NMR STUDY OF SOME ERYTHROMYCIN AGLYCONES . A CONFORMATIONAL AND CONFIGURATIONAL ANALYSIS

The proton magnetic resonance spectra of some erythromycin aglycones have been investigated at 100MHz in both deuteriochloroform and pyridine-d5 solvents. Utilizing information derived from pyridine solvent Δ-values (Δ= δCDCl3-δC5D5N) and spin-spin coupling constants for vicinal protons, the preferred approximate conformations of these 14-membered lactone ring systems in solution have been shown to be the same in III, IV, V and VI and to closely approximate the conformation previously derived from X-ray analysis for the aglycone ring in erythromycin A. The asymmetry at C-9 in dihydroaglycones IV, V and VI has been shown to be S in V and VI and R in IV. The utility of pyridine solvent shifts in the three-dimensional analysis of hydroxylic compounds is uniquely demonstrated in these polyhydroxy macrolides and emphasizes the potential of this technique for structure analysis. © 1969, JAPAN ANTIBIOTICS RESEARCH ASSOCIATION. All rights reserved.