Bisindole alkaloids aromatic substitution

In the cases of bisindole alkaloids which possess only one substituted aromatic position the seven-proton aromatic region of the n.m.r. spectrum needs to be well enough resolved to allow analysis. At 100 MHz this is the case for alkaloids of the pycnan thine group (Section 11) and pleiomutine (230) (Section 13, p. 279). The j5-carboline derivative serpentinine (253) contains ten aromatic protons and the 100 MHz spectrum yields little information in contrast, the 220 MHz spectrum... 

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