COMPLETE ASSIGNMENTS OF THE H-1 AND C-13 NMR-SPECTRA OF THE MACROLIDE ANTIBIOTIC FLAVOFUNGIN - INTRAMOLECULAR HYDROGEN-BONDING AND CONFORMATION

1H and 13C NMR spectra of the 32‐membered pentaene macrolide flavofungin‐I (identical with mycoticin A) in DMSO‐d6 solution were fully assigned employing a combination of various 1D and 2D homo‐ and hetero‐nuclear experiments. Secondary deuterium isotope shifts measured in the 1H NMR spectrum indicated that three of the eight hydroxyl groups are involved in intramolecular hydrogen bonds, which can lead to restricted mobility within the polyol part of the molecule. These results and inferences made from H, H coupling constants suggest that the conformation of the macrocycle is very similar to that found for roxaticin by x‐ray crystallography. All double bonds are in the E configuration, and the conjugated pentaene chain assumes a fully extended s‐trans conformation. Copyright © 1990 John Wiley & Sons, Ltd.