The structure of anadoline

The alkaloid previously isolated from Symphytum orientale and regarded as a diester of a new, doubly unsaturated pyrrolizidine diol with tiglic and trachelanthic acids, is shown to be a monoester of retronecine N-oxide. N.m.r. and mass spectral measurements and electrophoretic data show that the tiglic acid esterifies not the C 7- hydroxyl of the pyrrolizidine ring, but the secondary hydroxyl of the trachelanthate moiety. It is proposed that the name anadoline be given in future to the corresponding tertiary base.