NMR studies of viomycin

The ¹H and ¹³C NMR spectra of antibiotic Viomycin sulphate and its constituent aminoacids in H₂O and D₂O were examined in a wide range of pH values. The spectra were analysed by proton spin-spin decoupling experiments and measurements of the relative intensities of the resonance and chemical shift values. Exchange experiments were also carried out and an almost complete assignment of the resonances of the spectra was possible. The data obtained are discussed in terms of possible structures for Viomycin and the presence of intramolecular hydrogen bonds. Some information about the conformation of the molecule is also given. A tentative assignment of the ¹³C spectrum of Viomycin is given and the experimental ¹³C chemical shift values compare well with the theoretical ones evaluated by Grant's rule.     

Further studies on palytoxin. I.

The structures of two degradation products of N-(p-bromobenzoyl) palytoxin were elucidated, and then the sequences of those fragments were determined.