The coupling of these reactions can distort the relative concentrations of an Fmoc-carbonate and the corresponding alcohol even in a simple reaction network (Figure ). The final requirement to achieve continuous directed motion is kinetic asymmetry of the reaction cycle corresponding to pirouetting of the two rings in catenane 6 (Figure ). This arises because the rate constants for the reaction with FmocCl differ in the two coconformations of alcohol catenane 7; Fmoc-ester formation proceeds faster for 7(far) than 7(close) (i.e. (k+2(close) < k+2(far)). This results in net clockwise movement (as drawn) of the smaller ring, even though the major pathway of Fmoc cleavage occurs to give 7(far) and 7(close) with equal probability (k+1(close) = k+1(far)). The operation of catenane 6 at non-equilibrium steady state can be predicted mathematicallyindeed the equation for the ratchetting constant (eq. 3, Box 2) has the same form as that of eq. 2 (Box 1), despite the system appearing at first glance to be much more complicated. The authors demonstrated the operation of 6 by carrying out the individual steps of the cycle in a stepwise manner on an isotopomer of 6 in which one of the fumaramide stations was deuterated to allow the system to be monitored by 1 H NMR. They then demonstrated that both processes can proceed simultaneously to generate an autonomous motor.