Coenzyme F430 from Methanogenic Bacteria: Complete Assignment of Configuration Based on an X‐Ray Analysis of 12,13‐Diepi‐F430 Pentamethyl Ester and on NMR Spectroscopy

The structure of a derivative of coenzyme F430 from methanogenic bacteria, the bromide salt of 12,13‐diepi‐F430 pentamethyl ester ( 5 , X = Br), was determined by X‐ray structure analysis. It reveals a more pronounced saddle‐shaped out‐of‐plane deformation of the macrocycle than any hydroporphinoid Ni complex investigated so far. The crystal structure confirms the constitution proposed for coenzyme F430 ( 2 ) and shows that in the epimer 5 , the three stereogenic centers in ring D, C(17), C(18), and C(19), have the (17 S )‐, (18 S )‐, and (19 R )‐configuration, respectively. Deuteration and 2D‐NMR studies independently demonstrate that native coenzyme F430 (2) has the same configuration in ring D as the epimer 5 . Therefore, our original tentative assignment of configuration at C(19) and C(18) [1] has to be reversed. This completes the assignment of configuration for all stereogenic centers in coenzyme F430, which has the structure shown in Formula 2 .