Studies on the Constituents of Aster tataricus L. IV

Structure of Shionone. (4). Reductive Products of Shionone and Dihydroshionone

Abstract

Reaction product of shionone (I) and dihydroshionone (II) by various reduction agents were examined and two pairs of epimers, epi-shionol (V) and shionol (VI) from I, and epi-dihydroshionol (III) and dihydroshionol (IV) from II, were found to be formed. Yield of these products is shown in Tables I and II. IV and VI, mainly obtained by reduction with sodium in amyl alcohol, have equatorial hydroxyl. Oxidation of equimolar mixture of III and IV with 0.5 equivalent of chromium trioxide and examination of the recovery rate of unreacted alcohol revealed that III has an axial hydroxyl group since III is more easily oxidized by chromium trioxide than IV, as shown in Table III. From these and previously obtained results, it was assumed that the carbonyl group in I and II was subject to steric hindrance, i.e. presence or methyl or alkyl group of axial orientation in the β-carbon of the carbonyl group.