A process for producing an optically active 3-azide-carboxylic acid ester by
reacting
an optically active 3-hydroxycarboxylic acid ester and a thionyl halide in the
presence of a basic substance in an organic solvent to produce an optically active
3-halogenocarboxylic acid ester which is then reacted with an azide salt represented
by the formula: MN3 (wherein M is an alkaline metal) in water or a mixture
of water and a water soluble organic solvent.
