Total synthesis and structural elucidation of ent-micropyrone and (+)-ascosalipyrone

Org Biomol Chem. 2012 Aug 28;10(32):6547-53. doi: 10.1039/c2ob25501d. Epub 2012 Jul 3.

Abstract

The total synthesis of 6-[(1S,3S)-1,3-dimethyl-2-oxopentyl]-4-hydroxy-3,5-dimethyl-2H-pyran-2-one (22), the enantiomer of the natural product micropyrone (1), was achieved in 9 linear steps (10% overall yield), from Evans auxiliary (R)-12 with key coupling of the dianion of dione 17 and aldehyde 11. Formation of the pyrone ring and subsequent oxidation at C7 was achieved without epimerization of the sensitive position α to both the pyrone ring and the carbonyl. The same sequence using the alternate dione 24 achieved the total synthesis of 6-[(1S,3S)-1,3-dimethyl-2-oxopentyl]-4-hydroxy-3-methyl-2H-pyran-2-one (28), the (+)-enantiomer of the natural product, ascosalipyrone (2). In both cases diastereomeric aldehydes 11 and 16 were taken through the synthetic sequence to give two possible diastereomers of the natural products. Comparison of the (1)H and (13)C NMR data for the synthetic isomers with that reported for the natural products determined their relative stereochemistry. Comparison of the optical rotation obtained for 22 established it to be the enantiomer of micropyrone.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chemistry Techniques, Synthetic*
  • Crystallography, X-Ray
  • Isomerism
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Structure
  • Pyrones / chemical synthesis*
  • Pyrones / chemistry

Substances

  • Pyrones
  • ascosalipyrone
  • micropyrone