A process for producing a precursor compound for a radioactive fluorine-labeled organic compound, which comprises: a reaction step of giving a reaction condition to a solution containing a compound represented by the following formula: where, in formula, R 1 represents a protective group of a carboxyl group, and R 2 represents a protective group of an amino group, together with a base and a compound which reacts with the OH group of the compound represented by the formula to become a leaving group, and a purification step of purifying a reaction solution resulting from the reaction step to obtain a single stereoisomer of a compound represented by the following formula: where, in formula, R 1 represents a protective group of a carboxyl group, R 2 represents a protective group of an amino group, and OR 3 represents a leaving group, wherein the base in the reaction step is one or more selected from the group consisting of a straight-chain or branched-chain primary to tertiary alkylamine with 1-10 carbon atoms, a nitrogen-containing heterocyclic compound with 2-20 carbon atoms and a nitrogen-containing hetero aromatic compound with 2-20 carbon atoms, the compound which reacts with the OH group of the compound represented by the formula to become a leaving group in the reaction step is trifluoromethanesulfonic acid or trifluoromethanesulfonic anhydride, and the purification step is conducted by a liquid-liquid extraction process utilizing the difference in solubility between syn-leaving group adduct and the anti-leaving group adduct, wherein in said liquid-liquid extraction process water, an organic solvent and an acid are added to the reaction solution to purify the organic layer. a reaction step of giving a reaction condition to a solution containing a compound represented by the following formula: where, in formula, R 1 represents a protective group of a carboxyl group, and R 2 represents a protective group of an amino group, together with a base and a compound which reacts with the OH group of the compound represented by the formula to become a leaving group, and a purification step of purifying a reaction solution resulting from the reaction step to obtain a single stereoisomer of a compound represented by the following formula: where, in formula, R 1 represents a protective group of a carboxyl group, R 2 represents a protective group of an amino group, and OR 3 represents a leaving group, wherein the base in the reaction step is one or more selected from the group consisting of a straight-chain or branched-chain primary to tertiary alkylamine with 1-10 carbon atoms, a nitrogen-containing heterocyclic compound with 2-20 carbon atoms and a nitrogen-containing hetero aromatic compound with 2-20 carbon atoms, the compound which reacts with the OH group of the compound represented by the formula to become a leaving group in the reaction step is trifluoromethanesulfonic acid or trifluoromethanesulfonic anhydride, and the purification step is conducted by a liquid-liquid extraction process utilizing the difference in solubility between syn-leaving group adduct and the anti-leaving group adduct, wherein in said liquid-liquid extraction process water, an organic solvent and an acid are added to the reaction solution to purify the organic layer.