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Journal of Chemical Sciences

, Volume 116, Issue 3, pp 159–162 | Cite as

Proline-catalysed asymmetric ketol cyclizations: The template mechanism revisited

  • R. Malathi
  • D. Rajagopal
  • Zoltan G. Hajos
  • S. Swaminathan
Article

Abstract

A modified template mechanism based on modelling studies of energy minimised complexes is presented for the asymmetric proline-catalysed cyclization of triketones1,2 and3 to the 2S,3S-ketols1a,2a and3a respectively. The template model involves a three-point contact as favoured in enzyme-substrate interactions. Our minimisation studies are in agreement with the divergent behaviour of the 6,5-, 6,6-and 6,7-bicyclic systems. They support the high 93.4%ee observed with the 6,5-bicyclic ketol and the lower 73%ee found with the 6,6-bicyclic ketol. The calculations also explain the lack of asymmetric induction with the 6,7-bicyclic system

Keywords

Proline-catalysed ketol cyclization template mechanism 

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References

  1. 1.
    Movassaghi M and Jacobsen E N 2002Science 298 1904CrossRefGoogle Scholar
  2. 2.
    Hajos Z G and Parrish D R 1974J. Org. Chem. 39 1615CrossRefGoogle Scholar
  3. 3.
    Hajos Z G and Parrish DR 1971German Patent DE 2102623Google Scholar
  4. 4.
    Eder U, Sauer G and Wiechert R 1971Angew. Chem., Int. Ed. (Engl.) 10 496CrossRefGoogle Scholar
  5. 5.
    List B, Lerner R A and Barbas C F III 2000J. Am. Chem. Soc. 122 2395CrossRefGoogle Scholar
  6. 6.
    List B 2002J. Am. Chem. Soc. 124 5656, and earlier papers cited thereinCrossRefGoogle Scholar
  7. 7.
    List B 2002Tetrahedron 58 5573CrossRefGoogle Scholar
  8. 8.
    Northrup A B and MacMillan D W C 2002J. Am. Chem. Soc. 124 6798CrossRefGoogle Scholar
  9. 9.
    Agami C, Puchot C and Sevestre H 1986Tetrahedron Lett. 27 1501CrossRefGoogle Scholar
  10. 10.
    Hoang L, Bahmanyar S, Houk K N and List B 2003J. Am. Chem. Soc. 125 16CrossRefGoogle Scholar
  11. 11.
    Hajos Z 2002 http://preprint.chemweb.com/orgchem/ 0209001, Sept 5Google Scholar
  12. 12.
    Rajagopal D, Moni M S, Subramanian S and Swaminathan S 1999Tetrahedron: Asymmetry 10 1631CrossRefGoogle Scholar
  13. 13.
    Shamala N, Row T N G and Venkatesan K 1976Acta Crystallogr. B32 3267Google Scholar
  14. 14.
    Rajagopal D 1999PhD Studies in asymmetric syntheses, thesis, University of Madras, ChennaiGoogle Scholar
  15. 15.
    Florkin M and Statz G (eds) 1964 InComprehensive biochemistry 12 237Google Scholar

Copyright information

© Indian Academy of Sciences 2004

Authors and Affiliations

  • R. Malathi
    • 1
  • D. Rajagopal
    • 2
  • Zoltan G. Hajos
    • 3
  • S. Swaminathan
    • 2
  1. 1.Department of Crystallography and BiophysicsUniversity of MadrasChennaiIndia
  2. 2.Department of Organic ChemistryUniversity of MadrasChennaiIndia
  3. 3.Hoffmann-La Roche IncNutleyUSA

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