Having established and optimized the NR-triggered indazole formation reaction, we explored the substrate scope of NfsA and BaNTR1 for this transformation (Figure and Figures ). A conversion of >99 % was achieved for all substrates, except 1g, and 1a in the case of BaNTR1. The enzymes generally tolerate polar, non-polar and bulky R2 substitutions, whereas a methyl group on R1 strongly reduces activity. Although the indazole products are not chiral, both enzymes seem to prefer the (S)-enantiomer as a substrate, as indicated by the fact that the conversion of (rac)-1g is faster compared to (R)-1g. Nevertheless, at least in the case of NfsA, conversions of more than 50 % were achieved in the reaction of (rac)-1g, proving that both enantiomers can be converted. This behavior is advantageous in this particular case because the product of both enantiomers is accessible and thus racemic mixtures can be utilized. The substrate 1h did not lead to the expected products, as only the decarboxylated product (6a') was observed in this reaction. It is possible that decarboxylation is favored over deprotonation in the aromatization reaction of 5h. As expected, the R2-substituted substrates lead to 2Hindazoles, while the R2-unsubstituted substrates 1a and 1g lead to 1H-indazoles.