Structure of new alkaloids, evonine and neoevonine: X-ray analysis of bromoacetylneoevonine monohydrate

Abstract

The structures, and absolute configurations, of two Celastraceae alkaloids, evonine and neoevonine, isolated from Euonymus Sieboldiana Blume, have been established unambiguously by X-ray analysis of bromoacetylneoevonine. These alkaloids are characterized by the presence of a macrocyclic evoninic acid diester substituted on a highly oxygenated sesquiterpene nucleus. The crystals are monoclinic, space group P2₁, with Z= 2 in a unit cell of dimensions: a= 14·841(4), b= 14·645(4), c= 9·642(3)Å, β= 90·0(2)°. The structure was elucidated from diffractometer data by the heavy-atom method and the atomic co-ordinates were refined by Fourier and leastsquares calculations to R 0·091 for 1973 independent reflections. The absolute configuration was determined by the anomalous dispersion method and by comparison with the known absolute stereochemistry of the evoninic acid moiety.