Issue 0, 1986

Structural and conformational studies on sesquiterpenoid esters from Laserpitium halleri Crantz subsp. halleri

Abstract

Investigation of the ripe fruits of Laserpitium halleri Crantz subsp. halleri afforded two pairs of new germacrane and guaiane esters, as well as the daucane derivative vaginatin, whose stereochemistry was assessed by spectral data and correlation with a compound of known configuration. The 1H and 13C n.m.r. spectra of the germacrane esters were characterized by the presence of sharp and broad signals. A conformational study of the natural compounds and several derivatives allowed us to relate the broadening of the n.m.r. lines to conformational motions which are discussed in detail. Among the derivatives of the natural esters, the ketone (8) was found to adopt in solution, a conformation hitherto unreported for germacrane derivatives [C(4) and C(10) methyls syn on the α-face of the molecule, C(7) side-chain β-axial]. Comparison of the spectral features of some crossed/boat germacra-1 (10),4-dienes and their corresponding 4,5-epoxides suggests that homoconjugation plays an important role in stabilizing the crossed/boat conformation of this class of cyclic 1,5-dienes. The biogenetic relationship between the compounds cumulated in the roots and the fruits of L. halleri is discussed.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 1, 1986, 1363-1372

Structural and conformational studies on sesquiterpenoid esters from Laserpitium halleri Crantz subsp. halleri

G. Appendino, M. G. Valle and P. Gariboldi, J. Chem. Soc., Perkin Trans. 1, 1986, 1363 DOI: 10.1039/P19860001363

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