If R-chiral carbonyl compounds are reacted with chiral nucleophiles, the issue of double sterecontrol arises. The analysis of such cases becomes therefore more complicated since it is very often not unambiguously possible to attribute the induced stereoselection to the R-chiral carbonyl substrate or to the nucleophile, respectively. Many situations are
encountered in which the nucleophile is rendered chiral by an auxiliary or a catalyst, which efficiently overrides the influence of the R-stereocenter in the substrate.