Correction to: Nature https://doi.org/10.1038/s41586-019-1371-4Published online 10 July 2019

In Table 1 of this Letter, the percentage yields for the formation of Ac-AA-CN (entries 1–9), Ac-AA-SNH2 (entries 1–9) and Ac-AA-Gly-CN (entry 1) should have been ‘>99%’, to indicate essentially quantitative conversion of the starting material, rather than ‘99%’. Table 1 has been corrected online.