Similarly to the comparison with regioselectivity, itero-and stereoselectivities are orthogonal but complementary since several stereoisomers may arise after each iteration of a reaction. A simple case such as a first-order nucleophilic substitution (SN1) performed on an enantiopure dibromoalkane can illustrate this complementarity between the two selectivities (Figure ). To describe completely the outcome of such reaction presenting both itero-and stereoselectivities, it is necessary to express both the iteromeric excess ite and the ratio of stereoisomers dr (or ee/de when applicable) for a given iteration i.