P. Tyson et al., Solution structure and assignments of the H-1 and C-13 NMR spectra of erythromycin C in organic and aqueous solution, J CHEM R-S, (12), 1998, pp. 727-727A
Erythromycin C (1) has been shown to exist as a 4:5 equilibrium mixture of
the 9-ketone and 12,9-hemiacetal ring-chain tautomers in aqueous solution a
t ambient temperature.