A previous study showed that together with the festuclavine synthase FgaFS, the old yellow enzyme FgaOx3 from Aspergillus fumigatus catalyzed the conversion of chanoclavine-I aldehyde to festuclavine in the biosynthesis of ergot alkaloids. In the absence of FgaFS, a mixture containing two compounds with a ratio of 7:3 was detected in the enzyme assay of FgaOx3. NMR experiments including (DQF)-COSY, HSQC, HMBC and NOESY identified their structures as E/Z isomers of N-methyl-N-[(5R,10R)-10-(2-oxo-propyl)-2,4,5,10-tetrahydrobenzo[cd]indol-5-yl]formamide and proved the migration of the formyl group at C-8 in chanoclavine I-aldehyde to N-6 in the identified products.
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