  • 107

issue

  • 48

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