Two‐dimensional NMR spectroscopy of LL‐28249‐α, a potent macrolide anthelmintic: 13 C, 1 H chemical shift assignments and solution conformation

LL‐F28249‐α is a potent antiparasitic antibiotic produced by Streptomyces cyaneogriseus ssp. noncyanogenus . Its complete 13 C NMR spectral assignment based on two‐dimensional double‐quantum experiments in a sample at natural isotopic abundance is described. The proton NMR assignments were made from a combination of homonuclear and heteronuclear two‐dimensional correlation experiments. Proton‐proton scalar couplings, nuclear Over‐hauser enhancements and molecular mechanics energy minimization calculations are also reported, permitting a comparison of solution conformation with the known x‐ray structure adapted from a closely related analogue.