The relative configurations of azalomycins F5a, F4a and F3a

Azalomycins F5a (1), F4a (2) and F3a (3) are three 36-membered polyhydroxyl macrolides with remarkable antifungal activity. By comparing the NMR spectral data of 1 and its degradation products with those of several universal NMR databases and identical fragments of known compounds, the relative configuration of 1 was assigned for the first time except that the stereochemistry of stereoclusters C6–C11 to C14–C36 was undefined. Moreover, the relative configurations of 2 and 3 were respectively established by comparing their NMR spectral data with those of 1.