An important advantage of our approach, separating the roles of catalytic activity and selectivity, is the modular nature of the system. In such modular catalytic systems, it should be possible to vary the catalytic species, and maintain selectivity (though activity may vary). To establish this, we performed a series of reactions employing a range of solid acid catalysts (Montmorillonite, Graphene Oxide, MCM-41, SiO2), without further optimisation of conditions. We observe that in all cases where measurable yield is observed, selectivity remains almost constant, at around 90% ee. Very similar results were observed on varying the aldehyde to 2b (see SI, Table ).