3.2. Historical examples of bisindole structure identification by
NMR
In the beginning of the 1960s low-resolution (60 MHz),
continuous-wave (CW) NMR spectrometers were available,
enabling only the measurement of a 1H NMR spectrum of a
given analyte. Due to the insufficient spectral resolution, this
1H NMR spectrum allowed only fragmentary assignments of
resonances mostly belonging to some functional groups. The first
Fig.