Abstract: The invention relates to a process for the preparation of 5-(1-hydroxy-2-urethanethylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione derivatives, which are precursors of chiral tetramic acid derivatives.According to this process, an N-urethane-protected .alpha.-amino acid N-carboxy-anhydride is reacted with Meldrum's acid in an inert organic solvent medium in the presence of a tertiary amine.This process makes it possible to conserve the chirality of the starting material and in particular to simplify the synthesis of 4-amino-3-hydroxy acids and the derivatives thereof via the tetramic acid route.