The transmethylation process can provide a complex mass spectrum,
as in the case of leurosine-4-N-oxide [28]. In its EI-MS
spectrum the molecular ion peak at m/z 824, together with the
transmethylated ion of m/z 838, was detected; also the loss of the
N-oxide oxygen was observed through the ion peak of m/z 808
together with an ion peak m/z 822 derived from either m/z 838
by the loss of an oxygen or from m/z 808 by transmethylation.