A stereodivergent preparation of α-quaternary serine/cysteine derivatives incorporating two adjacent stereogenic centers has been developed through Cu/Ir-catalyzed asymmetric allylation of 2-oxazoline-4-carboxylates and 2-thiazoline-4-carboxylates. Tuning the electronic effect is the key to enhancing the reactivity of 2-oxazoline-4-carboxylates and suppressing the undesired β-elimination. The salient feature of this protocol is that all four stereoisomers of α-quaternary serine and cysteine derivatives could be achieved from the identical starting materials through pairwise combination of two distinct chiral catalysts.