The final possible simple form of conformational isomerism has been revealed by Peter Canfield, his supervisors Maxwell Crossley (University of Sydney) and Jeffrey Reimers (University of Technology Sydney and Shanghai University, China), their teams, and collaborators Elmars Krausz and Rika Kobayashi (ANU) (Canfield P.J., Blake I.M., Cai Z.-L., Luck I.J., Krausz E., Kobayashi R., Reimers J.R., Crossley M.J. Nat. Chem. 2018, 10, 615–24). Careful analysis of stereochemical interconversions led the team to consider that there was one unrecognised fundamental type of conformational isomerism remaining that, for example, could be produced by bond-angle inversion about centres of the form L–M–L linked only by single bonds. Calculations suggested that the bond-angle inversion reaction would occur in a constrained system in which the central atom would show an sp3 to sp to sp3 rehybridisation in the inversion sequence. This sequence was observed and studied in detail in a quinoxalino–porphyrin system with internal coordinated boron atoms in a 1,3-difluoro-1l4,3l4-diboroxan-1,1,3,3-tetrayl group ((BF)O(BF)), in which each boron is bonded in a transoid fashion to two adjacent pyrrolic nitrogen atoms. Four enantiomerically pure compounds were synthesised and their interconversions studied, each interconverting with complete stereoselectivity with an enantiomerically pure diasteromer (e.g. 1a and 2a) with ΔG‡ = 104 ± 2 kJ mol–1, ruling out all mechanisms but bond-angle inversion. The team has named the process akamptisomerisation and has introduced a new nomenclature to encompass such compounds.