The groups of Prof. Takeda (Hiroshima University) and Dr. Otani (The University of Tokyo) have come across a rather surprising outcome in the α-acylation of aminonitriles: under otherwise identical conditions, the choice of base (LDA vs. MHMDS) had a dramatic influence on the retention or inversion of the stereocentre.
Reference: Angew. Chem. Int. Ed. 2013, 12956-12960. link