Extended Data Fig. 1: Preparation of diamine 2 from norcorrole 1.

When 1 was treated with 1,3-dibromo-5,5-dimethylhydantoin, inseparable mono-, di- and tribrominated products were obtained. As bromination randomly occurred at positions 3, 7, 12 and 16 (that is, adjacent to the mesityl moieties), the 3,12- and 3,16-substituted dibromonorcorroles trans-1a and cis-1a were obtained as the main products (Supplementary Figs. 1, 2). Subsequently, disubstituted trans-1b and cis-1b were obtained by Suzuki–Miyaura cross-coupling at 43% yield as a mixture of two regioisomers (Supplementary Figs. 3, 4). Finally, 3,12-substituted subcomponent 2 could be isolated as a single regioisomer at 46% yield following reduction of the NO₂ groups and chromatography (Supplementary Figs. 5–9). Reagents and conditions: (i) 1,3-dibromo-5,5-dimethylhydantoin, CH₂Cl₂, −78 °C, 1 h, 94% (mixture of trans-1a, cis-1a and other brominated species). (ii) 4-Nitrophenylboronic acid pinacol ester, Pd(PPh₃)₄, K₃PO₄, dry THF, 70 °C, 1 h, 43% (mixture of trans-1b and cis-1b). (iii) SnCl₂·H₂O, dry THF, 70 °C, overnight, 46% (isolated 2).