Monocarbamates, Derived from (S)-2-(Dibenzylamino)butane-1,4-diol, and the Influence of the Second O-Protecting Group on the Regioselectivity of Deprotonation - Application to the Synthesis of the Boletus Toxin (2S,4S)-γ-Hydroxy-norvaline - Sendzik, Martin; Guarnieri, Walter; Hoppe, Dieter (Synthesis, 1998)