Consequences of subtle chiral effects : from'Majority-Rules' to'Minority-Rules'

Mixing experiments were conducted on dilute solutions of asymmetrically substituted benzene-1,3,5-tricarboxamides (BTAs) with stereogenic methyl groups ranging from the a- to the d-position with respect to the amide in one of the three side groups. While normally the majority compound determines the helical sense preference of the formed supramolecular polymers, we find here that several combinations show a helical preference governed by the minority compound. BTAs with the methyl substituent at the a- and ¿-position overrule the helical preference of BTAs with the methyl substituent at the ß- and d-position. This new effect is referred to as a ‘minority-rules’ system.