Summary. We have focused on a single example, but the general features of such systems are common; if a catalytic reaction network is coupled to a chemostated spontaneous process it is possible to generate a steady state in which the relative concentrations of species of interest are significantly perturbed. If this allows a desired species to be amplified, as with the MER system, this can be synthetically useful. This is of most obvious use in enantioselective synthesis, but this concept is of potential interest if a reaction network can give rise to any otherwise hard to access species.