Chiral catalysis-driven rotary molecular motors

The structural anisotropy necessary to distinguish clockwise from counterclockwise motions in motor-molecules continuously rotating about a covalent single bond has previously been supplied by chiral fuelling systems or by enzymes. Here we report a class of rotary motors in which, like motor proteins, structural asymmetry in the motor itself causes directional rotary catalysis. A single stereogenic centre in azaindole-phenylethanoic acid motors is sufficient to produce diastereomeric intermediates of atropisomeric conformations in the catalytic cycle, generating 8:1 clockwise:counterclockwise directional bias in the motor's rotary catalysis of diisopropylcarbodiimide hydration (motor substituent PhCH₂-). One enantiomer of a chiral hydrolysis promoter increases the directionality to 30:1 for clockwise rotation (motor substituent CH₃-), while the other enantiomer reverses the direction to 1:2 clockwise:counterclockwise. The experimental demonstration that a chiral molecular motor can be powered by a chemical fuel to rotate either with, or counter to, the motor's dominant power stroke informs the understanding of how chemical energy is transduced through catalysis, the fundamental process that powers biology.