Chuktabularins E-T, 16-Norphragmalin Limonoids from Chukrasia tabularis var. velutina

J Nat Prod. 2010 May 28;73(5):835-43. doi: 10.1021/np900734c.

Abstract

Chuktabularins E-T (1-16), 16 new 16-norphragmalin limonoids, together with four known compounds, chuktabularins A-D, were isolated from the stem bark of Chukrasia tabularis var. velutina. These compounds possess a biosynthetically extended propionyl or acetyl group at C-15 and a characteristic ketal moiety between the limonoid skeleton and the acyl substituent at C-15. The structures of these compounds were established on the basis of detailed spectroscopic analysis, and that of 1 was confirmed by a single-crystal X-ray diffraction experiment, representing the first verification of the skeleton of 16-norphragmalin limonoids. Chuktabularins K-O (7-11) were found to be the first 19-acetoxylated 16-norphragmalin limonoids. Variable-temperature (1)H NMR experiments suggested that 7 exists as an equilibrium mixture of conformational isomers in solution. The absolute configuration of 5 was determined by the CD exciton chirality method on its 11,12-di-p-chlorobenzoate (5a), and those of 1-4 and 6-16 were proposed by correlating with 5 spectroscopically and biogenetically.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Drugs, Chinese Herbal / chemistry*
  • Drugs, Chinese Herbal / isolation & purification*
  • Limonins / chemistry*
  • Limonins / isolation & purification*
  • Meliaceae / chemistry*
  • Molecular Conformation
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Plant Bark / chemistry
  • Plant Stems / chemistry

Substances

  • Drugs, Chinese Herbal
  • Limonins