Enantioselective synthesis by harnessing a non-equilibrium steady state. Using this perspective shift, it is possible to explain how, by harnessing a reaction network maintained at a non-equilibrium steady state, we can convert a racemic or achiral starting material to a highly enantioenriched mixture in up to 100% chemical yield. Several chemical strategies have been reported, 9 as well as examples that take advantage of photochemical steps 19 in the cycle. We shall demonstrate the principles that underly all such systems in the context of a minor enantiomer recycling (MER) reaction introduced by Moberg and co-workers. In the MER approach, formation of an acylated cyanohydrin by reaction of an aldehyde with acylcyanide is coupled to the overall hydrolysis of the same acylcyanide reagent (Figure ). This coupling is intuitively reasonable; formation of acylated cyanohydrin 4 by reaction of aldehyde 2 with acyl cyanide (3), followed by hydrolysis of 4 to regenerate 2 accomplishes the overall hydrolysis reaction (Figure c.f. Box 1.1), confirming that the aldehyde substrate mediates the coupled reaction. If the concentrations of 3, H2O, AcOH and HCN are chemostated to values inconsistent with Krxn, this coupling can potentially distort the steady state concentrations [2] and [4] from the values predicted by K1 (i.e., a non-equilibrium steady state is achieved), exactly as shown in our simple example (Box 1.1). Practically, this is not useful as product 4 will only accumulate if k+1 is a lot larger than k+2 and so product formation is maximized when hydrolysis is minimized. To see the power of this approach we must recognize: i. 4 is chiral and so the simple cycle (Figure ) can be rewritten as two enantiomeric networks (Figure ), ii. Although introducing a catalyst does not alter the corresponding equilibrium constant, it can distort the relative proportions of species at non-equilibrium steady as these depend on the corresponding rate constants. iii. Enantioselective catalysts can potentially influence the two enantiomeric networks differently, allowing one enantiomer to dominate. The authors demonstrated that introducing an enantioselective catalyst for the formation of (R)-4 (k+1R > k+1S) alongside an enzyme that stereoselectively hydrolyses (S)-4 (k+2R < k+2S) under conditions in which both reactions take place simultaneously gave (R)-4 in higher enantiomeric excess than either catalyst alone. One way of thinking about the role of the two catalysts is that the hydrolysis catalyst corrects the "mistakes" of the acylation catalyst, which intuitively could lead to higher selectivity (see ESI). Unlike classical approaches, in a well optimized system, the final enantiopurity, erfinal, can approach the product of the enantiopurities, er1er2, obtained in the individual reactions when run under comparable irreversible conditions and the yield can approach 100% (see ESI).