Amplification of chirality: The "sergeants and soldiers" principle appliedto dynamic hydrogen-bonded assemblies

The amplification of supramolecular chirality has been studied in dynamic c hiral hydrogen-bonded assemblies 1(3). (CA)(6) using "Sergeants and Soldier s" experiments. Previously, we have shown that chiral centers present in ei ther the dimelamine component 1 or the cyanurate component CA quantitativel y induce one handedness (M or P) in the assembly. This offers the possibili ty to study the amplification of chirality under two different kinetic regi mes. When chiral dimelamines 1 are used, the exchange of chiral components and (M/P)-interconversion, i.e., interconversion between the (M)- and (P)-i somers of assembly 1(3). (CA)(6), take place via identical pathways (condit ion A). When chiral cyanurates CA are used, the exchange of chiral componen ts occurs much faster than (M/P)-interconversion (condition B). Experimenta lly, a much stronger chiral amplification is observed under condition B. Fo r example, the observed chiral amplification for a mixture of chiral and ac hiral components (40:60) is 46% under condition B and 32% under condition A . Kinetic models were developed to fit the experimental data and to simulat e chiral amplification in dynamic systems in general. These simulations sho w that it is theoretically possible that the diastereomeric excess in a dyn amic system is more than 99% with less than 1% chiral component present!.