Production method of isoxazolidinedione compound

A method for producing an oxazolylethanol derivative of the formula

• wherein R is an optionally substituted aromatic hydrocarbon group, an optionally substituted alicyclic hydrocarbon group, an optionally substituted heterocyclic group or an optionally substituted condensed heterocyclic group, or a salt thereof, comprising the steps of
• (a) reacting a compound [1]
• or a salt thereof in an aqueous solvent with a compound of the formula [2]
• wherein R is as defined above, in the presence of an inorganic base to give an aspartate derivative of the formula [3]
• wherein R is as defined above;
• (b) reacting this compound with acetic anhydride using dimethylaminopyridine as a catalyst in the presence of a base, followed by heating for decarboxylation to give a compound of the formula [4]
• wherein R is as defined above;
• (c) adding p-toluenesulfonic acid without isolating this compound to give an oxazolylacetate derivative of the formula [5]
• wherein R is as defined above;
• (d) reducing this compound in tetrahydrofuran in the presence of NaBH4 as a reducing agent and methanol as an activating agent.