he increase in antibiotic resistance raises concerns that, at least in some regions, we are returning to a pre-antibiotic era, in particular for Gram-negative infections. The increased prevalence of extended-spectrum serine-β-lactamases (SBLs) and metallo-β-lactamases (MBLs) means β-lactams are increasingly ineffective in treating Gram-negative infections 1,2 . The advent of mobilized colistin resistance-1 in 2015 3 and transferable tigecycline resistance genes (tetX3-tetX5) in 2019 4 , which mediate resistance to colistin and tigecycline, respectively, means all clinically vital antibiotics for serious Gram-negative infections are compromised.

Chiral, nonracemic 1,3-diamines were prepared in a highly diastereoselective reduction of diaryl N-tert-butanesulfinylketimines. Correlation between facial selectivity of the reduction and E or Z geometry of the starting ketimines suggests involvement of a cyclic transition state for the reduction. The ortho-substituent controls the geometry of N-tert-butanesulfinylketimines in the solid state and provides additional stabilization of the cyclic transition state.

Chiral, nonracemic o-aminobenzylamines were prepared in a highly diastereoselective reduction of atropisomeric N-tert-butanesulfinylketimines. The ortho-substituent ensures the distinct reactivity of atropisomers 4d-f. The free energy of activation for atropisomerization of sulfinylimines 4d-f in THF-d(8) was determined by NMR methods to range from 70.8 to 97.9 kJ/mol.

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