But on the basis of the differences in their fragmentation, the
two alkaloids could unambiguously be differentiated and some
structural insight could be drawn. In particular, a mass shift value
of 58 Da observed for the characteristic vindoline fragments (m/z
469 (A2)
→
m/z 411, m/z 282 (E)
→
m/z 224) and for the usual Retro Diels–Alder fragmentation (M+−160
→
M+−102) indicated that
the derivative in question was a desacetoxy compound instead
of a desacetyl one. Similar to that in leurocolombine, fragments B
and D were shifted by 16 Da, indicating the presence of an extra
oxygen atom in the alicyclic part of the velbanamine unit.