The geometry of the imine double bond at C-
7 was established by the comparison of the chemical shift and
the peak shape of the N–OH signal with those in the known bipyridine
analogue, SF2738A (3). In addition, a NOESY cross peak between
H-7 and S–CH3 established the conformation between C-6
and C-7. Overall, the structure of coprismycin A (1) was identified
as a previously unreported phenylpyridine.