Nature Chemistry, Published online: 01 June 2026; doi:10.1038/s41557-026-02156-z The availability of sterically hindered vicinal tetrasubstituted amino acids has long been a formidable challenge in medicinal chemistry due to their rigid structures. Now it has been shown that leveraging triplet nitrene reactivity and combining it with titanium catalysis enables access to these valuable building blocks from abundant carbonyls.